TUT: add a multi-region finite-area example tutorial

- the old naming grew organically and was previously restricted
  by avoiding name collisions with volume fields, which resulted
  in some minor consistencies

Common solid shell naming:

  | Keyword  | Default     | Description  | Key(old) | Old Naming     |
  | -------- | ----------- | ------------ | -------- | -------------- |
  | h        | hs (suffix) | thickness    | h        | "h_" + region  |
  | T        | Ts (suffix) | temperature  | -        | "Ts_" + region |

Vibration shells:

  | Keyword  | Default     | Description  | Key(old) | Old Naming     |
  | -------- | ----------- | ------------ | -------- | -------------- |
  |  as      | as (suffix) | acceleration | -        | "as_" + region |
  |  ps      | ps (suffix) | pres on shell| -        | "ps_" + region |
  |  ws      | ws (suffix) | displacement | -        | "ws_" + region |
  |  qs      | qs (suffix  | source field | -        | "qs_" + region |

Other:

  | Keyword  | Default     | Description  | Key(old) |
  | -------- | ----------- | ------------ | -------- |
  | Tprimary | T   | temperature (volume) | T        |

Joule heating: (possibly breaking naming changes)

  | Field    | Name                     | Name(old)                |
  | -------- | ------------------------ | ------------------------ |
  |  V       | \<scope\>:V (suffix)     | \<scope\>:V + region     |
  |  sigma   | \<scope\>:sigma (suffix) | \<scope\>:sigma + region |

applications/test/UPstreamTraits/Test-UPstreamTraits.cxx

@@ -200,7 +200,7 @@ void printTypeName()
 
 
 template<class Type, bool UseTypeName = true>
-void printPstreamTraits(const std::string_view name = std::string_view())
+void printPstreamTraits(std::string_view name = std::string_view())
 {
     Info<< "========" << nl;
     Info<< "type: ";
@@ -299,6 +299,9 @@ void printPstreamTraits(const std::string_view name = std::string_view())
         // Use element or component type (or byte-wise) for data type
         using base = typename UPstream_dataType<Type>::base;
 
+        // The sizing factor is constexpr
+        constexpr std::streamsize count = UPstream_dataType<Type>::size(1);
+
         Info<< " : ";
         if constexpr (UseTypeName)
         {
@@ -311,8 +314,7 @@ void printPstreamTraits(const std::string_view name = std::string_view())
 
         Info<< " cmpt-type=";
         printDataTypeId(UPstream_dataType<Type>::datatype_id);
-        Info<< " count=" << UPstream_dataType<Type>::size(1);
-        Info<< nl;
+        Info<< " count=" << count << nl;
     }
 }
 
@@ -362,6 +364,24 @@ void print_data_opType(BinaryOp bop, std::string_view name)
 }
 
 
+
+template<class Type>
+int check_simple(std::string_view name = std::string_view())
+{
+    // The sizing factor is constexpr
+    constexpr std::streamsize count = UPstream_dataType<Type>::size(1);
+
+    static_assert
+    (
+        (count == 1),
+        "Code does not (yet) work with aggregate types"
+    );
+
+    Info<< "check_simple: " << name << ": " << count << nl;
+    return count;
+}
+
+
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 // Main program:
 
@@ -389,6 +409,8 @@ int main()
     printPstreamTraits<const float>();
     printPstreamTraits<floatVector>();
 
+    check_simple<floatVector>("vector<float>");
+
     printPstreamTraits<scalar>();
     printPstreamTraits<double>();
     printPstreamTraits<doubleVector>();

applications/test/faMeshesRegistry/Test-faMeshesRegistry.cxx

@@ -49,8 +49,7 @@ int main(int argc, char *argv[])
 
     Info<< "mesh 0: " << mesh.sortedNames() << nl;
 
-    faMeshesRegistry& reg =
-        const_cast<faMeshesRegistry&>(faMeshesRegistry::New(mesh));
+    auto& reg = const_cast<faMeshesRegistry&>(faMeshesRegistry::New(mesh));
 
     // faMeshesRegistry faReg = faMeshesRegistry(mesh);
 

applications/test/foamToEnsight-check/Make/files

@@ -1,3 +1,3 @@
-foamToEnsight-check.C
+foamToEnsight-check.cxx
 
 EXE = $(FOAM_USER_APPBIN)/foamToEnsight-check

applications/test/foamToEnsight-check/foamToEnsight-check.cxx

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2022-2023 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -203,6 +203,7 @@ int main(int argc, char *argv[])
     argList::addVerboseOption();
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
 
     argList::addBoolOption
     (
@@ -251,6 +252,14 @@ int main(int argc, char *argv[])
     // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
     // ------------------------------------------------------------------------
 
     #include "createNamedMeshes.H"
@@ -259,8 +268,8 @@ int main(int argc, char *argv[])
     /// #include "createMeshAccounting.H"
 
     PtrList<ensightMesh> ensightMeshes(regionNames.size());
-    PtrList<faMesh> meshesFa(regionNames.size());
-    PtrList<ensightFaMesh> ensightMeshesFa(regionNames.size());
+    List<PtrList<faMesh>> meshesFa(regionNames.size());
+    List<PtrList<ensightFaMesh>> ensightMeshesFa(regionNames.size());
 
     forAll(regionNames, regioni)
     {
@@ -273,21 +282,32 @@ int main(int argc, char *argv[])
         );
         ensightMeshes[regioni].verbose(optVerbose);
 
-
-        if (doFiniteArea)
+        if (!doFiniteArea)
         {
-            autoPtr<faMesh> faMeshPtr(faMesh::TryNew(mesh));
+            continue;
+        }
+
+        meshesFa[regioni].resize_null(areaRegionNames.size());
+        ensightMeshesFa[regioni].resize_null(areaRegionNames.size());
+
+        autoPtr<faMesh> faMeshPtr(faMesh::TryNew(mesh));
+
+        forAll(areaRegionNames, areai)
+        {
+            const word& areaName = areaRegionNames[areai];
+
+            autoPtr<faMesh> faMeshPtr(faMesh::TryNew(areaName, mesh));
 
             if (faMeshPtr)
             {
-                meshesFa.set(regioni, std::move(faMeshPtr));
+                meshesFa[regioni].set(areai, std::move(faMeshPtr));
 
-                ensightMeshesFa.set
+                ensightMeshesFa[regioni].set
                 (
-                    regioni,
-                    new ensightFaMesh(meshesFa[regioni])
+                    areai,
+                    new ensightFaMesh(meshesFa[regioni][areai])
                 );
-                ensightMeshesFa[regioni].verbose(optVerbose);
+                ensightMeshesFa[regioni][areai].verbose(optVerbose);
             }
         }
     }
@@ -295,7 +315,7 @@ int main(int argc, char *argv[])
     // ------------------------------------------------------------------------
 
 
-    if (Pstream::master())
+    if (UPstream::master())
     {
         Info<< "Checking " << timeDirs.size() << " time steps" << nl;
     }
@@ -317,17 +337,20 @@ int main(int argc, char *argv[])
             auto& ensMesh = ensightMeshes[regioni];
 
             // Finite-area (can be missing)
-            auto* ensFaMeshPtr = ensightMeshesFa.get(regioni);
+            auto& ensFaMeshes = ensightMeshesFa[regioni];
 
             if (moving)
             {
                 ensMesh.expire();
                 ensMesh.correct();
 
-                if (ensFaMeshPtr)
+                forAll(areaRegionNames, areai)
                 {
-                    ensFaMeshPtr->expire();
-                    ensFaMeshPtr->correct();
+                    if (auto* ensFaMeshPtr = ensFaMeshes.get(areai))
+                    {
+                        ensFaMeshPtr->expire();
+                        ensFaMeshPtr->correct();
+                    }
                 }
             }
 
@@ -340,9 +363,15 @@ int main(int argc, char *argv[])
 
                 printInfo(ensMesh, optVerbose);
 
-                if (ensFaMeshPtr)
+                // finite-area
+                forAll(areaRegionNames, areai)
                 {
-                    printInfo(*ensFaMeshPtr, optVerbose);
+                    auto* ensFaMeshPtr = ensFaMeshes.get(areai);
+
+                    if (ensFaMeshPtr)
+                    {
+                        printInfo(*ensFaMeshPtr, optVerbose);
+                    }
                 }
             }
         }

applications/test/sort/Test-sortList.cxx

@@ -296,7 +296,7 @@ int main(int argc, char *argv[])
             (
                 strings,
                 order,
-                stringOps::natural_sort::less<string>(strings)
+                stringOps::natural_sort::list_less(strings)
             );
             Info<< "natural sortedOrder: " << flatOutput(order) << endl;
         }
@@ -321,7 +321,7 @@ int main(int argc, char *argv[])
             ///  sortable = hashed.toc();
             ///  sortable.sort
             ///  (
-            ///      stringOps::natural_sort::less<string>(sortable)
+            ///      stringOps::natural_sort::list_less(sortable)
             ///  );
             ///  Info<< nl << "natural:" << sortable << endl;
 
@@ -329,7 +329,7 @@ int main(int argc, char *argv[])
             ///  sortable = hashed.toc();
             ///  sortable.sort
             ///  (
-            ///      stringOps::natural_sort::greater<string>(sortable)
+            ///      stringOps::natural_sort::list_greater(sortable)
             ///  );
             ///  Info<< nl << "natural:" << sortable << endl;
         }

applications/test/string_view1/Test-string_view1.cxx

@@ -59,11 +59,6 @@ int main(int argc, char *argv[])
                 << " type: " << typeid(cstr).name() << " len:" << len << nl;
 
             Info<< "    view: " << std::string_view(cstr) << nl;
-
-            Info<< "    span: "
-                << stdFoam::span<const char>(cstr, len) << nl;
-            Info<< "    span: "
-                << stdFoam::span<char>(const_cast<char*>(cstr), len) << nl;
         }
     }
 

applications/test/surface-sampling/Make/files

@@ -1,4 +1,4 @@
-mydebugSurfaceWriter.C
-Test-surface-sampling.C
+mydebugSurfaceWriter.cxx
+Test-surface-sampling.cxx
 
 EXE = $(FOAM_USER_APPBIN)/Test-surface-sampling

applications/test/surface-sampling/mydebugSurfaceWriter.cxx

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2022-2023 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -83,12 +83,10 @@ template<> struct narrowType<SymmTensor<double>>
     typedef SymmTensor<float> type;
 };
 
-// FIXME: Not sure why this one seems to be broken...
-//
-// template<> struct narrowType<Tensor<double>>
-// {
-//     typedef Tensor<float> type;
-// };
+template<> struct narrowType<Tensor<double>>
+{
+    typedef Tensor<float> type;
+};
 
 } // End namespace Foam
 
@@ -104,12 +102,18 @@ Foam::surfaceWriters::mydebugWriter::mergeField
 {
     addProfiling(merge, "debugWriter::merge-field");
 
-    // This is largely identical to surfaceWriter::mergeField()
+    // Identical to surfaceWriter::mergeField()
     // but with narrowing for communication
-    if (narrowTransfer_ && parallel_ && UPstream::parRun())
+
+    if constexpr (std::is_same_v<Tensor<double>, Type>)
+    {
+        // Cannot narrow tensor. Does not compile since MatrixSpace
+        // does not (yet) allow assigments from different Cmpt types.
+    }
+    else if (narrowTransfer_ && parallel_ && UPstream::parRun())
     {
         // The narrowed type
-        typedef typename narrowType<Type>::type narrowedType;
+        using narrowedType = typename narrowType<Type>::type;
 
         // Ensure geometry is also merged
         merge();
@@ -130,14 +134,29 @@ Foam::surfaceWriters::mydebugWriter::mergeField
         ConstPrecisionAdaptor<narrowedType, Type> input(fld);
         PrecisionAdaptor<narrowedType, Type> output(allFld);
 
-        globIndex.gather
-        (
-            input.cref(),   // fld,
-            output.ref(),   // allFld,
-            UPstream::msgType(),
-            commType_,
-            UPstream::worldComm
-        );
+        if (gatherv_)
+        {
+            globIndex.mpiGather
+            (
+                input.cref(),   // fld
+                output.ref(),   // allFld
+                UPstream::worldComm,
+                // For fallback:
+                commType_,
+                UPstream::msgType()
+            );
+        }
+        else
+        {
+            globIndex.gather
+            (
+                input.cref(),   // fld
+                output.ref(),   // allFld
+                UPstream::msgType(),
+                commType_,
+                UPstream::worldComm
+            );
+        }
 
         // Commit adapted content changes
         input.commit();
@@ -193,8 +212,19 @@ Foam::surfaceWriters::mydebugWriter::mydebugWriter
 {
     Info<< "Using debug surface writer ("
         << (this->isPointData() ? "point" : "face") << " data):"
-        << " commsType=" << UPstream::commsTypeNames[commType_]
-        << " merge=" << Switch::name(enableMerge_)
+        << " commsType=";
+
+    if (UPstream::parRun())
+    {
+        if (gatherv_) Info<< "gatherv+";
+        Info<< UPstream::commsTypeNames[commType_];
+    }
+    else
+    {
+        Info<< "serial";
+    }
+
+    Info<< " merge=" << Switch::name(enableMerge_)
         << " write=" << Switch::name(enableWrite_)
         << " narrow=" << Switch::name(narrowTransfer_)
         << endl;

applications/utilities/finiteArea/checkFaMesh/checkFaMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2021-2023 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -28,7 +28,7 @@ Application
     makeFaMesh
 
 Description
-    Check a finiteArea mesh
+    Check a finite-area mesh
 
 Original Authors
     Zeljko Tukovic, FAMENA
@@ -39,6 +39,7 @@ Original Authors
 #include "Time.H"
 #include "argList.H"
 #include "faMesh.H"
+#include "faMeshTools.H"
 #include "polyMesh.H"
 #include "areaFaMesh.H"
 #include "edgeFaMesh.H"
@@ -47,7 +48,7 @@ Original Authors
 #include "processorFaPatch.H"
 #include "foamVtkIndPatchWriter.H"
 #include "foamVtkLineWriter.H"
-#include "faMeshTools.H"
+#include "regionProperties.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -59,7 +60,7 @@ int main(int argc, char *argv[])
 {
     argList::addNote
     (
-        "Check a finiteArea mesh"
+        "Check a finite-area mesh"
     );
 
     argList::addBoolOption
@@ -77,9 +78,15 @@ int main(int argc, char *argv[])
     );
 
     #include "addRegionOption.H"
-    #include "addFaRegionOption.H"
+    #include "addAllFaRegionOptions.H"
     #include "setRootCase.H"
     #include "createTime.H"
+
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    // ------------------------------------------------------------------------
+
     #include "createNamedPolyMesh.H"
 
     int geometryOrder(1);
@@ -91,16 +98,41 @@ int main(int argc, char *argv[])
         faMesh::geometryOrder(geometryOrder);
     }
 
-    #include "createNamedFaMesh.H"
-
-    Info<< "Time = " << runTime.timeName() << nl << endl;
-
-    // Mesh information (verbose)
-    faMeshTools::printMeshChecks(aMesh);
-
-    if (args.found("write-vtk"))
+    for (const word& areaName : areaRegionNames)
     {
-        #include "faMeshWriteVTK.H"
+        Info<< "Create faMesh";
+        if (!polyMesh::regionName(areaName).empty())
+        {
+            Info<< " [" << areaName << "]";
+        }
+        Info<< " for time = " << runTime.timeName() << nl;
+
+        autoPtr<faMesh> faMeshPtr(faMesh::TryNew(areaName, mesh));
+
+        if (!faMeshPtr)
+        {
+            Info<< "    ...failed to create area-mesh";
+            if (!polyMesh::regionName(areaName).empty())
+            {
+                Info<< " [" << areaName << "]";
+            }
+            Info<< endl;
+            continue;
+        }
+        else
+        {
+            Info<< endl;
+        }
+
+        const auto& aMesh = faMeshPtr();
+
+        // Mesh information (verbose)
+        faMeshTools::printMeshChecks(aMesh);
+
+        if (args.found("write-vtk"))
+        {
+            #include "faMeshWriteVTK.H"
+        }
     }
 
     Info<< "\nEnd\n" << endl;

applications/utilities/finiteArea/checkFaMesh/faMeshWriteVTK.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021-2023 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -15,6 +15,16 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
+// The base name for output files
+word vtkBaseFileName(aMesh.regionName());
+if (polyMesh::regionName(vtkBaseFileName).empty())
+{
+    vtkBaseFileName = "finiteArea";
+}
+
+Info<< nl;
+Info<< "Write faMesh in vtk format:" << nl;
+
 {
     // finiteArea - faces
     vtk::uindirectPatchWriter writer
@@ -23,7 +33,7 @@ Description
         // vtk::formatType::INLINE_ASCII,
         fileName
         (
-            aMesh.time().globalPath() / "finiteArea"
+            aMesh.time().globalPath() / vtkBaseFileName
         )
     );
 
@@ -32,7 +42,7 @@ Description
     globalIndex procAddr(aMesh.nFaces());
     labelList cellIDs;
 
-    if (Pstream::master())
+    if (UPstream::master())
     {
         cellIDs.resize(procAddr.totalSize());
         for (const labelRange& range : procAddr.ranges())
@@ -53,8 +63,7 @@ Description
     writer.beginPointData(1);
     writer.write("normal", aMesh.pointAreaNormals());
 
-    Info<< nl
-        << "Wrote faMesh in vtk format: " << writer.output().name() << nl;
+    Info<< "    " << writer.output().name() << nl;
 }
 
 {
@@ -66,7 +75,7 @@ Description
         // vtk::formatType::INLINE_ASCII,
         fileName
         (
-            aMesh.time().globalPath() / "finiteArea-edges"
+            aMesh.time().globalPath() / (vtkBaseFileName + "-edges")
         )
     );
 
@@ -88,8 +97,7 @@ Description
     writer.beginPointData(1);
     writer.write("normal", aMesh.pointAreaNormals());
 
-    Info<< nl
-        << "Wrote faMesh in vtk format: " << writer.output().name() << nl;
+    Info<< "    " << writer.output().name() << nl;
 }
 
 {
@@ -108,7 +116,7 @@ Description
         // vtk::formatType::INLINE_ASCII,
         fileName
         (
-            aMesh.time().globalPath() / "finiteArea-edgesCentres"
+            aMesh.time().globalPath() / (vtkBaseFileName + "-edgesCentres")
         )
     );
 
@@ -134,8 +142,7 @@ Description
         writer.write("normal", fld);
     }
 
-    Info<< nl
-        << "Wrote faMesh in vtk format: " << writer.output().name() << nl;
+    Info<< "    " << writer.output().name() << nl;
 }
 
 

applications/utilities/finiteArea/makeFaMesh/checkPatchTopology.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2023 OpenCFD Ltd.
+    Copyright (C) 2023-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -15,7 +15,7 @@ Description
 
 Input
     mesh (polyMesh)
-    meshDefDict (system/faMeshDefintion)
+    meshDefDict (system/finite-area/faMeshDefinition)
 
 \*---------------------------------------------------------------------------*/
 
@@ -25,13 +25,16 @@ Input
 
     const polyBoundaryMesh& pbm = mesh.boundaryMesh();
 
-    wordRes polyPatchNames;
-    meshDefDict.readIfPresent("polyMeshPatches", polyPatchNames);
+    labelList patchIDs;
 
-    const labelList patchIDs
+    if
     (
-        pbm.indices(polyPatchNames, true)  // useGroups
-    );
+        wordRes select;
+        meshDefDict.readIfPresent("polyMeshPatches", select)
+    )
+    {
+        patchIDs = pbm.indices(select, true);  // useGroups
+    }
 
     label nFaceLabels = 0;
     for (const label patchi : patchIDs)

applications/utilities/finiteArea/makeFaMesh/findMeshDefinitionDict.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021-2024 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -13,6 +13,18 @@ License
 Description
     Search for the appropriate faMeshDefinition dictionary...
 
+    Expects to find a faMeshDefinition file in a location specified
+    by the command-line option, or one of the standard locations.
+
+    For default area region (region0):
+      (1) system/finite-area/faMeshDefinition
+      (2) system/faMeshDefinition  [legacy location - v2312 and earlier]
+
+    For a named area region:
+      (1) system/finite-area/<area-name>/faMeshDefinition
+      (2) system/finite-area/faMeshDefinition.<area-name>
+          [symmetric with faOptions]
+
 Required Classes
     - Foam::polyMesh
     - Foam::IOdictionary
@@ -24,81 +36,185 @@ Required Variables
     - runTime [Time]
 
 Provided Variables
-    - meshDefDict [IOdictionary]
-    - meshDictPtr [autoPtr<IOdictionary>]
+    - faMeshDefinitionPtr [autoPtr<IOdictionary>]
+
+If the dictionary cannot be found, exits with an error message or
+reports a warning (dry-run mode)
 
 \*---------------------------------------------------------------------------*/
 
 const word dictName("faMeshDefinition");
 
-autoPtr<IOdictionary> meshDictPtr;
+autoPtr<IOdictionary> faMeshDefinitionPtr;
 
 {
-    fileName dictPath;
-    const word& regionDir = Foam::polyMesh::regionName(regionName);
-    const word& areaRegionDir = Foam::polyMesh::regionName(areaRegionName);
+    // Exit unless dry-run?
+    const bool exitOnFailure = (!args.dryRun());
 
-    if (args.readIfPresent("dict", dictPath))
+    const word& regionDir = polyMesh::regionName(regionName);
+    const word& areaRegionDir = polyMesh::regionName(areaRegionName);
+
+    // Canonical location
+    fileName dictPath
+    (
+        runTime.system()/regionDir
+      / faMesh::prefix()/areaRegionDir/dictName
+    );
+
+
+    // Dictionary specified on the command-line ...
+    const bool specified = args.readIfPresent("dict", dictPath);
+
+    if (specified)
     {
-        // Dictionary specified on the command-line ...
-
         if (isDir(dictPath))
         {
             dictPath /= dictName;
         }
     }
-    else if
-    (
-        // Dictionary under system/faMeshDefinition ?
-        // (v2312 and earlier)
 
-        areaRegionDir.empty()
-     && exists
-        (
-            runTime.path()/runTime.caseSystem()
-          / regionDir/faMesh::meshSubDir/dictName
-        )
-    )
-    {
-        // Dictionary present directly in system/ (v2312 and earlier)
-
-        dictPath = runTime.system()/regionDir/dictName;
-    }
-    else
-    {
-        // Use system/finite-area/ directory, with region qualifications
-
-        dictPath =
-        (
-            runTime.system()/regionDir
-          / faMesh::prefix()/areaRegionDir/dictName
-        );
-    }
 
     IOobject meshDictIO
     (
         dictPath,
         runTime,
-        IOobject::MUST_READ,
-        IOobject::NO_WRITE,
-        IOobject::NO_REGISTER,
+        IOobjectOption::MUST_READ,
+        IOobjectOption::NO_WRITE,
+        IOobjectOption::NO_REGISTER,
         true    // is globalObject
     );
 
-    if (!meshDictIO.typeHeaderOk<IOdictionary>(true))
+    refPtr<IOobject> meshDictIOPtr;
+
+    bool foundIOobject = meshDictIO.typeHeaderOk<IOdictionary>(true);
+
+    // For reporting any alternative locations
+    dictPath.clear();
+
+    if (!foundIOobject && !specified)
     {
-        FatalErrorInFunction
-            << meshDictIO.objectPath() << nl
-            << exit(FatalError);
+        if (!areaRegionDir.empty())
+        {
+            // Alternative location
+            // - system/finite-area/faMeshDefinition.<area-name>
+
+            dictPath =
+            (
+                runTime.system()/regionDir
+              / faMesh::prefix()/IOobject::groupName(dictName, areaRegionDir)
+            );
+        }
+        else
+        {
+            // legacy location (v2312 and earlier)
+            // - system/faMeshDefinition
+
+            dictPath = runTime.system()/regionDir/dictName;
+        }
+
+        if (!dictPath.empty())
+        {
+            auto ioptr = autoPtr<IOobject>::New
+            (
+                dictPath,
+                runTime,
+                IOobjectOption::MUST_READ,
+                IOobjectOption::NO_WRITE,
+                IOobjectOption::NO_REGISTER,
+                true    // is globalObject
+            );
+
+            foundIOobject =
+            (
+                ioptr && ioptr->typeHeaderOk<IOdictionary>(true)
+            );
+
+            if (foundIOobject)
+            {
+                // Use if found
+                meshDictIOPtr = std::move(ioptr);
+            }
+
+            // Generally retain dictPath for error messages,
+            // but don't mention the really old legacy location
+            if (areaRegionDir.empty())
+            {
+                dictPath.clear();
+            }
+        }
     }
 
-    Info<< "Creating faMesh from definition: "
-        << meshDictIO.objectRelPath() << endl;
+    // Alternative location or regular location?
+    if (!meshDictIOPtr)
+    {
+        meshDictIOPtr.cref(meshDictIO);
+    }
+    const auto& io = meshDictIOPtr();
 
-    meshDictPtr = autoPtr<IOdictionary>::New(meshDictIO);
+
+    // Handle final success or failure
+    if (foundIOobject)
+    {
+        Info<< "----------------" << nl
+            << "Using area-mesh definition";
+        if (!areaRegionDir.empty())
+        {
+            Info<< " [" << areaRegionName << "]";
+        }
+
+        Info<< nl
+            << "    " << io.objectRelPath() << nl << endl;
+
+        faMeshDefinitionPtr = autoPtr<IOdictionary>::New(io);
+    }
+    else
+    {
+        // Failure
+
+        if (exitOnFailure)
+        {
+            auto& err =
+                FatalErrorInFunction
+                << "Did not find area-mesh definition";
+
+            if (!areaRegionDir.empty())
+            {
+                err<< " [" << areaRegionName << "]";
+            }
+
+            err << nl
+                << "    " << io.objectRelPath() << nl;
+
+            if (!dictPath.empty())
+            {
+                err << "    " << dictPath << nl;
+            }
+
+            FatalError<< exit(FatalError);
+        }
+        else
+        {
+            // dry-run: warning
+            auto& err =
+                Warning << nl
+                << "----------------" << nl
+                << "Did not find area-mesh definition";
+
+            if (!areaRegionDir.empty())
+            {
+                err << " [" << areaRegionName << "]";
+            }
+
+            err << nl
+                << "    " << io.objectRelPath() << nl;
+
+            if (!dictPath.empty())
+            {
+                err << "    " << dictPath << nl;
+            }
+        }
+    }
 }
 
-IOdictionary& meshDefDict = *meshDictPtr;
-
 
 // ************************************************************************* //

applications/utilities/finiteArea/makeFaMesh/makeFaMesh.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2016-2017 Wikki Ltd
-    Copyright (C) 2021-2023 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -40,7 +40,6 @@ Original Authors
 
 #include "Time.H"
 #include "argList.H"
-#include "OSspecific.H"
 #include "faMesh.H"
 #include "faMeshTools.H"
 #include "IOdictionary.H"
@@ -53,6 +52,7 @@ Original Authors
 #include "PtrListOps.H"
 #include "foamVtkLineWriter.H"
 #include "foamVtkIndPatchWriter.H"
+#include "regionProperties.H"
 #include "syncTools.H"
 #include "OBJstream.H"
 
@@ -104,12 +104,14 @@ int main(int argc, char *argv[])
     );
 
     #include "addRegionOption.H"
-    #include "addFaRegionOption.H"
+    #include "addAllFaRegionOptions.H"
+
     #include "setRootCase.H"
     #include "createTime.H"
     #include "createNamedPolyMesh.H"
 
-    #include "getFaRegionOption.H"
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
 
     const bool doDecompose = !args.found("no-decompose");
     const bool doDecompFields = !args.found("no-fields");
@@ -123,56 +125,83 @@ int main(int argc, char *argv[])
         Info<< "Skip decompose of finiteArea fields" << nl;
     }
 
-    // Reading faMeshDefinition dictionary
-    #include "findMeshDefinitionDict.H"
+    // ------------------------------------------------------------------------
 
-    // Inject/overwrite name for optional 'empty' patch
-    word patchName;
-    if (args.readIfPresent("empty-patch", patchName))
+    for (const word& areaRegionName : areaRegionNames)
     {
-        meshDefDict.add("emptyPatch", patchName, true);
-    }
+        // Reading faMeshDefinition dictionary
+        #include "findMeshDefinitionDict.H"
 
-    // Preliminary checks
-    #include "checkPatchTopology.H"
+        if (!faMeshDefinitionPtr)
+        {
+            if (args.dryRun())
+            {
+                break;
+            }
+            else
+            {
+                FatalErrorInFunction
+                    << "Did not find area-mesh definition"<< nl
+                    << exit(FatalError);
+            }
+        }
 
-    Info << "Create areaMesh";
-    if (!Foam::polyMesh::regionName(areaRegionName).empty())
-    {
-        Foam::Info << ' ' << areaRegionName;
-    }
-    Info << " for polyMesh at time = " << runTime.timeName() << nl;
+        auto& meshDefDict = (*faMeshDefinitionPtr);
 
-    // Create
-    faMesh aMesh(areaRegionName, mesh, meshDefDict);
 
-    // Mesh information (less verbose)
-    faMeshTools::printMeshChecks(aMesh, 0);
+        // Inject/overwrite name for optional 'empty' patch
+        if (word name; args.readIfPresent("empty-patch", name))
+        {
+            meshDefDict.add("emptyPatch", name, true);
+        }
 
-    if (args.found("write-edges-obj"))
-    {
-        #include "faMeshWriteEdgesOBJ.H"
-    }
+        // Preliminary checks
+        #include "checkPatchTopology.H"
 
-    if (args.found("write-vtk"))
-    {
-        #include "faMeshWriteVTK.H"
-    }
+        Info<< "Create area-mesh";
+        if (!polyMesh::regionName(areaRegionName).empty())
+        {
+            Info<< " [" << areaRegionName << "]";
+        }
+        Info<< " with polyMesh at time = " << runTime.timeName() << nl;
 
-    if (args.dryRun())
-    {
-        Info<< "\ndry-run: not writing mesh or decomposing fields\n" << nl;
-    }
-    else
-    {
-        // More precision (for points data)
-        IOstream::minPrecision(10);
+        // Create
+        faMesh aMesh(areaRegionName, mesh, meshDefDict);
 
-        Info<< nl << "Write finite area mesh." << nl;
-        aMesh.write();
+        // Mesh information (less verbose)
+        faMeshTools::printMeshChecks(aMesh, 0);
 
-        Info<< endl;
-        #include "decomposeFaFields.H"
+        if (args.found("write-edges-obj"))
+        {
+            #include "faMeshWriteEdgesOBJ.H"
+        }
+
+        if (args.found("write-vtk"))
+        {
+            #include "faMeshWriteVTK.H"
+        }
+
+        if (args.dryRun())
+        {
+            Info<< "\ndry-run: not writing mesh or decomposing fields\n" << nl;
+        }
+        else
+        {
+            // More precision (for points data)
+            IOstream::minPrecision(10);
+
+            Info<< nl << "Write finite area mesh";
+            if (const word& name = aMesh.regionName(); !name.empty())
+            {
+                Info<< " [" << name << "]";
+            }
+            Info<< nl;
+
+            aMesh.write();
+
+            Info<< endl;
+            #include "decomposeFaFields.H"
+        }
     }
 
     Info<< "\nEnd\n" << endl;

applications/utilities/miscellaneous/foamListRegions/foamListRegions.C

@@ -30,7 +30,8 @@ Group
     grpPostProcessingUtilities
 
 Description
-    List regions from constant/regionProperties.
+    List volume regions from constant/regionProperties
+    or area regions from constant/finite-area/regionProperties
 
 Usage
     \b foamListRegions [OPTION]
@@ -72,6 +73,12 @@ int main(int argc, char *argv[])
         "List constant/finite-area/regionProperties (if available)"
     );
 
+    argList::addBoolOption
+    (
+        "optional",
+        "A missing regionProperties is not treated as an error"
+    );
+
     argList::addDryRunOption
     (
         "Make reading optional and add verbosity"
@@ -92,14 +99,20 @@ int main(int argc, char *argv[])
         ++optVerbose;
     }
 
+    // File is optional, not an error
+    const bool isOptional = args.found("optional");
+
     // Use finite-area regions
     const bool doFiniteArea = args.found("finite-area");
 
+    // The number of optional region filters to apply
+    const label nFilters = (args.size()-1);
+
     IOobjectOption::readOption readOpt(IOobjectOption::MUST_READ);
 
-    if (dryRun || doFiniteArea)
+    if (dryRun || isOptional || doFiniteArea)
     {
-        // Always treat finite-area regionProperties as optional
+        // The finite-area regionProperties are also considered optional
         readOpt = IOobjectOption::READ_IF_PRESENT;
     }
 
@@ -116,58 +129,70 @@ int main(int argc, char *argv[])
     if (doFiniteArea)
     {
         regionProps = regionProperties(runTime, faMeshPrefix, readOpt);
-
-        if (regionProps.empty())
-        {
-            InfoErr<< "No finite-area region types" << nl;
-        }
-        else if (optVerbose)
-        {
-            InfoErr
-                << "Have " << regionProps.size()
-                << " finite-area region types, "
-                << regionProps.count() << " regions" << nl << nl;
-        }
     }
     else
     {
         regionProps = regionProperties(runTime, readOpt);
-
-        if (regionProps.empty())
-        {
-            // Probably only occurs with -dry-run option
-            InfoErr<< "No region types" << nl;
-        }
-        else if (optVerbose)
-        {
-            InfoErr
-                << "Have " << regionProps.size() << " region types, "
-                << regionProps.count() << " regions" << nl << nl;
-        }
     }
 
-    // We now handle checking args and general sanity etc.
-    wordList regionTypes;
-
-    if (args.size() > 1)
+    // Some reporting...
+    if (regionProps.empty())
     {
-        regionTypes.resize(args.size()-1);
+        if (doFiniteArea)
+        {
+            InfoErr<< "No finite-area region types" << nl;
+        }
+        else if (isOptional)
+        {
+            InfoErr<< "No region types" << nl;
+        }
+    }
+    else if (optVerbose)
+    {
+        InfoErr << "Have " << regionProps.size();
 
-        // No duplicates
+        if (doFiniteArea)
+        {
+            InfoErr<< " finite-area";
+        }
+        InfoErr
+            << " region types, "
+            << regionProps.count() << " regions" << nl << nl;
+    }
+
+
+    // We now handle checking args and general sanity etc.
+
+    DynamicList<word> regionTypes;
+
+    if (isOptional && regionProps.empty())
+    {
+        // Nothing to do...
+    }
+    else if (nFilters > 0)
+    {
+        // Apply region filters
+
+        regionTypes.reserve_exact
+        (
+            Foam::min(nFilters, regionProps.size())
+        );
+
+        // No duplicates, and no duplicate warnings
         wordHashSet uniq;
 
-        label nTypes = 0;
         for (label argi = 1; argi < args.size(); ++argi)
         {
-            regionTypes[nTypes] = args[argi];
-
-            const word& regType = regionTypes[nTypes];
+            word regType(args[argi]);
 
             if (uniq.insert(regType))
             {
                 if (regionProps.contains(regType))
                 {
-                    ++nTypes;
+                    if (!regionTypes.contains(regType))
+                    {
+                        regionTypes.push_back(std::move(regType));
+                    }
                 }
                 else
                 {
@@ -175,22 +200,22 @@ int main(int argc, char *argv[])
                 }
             }
         }
-
-        regionTypes.resize(nTypes);
     }
     else
     {
+        // Take all regions
         regionTypes = regionProps.sortedToc();
     }
 
 
     for (const word& regionType : regionTypes)
     {
-        const wordList& regionNames = regionProps[regionType];
-
-        for (const word& regionName : regionNames)
+        if (const auto iter = regionProps.cfind(regionType); iter.good())
         {
-            Info<< regionName << nl;
+            for (const word& regionName : iter.val())
+            {
+                Info<< regionName << nl;
+            }
         }
     }
 

applications/utilities/parallelProcessing/decomposePar/decomposePar.C

@@ -334,6 +334,7 @@ int main(int argc, char *argv[])
     );
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
 
     argList::addDryRunOption
     (
@@ -418,8 +419,14 @@ int main(int argc, char *argv[])
     // Allow explicit -constant, have zero from time range
     timeSelector::addOptions(true, false);  // constant(true), zero(false)
 
+    // Prevent volume BCs from triggering finite-area
+    regionModels::allowFaModels(false);
+
     #include "setRootCase.H"
 
+    // ------------------------------------------------------------------------
+    // Configuration
+
     const bool writeCellDist    = args.found("cellDist");
 
     // Most of these are ignored for dry-run (not triggered anywhere)
@@ -436,7 +443,6 @@ int main(int argc, char *argv[])
     bool decomposeFieldsOnly = args.found("fields");
     bool forceOverwrite      = args.found("force");
 
-
     // Set time from database
     #include "createTime.H"
 
@@ -485,9 +491,17 @@ int main(int argc, char *argv[])
         decompDictFile = runTime.globalPath()/decompDictFile;
     }
 
-    // Get region names
+    // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
     const bool optRegions =
         (regionNames.size() != 1 || regionNames[0] != polyMesh::defaultRegion);
 
@@ -807,56 +821,76 @@ int main(int argc, char *argv[])
 
                 // Field objects at this time
                 IOobjectList objects;
-                IOobjectList faObjects;
+
+                // faMesh fields - can have multiple finite-area per volume
+                HashTable<IOobjectList> faObjects;
 
                 if (doDecompFields)
                 {
                     // List of volume mesh objects for this instance
                     objects = IOobjectList(mesh, runTime.timeName());
 
-                    // List of area mesh objects (assuming single region)
-                    faObjects = IOobjectList
-                    (
-                        mesh.time(),
-                        runTime.timeName(),
-                        faMesh::dbDir(mesh, word::null),
-                        IOobjectOption::NO_REGISTER
-                    );
-
                     // Ignore generated fields: (cellDist)
                     objects.remove("cellDist");
+
+                    // Lists of finite-area fields
+                    faObjects.reserve(areaRegionNames.size());
+
+                    for (const word& areaName : areaRegionNames)
+                    {
+                        // The finite-area objects for this area region
+                        IOobjectList objs
+                        (
+                            faMesh::Registry(mesh),
+                            runTime.timeName(),
+                            polyMesh::regionName(areaName),
+                            IOobjectOption::NO_REGISTER
+                        );
+
+                        if (!objs.empty())
+                        {
+                            faObjects.emplace_set(areaName, std::move(objs));
+                        }
+                    }
                 }
 
                 // Finite area handling
-                autoPtr<faMeshDecomposition> faMeshDecompPtr;
+                // - all area regions use the same volume decomposition
+
+                HashPtrTable<faMeshDecomposition> faMeshDecompHashes;
                 if (doFiniteArea)
                 {
                     const word boundaryInst =
                         mesh.time().findInstance(mesh.meshDir(), "boundary");
 
-                    IOobject io
-                    (
-                        "faBoundary",
-                        boundaryInst,
-                        faMesh::meshDir(mesh, word::null),
-                        mesh.time(),
-                        IOobject::READ_IF_PRESENT,
-                        IOobject::NO_WRITE,
-                        IOobject::NO_REGISTER
-                    );
-
-                    if (io.typeHeaderOk<faBoundaryMesh>(true))
+                    for (const word& areaName : areaRegionNames)
                     {
-                        // Always based on the volume decomposition!
-                        faMeshDecompPtr.reset
+                        IOobject io
                         (
-                            new faMeshDecomposition
-                            (
-                                mesh,
-                                mesh.nProcs(),
-                                mesh.model()
-                            )
+                            "faBoundary",
+                            boundaryInst,
+                            faMesh::meshDir(mesh, areaName),
+                            mesh.time(),
+                            IOobject::READ_IF_PRESENT,
+                            IOobject::NO_WRITE,
+                            IOobject::NO_REGISTER
                         );
+
+                        if (io.typeHeaderOk<faBoundaryMesh>(true))
+                        {
+                            // Always based on the volume decomposition!
+                            faMeshDecompHashes.set
+                            (
+                                areaName,
+                                autoPtr<faMeshDecomposition>::New
+                                (
+                                    areaName,
+                                    mesh,
+                                    mesh.nProcs(),
+                                    mesh.model()
+                                )
+                            );
+                        }
                     }
                 }
 
@@ -1060,7 +1094,7 @@ int main(int argc, char *argv[])
 
                     processorDb.setTime(runTime);
 
-                    // read the mesh
+                    // Read the mesh
                     if (!procMeshList.set(proci))
                     {
                         procMeshList.set
@@ -1267,12 +1301,15 @@ int main(int argc, char *argv[])
                 }
 
 
-                // Finite area mesh and field decomposition
-                if (faMeshDecompPtr)
+                // Finite-area mesh and field decomposition
+                for (auto& iter : faMeshDecompHashes.sorted())
                 {
-                    Info<< "\nFinite area mesh decomposition" << endl;
+                    const word& areaName = iter.key();
 
-                    faMeshDecomposition& aMesh = faMeshDecompPtr();
+                    faMeshDecomposition& aMesh = *(iter.val());
+
+                    Info<< "\nFinite area mesh decomposition: "
+                        << areaName << endl;
 
                     aMesh.decomposeMesh();
                     aMesh.writeDecomposition();
@@ -1283,9 +1320,13 @@ int main(int argc, char *argv[])
 
                     faFieldDecomposer::fieldsCache areaFieldCache;
 
-                    if (doDecompFields)
+                    if
+                    (
+                        const auto objs = faObjects.cfind(areaName);
+                        doDecompFields && objs.good()
+                    )
                     {
-                        areaFieldCache.readAllFields(aMesh, faObjects);
+                        areaFieldCache.readAllFields(aMesh, objs.val());
                     }
 
                     const label nAreaFields = areaFieldCache.size();
@@ -1316,7 +1357,7 @@ int main(int argc, char *argv[])
 
                         processorDb.setTime(runTime);
 
-                        // Read the mesh
+                        // Read the volume mesh
                         fvMesh procFvMesh
                         (
                             IOobject
@@ -1327,7 +1368,7 @@ int main(int argc, char *argv[])
                             )
                         );
 
-                        faMesh procMesh(procFvMesh);
+                        faMesh procMesh(areaName, procFvMesh);
 
                         // // Does not work.  HJ, 15/Aug/2017
                         // const labelIOList& faceProcAddressing =
@@ -1386,7 +1427,11 @@ int main(int argc, char *argv[])
                             boundaryProcAddressing
                         );
 
-                        areaFieldCache.decomposeAllFields(fieldDecomposer);
+                        areaFieldCache.decomposeAllFields
+                        (
+                            fieldDecomposer,
+                            args.verbose()  // report
+                        );
                     }
                 }
             }

applications/utilities/parallelProcessing/reconstructPar/reconstructPar.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2023 OpenCFD Ltd.
+    Copyright (C) 2015-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -91,6 +91,7 @@ int main(int argc, char *argv[])
     argList::noParallel();
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
 
     argList::addVerboseOption();
     argList::addOption
@@ -135,9 +136,14 @@ int main(int argc, char *argv[])
         "Only reconstruct new times (i.e. that do not exist already)"
     );
 
+    // Prevent volume BCs from triggering finite-area
+    regionModels::allowFaModels(false);
+
     #include "setRootCase.H"
     #include "createTime.H"
 
+    // ------------------------------------------------------------------------
+    // Configuration
 
     const bool doFields = !args.found("no-fields");
     wordRes selectedFields;
@@ -196,9 +202,17 @@ int main(int argc, char *argv[])
 
     const bool newTimes = args.found("newTimes");
 
-    // Get region names
+    // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
     // Determine the processor count
     label nProcs{0};
 
@@ -386,19 +400,30 @@ int main(int argc, char *argv[])
                 IOobjectOption::NO_REGISTER
             );
 
-            IOobjectList faObjects;
+            // The finite-area fields (multiple finite-area per volume)
+            HashTable<IOobjectList> faObjects;
 
             if (doFiniteArea && doFields)
             {
-                // List of area mesh objects (assuming single region)
-                // - scan on processor0
-                faObjects = IOobjectList
-                (
-                    procMeshes.meshes()[0],
-                    databases[0].timeName(),
-                    faMesh::dbDir(word::null),  // local relative to mesh
-                    IOobjectOption::NO_REGISTER
-                );
+                // Lists of finite-area fields - scan on processor0
+                faObjects.reserve(areaRegionNames.size());
+
+                for (const word& areaName : areaRegionNames)
+                {
+                    // The finite-area objects for this area region
+                    IOobjectList objs
+                    (
+                        procMeshes.meshes()[0],
+                        databases[0].timeName(),
+                        faMesh::dbDir(areaName),  // local relative to mesh
+                        IOobjectOption::NO_REGISTER
+                    );
+
+                    if (!objs.empty())
+                    {
+                        faObjects.emplace_set(areaName, std::move(objs));
+                    }
+                }
             }
 
             if (doFields)
@@ -548,42 +573,60 @@ int main(int argc, char *argv[])
             }
 
 
-            // If there are any FA fields, reconstruct them
-
-            if (!doFiniteArea)
+            // Reconstruct any finite-area fields
+            if (doFiniteArea)
             {
+                bool hadFaFields = false;
+                for (const word& areaName : areaRegionNames)
+                {
+                    const auto objs = faObjects.cfind(areaName);
+                    if (!objs.good())
+                    {
+                        continue;
+                    }
+                    const auto& faObjs = objs.val();
+
+                    if
+                    (
+                        !faObjs.count(fieldTypes::is_area)
+                     && !faObjs.count<edgeScalarField>()
+                    )
+                    {
+                        continue;
+                    }
+
+                    hadFaFields = true;
+
+                    Info<< "Reconstructing finite-area fields ["
+                        << polyMesh::regionName(areaName)
+                        << "]" << nl << endl;
+
+                    const faMesh aMesh(areaName, mesh);
+
+                    processorFaMeshes procFaMeshes
+                    (
+                        procMeshes.meshes(),
+                        areaName
+                    );
+
+                    faFieldReconstructor reconstructor
+                    (
+                        aMesh,
+                        procFaMeshes.meshes(),
+                        procFaMeshes.edgeProcAddressing(),
+                        procFaMeshes.faceProcAddressing(),
+                        procFaMeshes.boundaryProcAddressing()
+                    );
+
+                    reconstructor.reconstructAllFields(faObjs);
+                }
+
+                if (!hadFaFields)
+                {
+                    Info << "No finite-area fields" << nl << endl;
+                }
             }
-            else if
-            (
-                faObjects.count<areaScalarField>()
-             || faObjects.count<areaVectorField>()
-             || faObjects.count<areaSphericalTensorField>()
-             || faObjects.count<areaSymmTensorField>()
-             || faObjects.count<areaTensorField>()
-             || faObjects.count<edgeScalarField>()
-            )
-            {
-                Info << "Reconstructing FA fields" << nl << endl;
 
-                faMesh aMesh(mesh);
-
-                processorFaMeshes procFaMeshes(procMeshes.meshes());
-
-                faFieldReconstructor reconstructor
-                (
-                    aMesh,
-                    procFaMeshes.meshes(),
-                    procFaMeshes.edgeProcAddressing(),
-                    procFaMeshes.faceProcAddressing(),
-                    procFaMeshes.boundaryProcAddressing()
-                );
-
-                reconstructor.reconstructAllFields(faObjects);
-            }
-            else
-            {
-                Info << "No FA fields" << nl << endl;
-            }
 
             if (doReconstructSets)
             {

applications/utilities/parallelProcessing/reconstructParMesh/reconstructParMesh.C

@@ -119,17 +119,10 @@ autoPtr<faceCoupleInfo> determineCoupledFaces
         const polyBoundaryMesh& masterPatches = masterMesh.boundaryMesh();
 
 
-        DynamicList<label> masterFaces
-        (
-            masterMesh.nFaces()
-          - masterMesh.nInternalFaces()
-        );
+        DynamicList<label> masterFaces(masterMesh.nBoundaryFaces());
 
-
-        forAll(masterPatches, patchi)
+        for (const polyPatch& pp : masterPatches)
         {
-            const polyPatch& pp = masterPatches[patchi];
-
             if (isA<processorPolyPatch>(pp))
             {
                 for
@@ -139,11 +132,8 @@ autoPtr<faceCoupleInfo> determineCoupledFaces
                     proci++
                 )
                 {
-                    const string toProcString("to" + name(proci));
-                    if (
-                        pp.name().rfind(toProcString)
-                     == (pp.name().size()-toProcString.size())
-                    )
+                    const string toProcString("to" + Foam::name(proci));
+                    if (pp.name().ends_with(toProcString))
                     {
                         label meshFacei = pp.start();
                         forAll(pp, i)
@@ -156,7 +146,6 @@ autoPtr<faceCoupleInfo> determineCoupledFaces
 
             }
         }
-        masterFaces.shrink();
 
 
         // Pick up all patches on meshToAdd ending in "procBoundaryDDDtoYYY"
@@ -164,16 +153,10 @@ autoPtr<faceCoupleInfo> determineCoupledFaces
 
         const polyBoundaryMesh& addPatches = meshToAdd.boundaryMesh();
 
-        DynamicList<label> addFaces
-        (
-            meshToAdd.nFaces()
-          - meshToAdd.nInternalFaces()
-        );
+        DynamicList<label> addFaces(meshToAdd.nBoundaryFaces());
 
-        forAll(addPatches, patchi)
+        for (const polyPatch& pp : addPatches)
         {
-            const polyPatch& pp = addPatches[patchi];
-
             if (isA<processorPolyPatch>(pp))
             {
                 bool isConnected = false;
@@ -215,7 +198,6 @@ autoPtr<faceCoupleInfo> determineCoupledFaces
                 }
             }
         }
-        addFaces.shrink();
 
         return autoPtr<faceCoupleInfo>::New
         (
@@ -502,15 +484,14 @@ void writeMaps
 
     Info<< "    pointProcAddressing" << endl;
     ioAddr.rename("pointProcAddressing");
-    IOList<label>::writeContents(ioAddr, pointProcAddressing);
+    labelIOList::writeContents(ioAddr, pointProcAddressing);
 
     // From processor face to reconstructed mesh face
-    Info<< "    faceProcAddressing" << endl;
-    ioAddr.rename("faceProcAddressing");
-    labelIOList faceProcAddr(ioAddr, faceProcAddressing);
+    // - add turning index to faceProcAddressing.
+    //   See reconstructPar for meaning of turning index.
+
+    labelList faceProcAddr(faceProcAddressing);
 
-    // Now add turning index to faceProcAddressing.
-    // See reconstructPar for meaning of turning index.
     forAll(faceProcAddr, procFacei)
     {
         const label masterFacei = faceProcAddr[procFacei];
@@ -545,19 +526,21 @@ void writeMaps
         }
     }
 
-    faceProcAddr.write();
-
+    Info<< "    faceProcAddressing" << endl;
+    ioAddr.rename("faceProcAddressing");
+    labelIOList::writeContents(ioAddr, faceProcAddr);
+    faceProcAddr.clear();
 
     // From processor cell to reconstructed mesh cell
     Info<< "    cellProcAddressing" << endl;
     ioAddr.rename("cellProcAddressing");
-    IOList<label>::writeContents(ioAddr, cellProcAddressing);
+    labelIOList::writeContents(ioAddr, cellProcAddressing);
 
 
     // From processor patch to reconstructed mesh patch
     Info<< "    boundaryProcAddressing" << endl;
     ioAddr.rename("boundaryProcAddressing");
-    IOList<label>::writeContents(ioAddr, boundProcAddressing);
+    labelIOList::writeContents(ioAddr, boundProcAddressing);
 
     Info<< endl;
 }
@@ -645,7 +628,8 @@ void sortFaEdgeMapping
 {
     // From faMeshReconstructor.C - edge shuffling on patches
 
-    Map<label> remapGlobal(2*onePatch.nEdges());
+    Map<label> remapGlobal;
+    remapGlobal.reserve(onePatch.nEdges());
     for (label edgei = 0; edgei < onePatch.nInternalEdges(); ++edgei)
     {
         remapGlobal.insert(edgei, remapGlobal.size());
@@ -779,12 +763,23 @@ int main(int argc, char *argv[])
     );
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
+
+    // Prevent volume fields [with regionFaModels] from incidental
+    // triggering finite-area
+    regionModels::allowFaModels(false);
+
+    // Prevent volume BCs from triggering finite-area
+    regionModels::allowFaModels(false);
 
     #include "setRootCase.H"
     #include "createTime.H"
 
     printWarning();
 
+    // ------------------------------------------------------------------------
+    // Configuration
+
     const bool fullMatch = args.found("fullMatch");
     const bool procMatch = args.found("procMatch");
     const bool writeCellDist = args.found("cellDist");
@@ -835,9 +830,17 @@ int main(int argc, char *argv[])
         }
     }
 
-    // Get region names
+    // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
     // Determine the processor count
     label nProcs{0};
 
@@ -929,7 +932,8 @@ int main(int argc, char *argv[])
                 polyMesh::meshDir(regionName),
                 databases[0],
                 IOobject::NO_READ,
-                IOobject::NO_WRITE
+                IOobject::NO_WRITE,
+                IOobject::NO_REGISTER
             );
 
             // Problem: faceCompactIOList recognises both 'faceList' and
@@ -1399,8 +1403,12 @@ int main(int argc, char *argv[])
 
 
             // Read finite-area
-            PtrList<faMesh> procFaMeshes(databases.size());
+            // For each named area region that exists create a HashTable
+            // entry that will contain the PtrList for all processors
+
             PtrList<polyMesh> procMeshes(databases.size());
+            HashTable<PtrList<faMesh>> procAreaRegionMeshes;
+            procAreaRegionMeshes.reserve(areaRegionNames.size());
 
             forAll(databases, proci)
             {
@@ -1408,20 +1416,16 @@ int main(int argc, char *argv[])
                     << "Read processor mesh: "
                     << (databases[proci].caseName()/regionDir) << endl;
 
-                procMeshes.set
+                const polyMesh& procMesh = procMeshes.emplace
                 (
                     proci,
-                    new polyMesh
+                    IOobject
                     (
-                        IOobject
-                        (
-                            regionName,
-                            databases[proci].timeName(),
-                            databases[proci]
-                        )
+                        regionName,
+                        databases[proci].timeName(),
+                        databases[proci]
                     )
                 );
-                const polyMesh& procMesh = procMeshes[proci];
 
                 writeMaps
                 (
@@ -1444,38 +1448,67 @@ int main(int argc, char *argv[])
                             "boundary"
                         );
 
-                    IOobject io
-                    (
-                        "faBoundary",
-                        boundaryInst,
-                        faMesh::meshDir(procMesh, word::null),
-                        procMesh.time(),
-                        IOobject::READ_IF_PRESENT,
-                        IOobject::NO_WRITE,
-                        IOobject::NO_REGISTER
-                    );
-
-                    if (io.typeHeaderOk<faBoundaryMesh>(true))
+                    for (const word& areaName : areaRegionNames)
                     {
-                        // Always based on the volume decomposition!
-                        procFaMeshes.set(proci, new faMesh(procMesh));
+                        IOobject io
+                        (
+                            "faBoundary",
+                            boundaryInst,
+                            faMesh::meshDir(procMesh, areaName),
+                            procMesh.time(),
+                            IOobject::READ_IF_PRESENT,
+                            IOobject::NO_WRITE,
+                            IOobject::NO_REGISTER
+                        );
+
+                        if (io.typeHeaderOk<faBoundaryMesh>(true))
+                        {
+                            // Always based on the volume decomposition!
+                            auto& procFaMeshes = procAreaRegionMeshes(areaName);
+                            procFaMeshes.resize(databases.size());
+
+                            procFaMeshes.set
+                            (
+                                proci,
+                                new faMesh(areaName, procMesh)
+                            );
+                        }
                     }
                 }
             }
 
 
-            // Finite-area mapping
-            doFiniteArea = false;
-            forAll(procFaMeshes, proci)
+            // A finite-area mapping exists if procFaMeshes was filled
+
+            // Re-read reconstructed polyMesh. Note: could probably be avoided
+            // by merging into loops above.
+            refPtr<polyMesh> masterPolyMeshPtr;
+
+            if (!procAreaRegionMeshes.empty())
             {
-                if (procFaMeshes.set(proci))
-                {
-                    doFiniteArea = true;
-                }
+                masterPolyMeshPtr.reset
+                (
+                    new polyMesh
+                    (
+                        IOobject
+                        (
+                            regionName,
+                            runTime.timeName(),
+                            runTime
+                        ),
+                        true
+                    )
+                );
             }
 
-            if (doFiniteArea)
+            // Process any finite-area meshes
+            for (const auto& iter : procAreaRegionMeshes.csorted())
             {
+                const auto& areaName = iter.key();
+                const auto& procFaMeshes = iter.val();
+
+                const polyMesh& masterMesh = masterPolyMeshPtr();
+
                 // Addressing from processor to reconstructed case
                 labelListList faFaceProcAddressing(nProcs);
                 labelListList faEdgeProcAddressing(nProcs);
@@ -1493,32 +1526,10 @@ int main(int argc, char *argv[])
 
                     faBoundProcAddressing[proci] = identity(bm.size());
                     // Mark processor patches
-                    for
-                    (
-                        label patchi = bm.nNonProcessor();
-                        patchi < bm.size();
-                        ++patchi
-                    )
-                    {
-                        faBoundProcAddressing[proci][patchi] = -1;
-                    }
+                    faBoundProcAddressing[proci].slice(bm.nNonProcessor()) = -1;
                 }
 
 
-                // Re-read reconstructed polyMesh. Note: could probably be avoided
-                // by merging into loops above.
-                const polyMesh masterMesh
-                (
-                    IOobject
-                    (
-                        regionName,
-                        runTime.timeName(),
-                        runTime
-                    ),
-                    true
-                );
-
-
                 // faceProcAddressing
                 // ~~~~~~~~~~~~~~~~~~
 
@@ -1553,13 +1564,13 @@ int main(int argc, char *argv[])
                 // Construct without patches
                 faMesh masterFaMesh
                 (
+                    areaName,
                     masterMesh,
                     std::move(masterFaceLabels),
                     io
                 );
 
-                const uindirectPrimitivePatch& masterPatch =
-                    masterFaMesh.patch();
+                const auto& masterPatch = masterFaMesh.patch();
 
 
                 // pointProcAddressing
@@ -1571,7 +1582,7 @@ int main(int argc, char *argv[])
                     const auto& procPatch = procFaMeshes[proci].patch();
                     const auto& mp = procPatch.meshPoints();
 
-                    labelList& pointAddr = faPointProcAddressing[proci];
+                    auto& pointAddr = faPointProcAddressing[proci];
                     pointAddr.resize_nocopy(mp.size());
 
                     forAll(mp, i)
@@ -1620,8 +1631,7 @@ int main(int argc, char *argv[])
                 label nPatches = 0;
                 forAll(completePatches, patchi)
                 {
-                    const labelList& patchEdgeLabels =
-                        singlePatchEdgeLabels[patchi];
+                    const auto& patchEdgeLabels = singlePatchEdgeLabels[patchi];
 
                     const faPatch& fap = procMesh0.boundary()[patchi];
 
@@ -1652,11 +1662,11 @@ int main(int argc, char *argv[])
 
                 // Serial mesh - no parallel communication
 
-                const bool oldParRun = Pstream::parRun(false);
+                const bool oldParRun = UPstream::parRun(false);
 
                 masterFaMesh.addFaPatches(completePatches);
 
-                Pstream::parRun(oldParRun);  // Restore parallel state
+                UPstream::parRun(oldParRun);  // Restore parallel state
 
 
                 // Write mesh & individual addressing

applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.C

@@ -33,99 +33,266 @@ License
 #include "decomposedBlockData.H"
 #include "IFstream.H"
 
-// * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
+// * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
 
-bool Foam::checkFileExistence(const fileName& fName)
+// Trimmed-down version of lookupAndCacheProcessorsPath
+// with Foam::exists() check. No caching.
+
+// Check for two conditions:
+// - file has to exist
+// - if collated the entry has to exist inside the file
+
+// Note: bypass fileOperation::filePath(IOobject&) since has problems
+//       with going to a different number of processors
+//       (in collated format). Use file-based searching instead
+
+namespace Foam
 {
-    // Trimmed-down version of lookupAndCacheProcessorsPath
-    // with Foam::exists() check. No caching.
 
-    // Check for two conditions:
-    // - file has to exist
-    // - if collated the entry has to exist inside the file
-
-    // Note: bypass fileOperation::filePath(IOobject&) since has problems
-    //       with going to a different number of processors
-    //       (in collated format). Use file-based searching instead
-
-    const auto& handler = Foam::fileHandler();
-    typedef fileOperation::procRangeType procRangeType;
-
-    fileName path, pDir, local;
-    procRangeType group;
-    label numProcs;
-    const label proci =
-        fileOperation::splitProcessorPath
-        (fName, path, pDir, local, group, numProcs);
+// If indeed collated format:
+// Collect block-number in individual filenames
+// (might differ on different processors)
+static bool checkFileExistenceCollated
+(
+    const Foam::fileOperation& handler,
+    const Foam::fileName& fName
+)
+{
+    // using namespace Foam;
 
     bool found = false;
-
-    if (proci != -1)
     {
-        // Read all directories to see any beginning with processor
-        // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+        const label handlerComm = handler.comm();
 
-        const fileNameList dirEntries
-        (
-            handler.readDir(path, fileName::Type::DIRECTORY)
-        );
+        const label globalProci = UPstream::myProcNo(UPstream::worldComm);
+        const label handlerProci = UPstream::myProcNo(handlerComm);
+        const label nHandlerProcs = UPstream::nProcs(handlerComm);
 
-        // Extract info from processorN or processorsNN
-        // - highest processor number
-        // - directory+offset containing data for proci
-
-        // label nProcs = 0;
-        for (const fileName& dirN : dirEntries)
+        // Determine my local block number
+        label myBlockNumber = -1;
         {
-            // Analyse directory name
-            label rNum(-1);
-            const label readProci =
-                fileOperation::detectProcessorPath(dirN, group, &rNum);
+            fileOperation::procRangeType group;
+            label proci = fileOperation::detectProcessorPath(fName, group);
 
-            if (proci == readProci)
+            if (proci == -1 && group.empty())
             {
-                // Found "processorN"
-                if (Foam::exists(path/dirN/local))
-                {
-                    found = true;
-                    break;
-                }
+                // 'processorsXXX' format so contains all ranks
+                // according to worldComm
+                myBlockNumber = globalProci;
             }
-            else if (rNum != -1)
+            else
             {
-                // "processorsNN" or "processorsNN_start-end"
-                if (group.empty())
-                {
-                    // "processorsNN"
-                    if (proci < rNum && Foam::exists(path/dirN/local))
-                    {
-                        found = true;
-                        break;
-                    }
-                }
-                else if (group.contains(proci))
-                {
-                    // "processorsNN_start-end"
-                    // - save the local proc offset
-
-                    if (Foam::exists(path/dirN/local))
-                    {
-                        found = true;
-                        break;
-                    }
-                }
+                // 'processorsXXX_n-m' format so check for relative rank
+                myBlockNumber = handlerProci;
             }
         }
-    }
 
-    if (!found)
-    {
-        found = Foam::exists(fName);
+        // Since we are streaming anyhow, could also pack as tuple:
+        // Tuple2<fileName, label>
+
+
+        // Collect file names on master of local communicator
+        const fileNameList fNames
+        (
+            Pstream::listGatherValues
+            (
+                fName,
+                handlerComm,
+                UPstream::msgType()
+            )
+        );
+
+        // Collect block numbers on master of local communicator
+        const labelList myBlockNumbers
+        (
+            Pstream::listGatherValues
+            (
+                myBlockNumber,
+                handlerComm,
+                UPstream::msgType()
+            )
+        );
+
+        // Determine for all whether the filename exists in the collated file.
+        boolList allFound;
+
+        if (UPstream::master(handlerComm))
+        {
+            allFound.resize(nHandlerProcs, false);
+
+            // Store nBlocks and index of file that was used for nBlocks
+            label nBlocks = -1;
+            label blockRanki = -1;
+            forAll(fNames, ranki)
+            {
+                if
+                (
+                    blockRanki == -1
+                 || (fNames[ranki] != fNames[blockRanki])
+                )
+                {
+                    blockRanki = ranki;
+                    IFstream is(fNames[ranki]);
+                    nBlocks = decomposedBlockData::getNumBlocks(is);
+                }
+
+                allFound[ranki] = (myBlockNumbers[ranki] < nBlocks);
+            }
+        }
+
+        // Scatter using the handler communicator
+        found = Pstream::listScatterValues
+        (
+            allFound,
+            handlerComm,
+            UPstream::msgType()
+        );
     }
 
     return found;
 }
 
+} // End namespace
+
+
+// * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
+
+Foam::bitSet Foam::haveProcessorFile
+(
+    const word& name,           // eg "faces"
+    const fileName& instance,   // eg "constant"
+    const fileName& local,      // eg, polyMesh
+    const Time& runTime,
+    const bool verbose
+)
+{
+    const auto& handler = Foam::fileHandler();
+
+    const fileName fName
+    (
+        handler.filePath(runTime.path()/instance/local/name)
+    );
+
+    bool found = handler.isFile(fName);
+
+    // Assume non-collated (as fallback value).
+    // If everyone claims to have the file, use master to verify if
+    // collated is involved.
+
+    bool isCollated = false;
+
+    if (returnReduceAnd(found, UPstream::worldComm))
+    {
+        // Test for collated format.
+        // Note: can test only world-master. Since even host-collated will have
+        // same file format type for all processors
+        if (UPstream::master(UPstream::worldComm))
+        {
+            const bool oldParRun = UPstream::parRun(false);
+
+            if (IFstream is(fName); is.good())
+            {
+                IOobject io(name, instance, local, runTime);
+                io.readHeader(is);
+
+                isCollated = decomposedBlockData::isCollatedType(io);
+            }
+
+            UPstream::parRun(oldParRun);
+        }
+        Pstream::broadcast(isCollated, UPstream::worldComm);
+    }
+
+    // For collated, check that the corresponding blocks exist
+    if (isCollated)
+    {
+        found = checkFileExistenceCollated(handler, fName);
+    }
+
+
+    // Globally consistent information about who has the file
+    bitSet haveFileOnProc = bitSet::allGather(found, UPstream::worldComm);
+
+    if (verbose)
+    {
+        Info<< "Per processor availability of \""
+            << name << "\" file in " << instance/local << nl
+            << "    " << flatOutput(haveFileOnProc) << nl << endl;
+    }
+
+    return haveFileOnProc;
+}
+
+
+Foam::boolList Foam::haveMeshFile
+(
+    const word& name,           // eg "faces"
+    const fileName& instance,   // eg "constant"
+    const fileName& local,      // eg, polyMesh
+    const Time& runTime,
+    const bool verbose
+)
+{
+    const auto& handler = Foam::fileHandler();
+
+    const fileName fName
+    (
+        handler.filePath(runTime.path()/instance/local/name)
+    );
+
+    bool found = handler.isFile(fName);
+
+    // Assume non-collated (as fallback value).
+    // If everyone claims to have the file, use master to verify if
+    // collated is involved.
+
+    bool isCollated = false;
+
+    if (returnReduceAnd(found, UPstream::worldComm))
+    {
+        // Test for collated format.
+        // Note: can test only world-master. Since even host-collated will have
+        // same file format type for all processors
+        if (UPstream::master(UPstream::worldComm))
+        {
+            const bool oldParRun = UPstream::parRun(false);
+
+            if (IFstream is(fName); is.good())
+            {
+                IOobject io(name, instance, local, runTime);
+                io.readHeader(is);
+
+                isCollated = decomposedBlockData::isCollatedType(io);
+            }
+
+            UPstream::parRun(oldParRun);
+        }
+        Pstream::broadcast(isCollated, UPstream::worldComm);
+    }
+
+    // For collated, check that the corresponding blocks exist
+    if (isCollated)
+    {
+        found = checkFileExistenceCollated(handler, fName);
+    }
+
+
+    // Globally consistent information about who has a mesh
+    boolList haveFileOnProc
+    (
+        UPstream::allGatherValues<bool>(found, UPstream::worldComm)
+    );
+
+    if (verbose)
+    {
+        Info<< "Per processor availability of \""
+            << name << "\" file in " << instance/local << nl
+            << "    " << flatOutput(haveFileOnProc) << nl << endl;
+    }
+
+    return haveFileOnProc;
+}
+
 
 Foam::boolList Foam::haveMeshFile
 (
@@ -135,143 +302,49 @@ Foam::boolList Foam::haveMeshFile
     const bool verbose
 )
 {
-    #if 0
-
-    // Simple directory scanning - too fragile
-    bool found = checkFileExistence(runTime.path()/meshPath/meshFile);
-
-    #else
-
-    // Trimmed-down version of lookupAndCacheProcessorsPath
-    // with Foam::exists() check. No caching.
-
-    // Check for two conditions:
-    // - file has to exist
-    // - if collated the entry has to exist inside the file
-
-    // Note: bypass fileOperation::filePath(IOobject&) since has problems
-    //       with going to a different number of processors
-    //       (in collated format). Use file-based searching instead
-
     const auto& handler = Foam::fileHandler();
-    typedef fileOperation::procRangeType procRangeType;
 
     const fileName fName
     (
         handler.filePath(runTime.path()/meshPath/meshFile)
     );
+
     bool found = handler.isFile(fName);
-    if (returnReduceAnd(found)) // worldComm
+
+    // Assume non-collated (as fallback value).
+    // If everyone claims to have the file, use master to verify if
+    // collated is involved.
+
+    bool isCollated = false;
+
+    if (returnReduceAnd(found, UPstream::worldComm))
     {
-        // Bit tricky: avoid having all slaves open file since this involves
-        // reading it on master and broadcasting it. This fails if file > 2G.
-        // So instead only read on master
-
-        bool isCollated = false;
-
+        // Test for collated format.
         // Note: can test only world-master. Since even host-collated will have
         // same file format type for all processors
         if (UPstream::master(UPstream::worldComm))
         {
             const bool oldParRun = UPstream::parRun(false);
 
-            IFstream is(fName);
-            if (is.good())
+            if (IFstream is(fName); is.good())
             {
                 IOobject io(meshFile, meshPath, runTime);
                 io.readHeader(is);
 
                 isCollated = decomposedBlockData::isCollatedType(io);
             }
+
             UPstream::parRun(oldParRun);
         }
-        Pstream::broadcast(isCollated); //UPstream::worldComm
-
-
-        // Collect block-number in individual filenames (might differ
-        // on different processors)
-        if (isCollated)
-        {
-            const label nProcs = UPstream::nProcs(fileHandler().comm());
-            const label myProcNo = UPstream::myProcNo(fileHandler().comm());
-
-            // Collect file names on master of local communicator
-            const fileNameList fNames
-            (
-                Pstream::listGatherValues
-                (
-                    fName,
-                    fileHandler().comm(),
-                    UPstream::msgType()
-                )
-            );
-
-            // Collect local block number
-            label myBlockNumber = -1;
-            {
-                procRangeType group;
-                label proci = fileOperation::detectProcessorPath(fName, group);
-
-                if (proci == -1 && group.empty())
-                {
-                    // 'processorsXXX' format so contains all ranks
-                    // according to worldComm
-                    myBlockNumber = UPstream::myProcNo(UPstream::worldComm);
-                }
-                else
-                {
-                    // 'processorsXXX_n-m' format so check for the
-                    // relative rank
-                    myBlockNumber = myProcNo;
-                }
-            }
-            const labelList myBlockNumbers
-            (
-                Pstream::listGatherValues
-                (
-                    myBlockNumber,
-                    fileHandler().comm(),
-                    UPstream::msgType()
-                )
-            );
-
-
-
-            // Determine for all whether the filename exists in the collated
-            // file.
-            boolList allFound(nProcs, false);
-
-            if (UPstream::master(fileHandler().comm()))
-            {
-                // Store nBlocks and index of file that was used for nBlocks
-                label nBlocks = -1;
-                label blockRanki = -1;
-                forAll(fNames, ranki)
-                {
-                    if
-                    (
-                        blockRanki == -1
-                     || (fNames[ranki] != fNames[blockRanki])
-                    )
-                    {
-                        blockRanki = ranki;
-                        IFstream is(fNames[ranki]);
-                        nBlocks = decomposedBlockData::getNumBlocks(is);
-                    }
-
-                    allFound[ranki] = (myBlockNumbers[ranki] < nBlocks);
-                }
-            }
-
-            found = Pstream::listScatterValues
-            (
-                allFound,
-                fileHandler().comm(),
-                UPstream::msgType()
-            );
-        }
+        Pstream::broadcast(isCollated, UPstream::worldComm);
     }
-    #endif
+
+    // For collated, check that the corresponding blocks exist
+    if (isCollated)
+    {
+        found = checkFileExistenceCollated(handler, fName);
+    }
+
 
     // Globally consistent information about who has a mesh
     boolList haveFileOnProc

applications/utilities/parallelProcessing/redistributePar/loadOrCreateMesh.H

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012 OpenFOAM Foundation
-    Copyright (C) 2022-2023 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,15 +48,32 @@ namespace Foam
 // Forward Declarations
 class faMesh;
 
-//- Check for availability of given file
-bool checkFileExistence(const fileName& fName);
+//- Check for availability of specified file (on all ranks)
+bitSet haveProcessorFile
+(
+    const word& name,           // eg, "faces"
+    const fileName& instance,   // eg, "constant"
+    const fileName& local,      // eg, "polyMesh"
+    const Time& runTime,
+    const bool verbose = true
+);
 
-//- Check for availability of specified mesh file (default: "faces")
+//- Check for availability of specified file (on all ranks)
+boolList haveMeshFile
+(
+    const word& name,           // eg, "faces"
+    const fileName& instance,   // eg, "constant"
+    const fileName& local,      // eg, "polyMesh"
+    const Time& runTime,
+    const bool verbose = true
+);
+
+//- Check for availability of specified mesh file
 boolList haveMeshFile
 (
     const Time& runTime,
     const fileName& meshPath,
-    const word& meshFile = "faces",
+    const word& meshFile,
     const bool verbose = true
 );
 
@@ -75,7 +92,7 @@ void masterMeshInstance
     fileName& pointsInstance
 );
 
-}
+} // End namespace Foam
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 

applications/utilities/postProcessing/dataConversion/foamToEnsight/checkFieldAvailability.H

@@ -21,44 +21,59 @@ Requires
 
 // Initially all possible objects that are available at the final time
 List<wordHashSet> availableRegionObjectNames(meshes.size());
-List<wordHashSet> availableFaRegionObjectNames(meshes.size());
+List<HashTable<wordHashSet>> availableFaRegionObjectNames(meshes.size());
 
 forAll(meshes, regioni)
 {
     const auto& mesh = meshes[regioni];
 
     IOobjectList objects;
-    IOobjectList faObjects;
+    HashTable<IOobjectList> faObjects;
 
     if (doConvertFields && !timeDirs.empty())
     {
+        // const word& checkTimeDir = timeDirs.back().name();
+
         // List of volume mesh objects for this instance
         objects = IOobjectList(mesh, timeDirs.back().name());
 
-        // List of area mesh objects (assuming single region)
-        faObjects = IOobjectList
-        (
-            mesh.time(),
-            timeDirs.back().name(),
-            faMesh::dbDir(mesh, word::null),
-            IOobjectOption::NO_REGISTER
-        );
-
         if (fieldSelector)
         {
             objects.filterObjects(fieldSelector);
-            faObjects.filterObjects(fieldSelector);
         }
 
         // Remove "*_0" restart fields
         objects.prune_0();
-        faObjects.prune_0();
 
         if (!doPointValues)
         {
             // Prune point fields if disabled
             objects.filterClasses(Foam::fieldTypes::is_point, true);
         }
+
+
+        // The finite-area regions and their fields for this volume region
+        // and instance
+        faObjects.reserve(areaRegionNames.size());
+        for (const word& areaName : areaRegionNames)
+        {
+            IOobjectList objs
+            (
+                faMesh::Registry(mesh),
+                timeDirs.back().name(),
+                polyMesh::regionName(areaName),
+                IOobjectOption::NO_REGISTER
+            );
+
+            if (fieldSelector)
+            {
+                objs.filterObjects(fieldSelector);
+            }
+
+            // Remove "*_0" restart fields
+            objs.prune_0();
+            faObjects(areaName) = std::move(objs);
+        }
     }
 
     // Volume fields
@@ -78,20 +93,29 @@ forAll(meshes, regioni)
     }
 
     // Area fields
-    if (!faObjects.empty())
+    for (const word& areaName : areaRegionNames)
     {
-        wordList objectNames(faObjects.sortedNames());
+        wordList objectNames;
 
-        // Check availability for all times... (assuming single region)
-        checkData
+        if (const auto iter = faObjects.cfind(areaName); iter.good())
+        {
+            objectNames = iter.val().sortedNames();
+
+            // Check availability for all times...
+            checkData
+            (
+                faMesh::Registry(mesh),
+                timeDirs,
+                objectNames,
+                polyMesh::regionName(areaName)
+            );
+        }
+
+        availableFaRegionObjectNames[regioni].emplace_set
         (
-            mesh.time(),
-            timeDirs,
-            objectNames,
-            faMesh::dbDir(mesh, word::null)
+            areaName,
+            std::move(objectNames)
         );
-
-        availableFaRegionObjectNames[regioni] = objectNames;
     }
 }
 

applications/utilities/postProcessing/dataConversion/foamToEnsight/createMeshAccounting.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021-2022 OpenCFD Ltd.
+    Copyright (C) 2021-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -15,12 +15,14 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
+// Cases and meshes per volume region
 PtrList<ensightCase> ensightCases(regionNames.size());
 PtrList<ensightMesh> ensightMeshes(regionNames.size());
 
-PtrList<faMesh> meshesFa(regionNames.size());
-PtrList<ensightCase> ensightCasesFa(regionNames.size());
-PtrList<ensightFaMesh> ensightMeshesFa(regionNames.size());
+// Per volume region can have multiple finite-area regions
+List<PtrDynList<faMesh>> meshesFa(regionNames.size());
+List<PtrDynList<ensightCase>> ensightCasesFa(regionNames.size());
+List<PtrDynList<ensightFaMesh>> ensightMeshesFa(regionNames.size());
 
 {
     forAll(regionNames, regioni)
@@ -45,6 +47,7 @@ PtrList<ensightFaMesh> ensightMeshesFa(regionNames.size());
             }
         }
 
+        // Volume mesh
         ensightMeshes.set
         (
             regioni,
@@ -59,33 +62,60 @@ PtrList<ensightFaMesh> ensightMeshesFa(regionNames.size());
             new ensightCase(ensCasePath, ensCaseName, caseOpts)
         );
 
-        if (doFiniteArea)
+        if (!doFiniteArea)
         {
-            autoPtr<faMesh> faMeshPtr(faMesh::TryNew(mesh));
+            continue;
+        }
+
+        // Note: not every volume region is guaranteed to have
+        // any or all area region(s)
+
+        meshesFa[regioni].reserve_exact(areaRegionNames.size());
+
+        for (const word& areaName : areaRegionNames)
+        {
+            auto faMeshPtr = faMesh::TryNew(areaName, mesh);
 
             if (faMeshPtr)
             {
-                ensightCasesFa.set
-                (
-                    regioni,
-                    new ensightCase
-                    (
-                        ensCasePath/"finite-area",
-                        "finite-area",
-                        caseOpts
-                    )
-                );
-
-                meshesFa.set(regioni, std::move(faMeshPtr));
-
-                ensightMeshesFa.set
-                (
-                    regioni,
-                    new ensightFaMesh(meshesFa[regioni])
-                );
-                ensightMeshesFa[regioni].verbose(optVerbose);
+                meshesFa[regioni].push_back(std::move(faMeshPtr));
             }
         }
+
+        // Setup the ensight components
+        const label nAreas = meshesFa[regioni].size();
+        ensightCasesFa[regioni].reserve_exact(nAreas);
+        ensightMeshesFa[regioni].reserve_exact(nAreas);
+
+        for (const faMesh& areaMesh : meshesFa[regioni])
+        {
+            // Use regionName() - automatically filters for defaultRegion
+            const word& areaName = areaMesh.regionName();
+
+            if (areaName.empty())
+            {
+                // single-region
+                ensightCasesFa[regioni].emplace_back
+                (
+                    ensCasePath/"finite-area",
+                    "finite-area",
+                    caseOpts
+                );
+            }
+            else
+            {
+                // multi-region
+                ensightCasesFa[regioni].emplace_back
+                (
+                    ensCasePath/"finite-area"/areaName,
+                    areaName,
+                    caseOpts
+                );
+            }
+
+            auto& ensFaMesh = ensightMeshesFa[regioni].emplace_back(areaMesh);
+            ensFaMesh.verbose(optVerbose);
+        }
     }
 }
 

applications/utilities/postProcessing/dataConversion/foamToEnsight/foamToEnsight.C

@@ -124,6 +124,7 @@ Usage
 #include "OFstream.H"
 #include "Pstream.H"
 #include "HashOps.H"
+#include "PtrDynList.H"
 #include "regionProperties.H"
 
 #include "fvc.H"
@@ -172,6 +173,7 @@ int main(int argc, char *argv[])
     argList::addVerboseOption();
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
 
     argList::addBoolOption
     (
@@ -323,6 +325,9 @@ int main(int argc, char *argv[])
     );
     argList::addOptionCompat("cellZones", {"cellZone", 1912});
 
+    // Prevent volume BCs from triggering finite-area
+    regionModels::allowFaModels(false);
+
     #include "setRootCase.H"
 
     // ------------------------------------------------------------------------
@@ -436,6 +441,14 @@ int main(int argc, char *argv[])
     // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
     // ------------------------------------------------------------------------
     // Directory management
 
@@ -515,29 +528,32 @@ int main(int argc, char *argv[])
             polyMesh::readUpdateState meshState = mesh.readUpdate();
             const bool moving = (meshState != polyMesh::UNCHANGED);
 
-            // Ensight
+            // Ensight (fvMesh)
             auto& ensCase = ensightCases[regioni];
             auto& ensMesh = ensightMeshes[regioni];
 
-            // Finite-area (can be missing)
-            auto* ensFaCasePtr = ensightCasesFa.get(regioni);
-            auto* ensFaMeshPtr = ensightMeshesFa.get(regioni);
-
             ensCase.setTime(timeDirs[timei], timeIndex);
-            if (ensFaCasePtr)
+
+            // Finite-area (optional)
+            // Accounting exists for each volume region but may be empty
+            auto& ensFaCases = ensightCasesFa[regioni];
+            auto& ensFaMeshes = ensightMeshesFa[regioni];
+
+            for (auto& ensFaCase : ensFaCases)
             {
-                ensFaCasePtr->setTime(timeDirs[timei], timeIndex);
+                ensFaCase.setTime(timeDirs[timei], timeIndex);
             }
 
+            // Movement
             if (moving)
             {
                 ensMesh.expire();
                 ensMesh.correct();
 
-                if (ensFaMeshPtr)
+                for (auto& ensFaMesh : ensFaMeshes)
                 {
-                    ensFaMeshPtr->expire();
-                    ensFaMeshPtr->correct();
+                    ensFaMesh.expire();
+                    ensFaMesh.correct();
                 }
             }
 
@@ -552,15 +568,19 @@ int main(int argc, char *argv[])
                 }
 
                 // finite-area
-                if (ensFaCasePtr && ensFaMeshPtr)
+                forAll(ensFaMeshes, areai)
                 {
-                    autoPtr<ensightGeoFile> os =
-                        ensFaCasePtr->newGeometry(hasMovingMesh);
+                    const auto& ensFaCase = ensFaCases[areai];
+                    const auto& ensFaMesh = ensFaMeshes[areai];
 
-                    ensFaMeshPtr->write(os.ref());
+                    autoPtr<ensightGeoFile> os =
+                        ensFaCase.newGeometry(hasMovingMesh);
+
+                    ensFaMesh.write(os.ref());
                 }
             }
 
+
             // Objects at this time
             IOobjectList objects(mesh, runTime.timeName());
 
@@ -572,23 +592,37 @@ int main(int argc, char *argv[])
             // Volume, internal, point fields
             #include "convertVolumeFields.H"
 
-            // The finite-area objects at this time
-            IOobjectList faObjects;
-
-            if (ensFaMeshPtr)
+            // finite-area
+            forAll(ensFaMeshes, areai)
             {
-                faObjects =
-                    IOobjectList(ensFaMeshPtr->mesh(), runTime.timeName());
+                auto* ensFaCasePtr = ensFaCases.get(areai);
+                auto* ensFaMeshPtr = ensFaMeshes.get(areai);
 
-                faObjects.filterObjects
-                (
-                    availableFaRegionObjectNames[regioni]
-                );
+                // The finite-area region objects at this time
+                IOobjectList faObjects;
+
+                if (ensFaMeshPtr)
+                {
+                    const word& areaName = ensFaMeshPtr->mesh().name();
+
+                    faObjects = IOobjectList
+                    (
+                        faMesh::Registry(mesh),
+                        runTime.timeName(),
+                        polyMesh::regionName(areaName),
+                        IOobjectOption::NO_REGISTER
+                    );
+
+                    faObjects.filterObjects
+                    (
+                        availableFaRegionObjectNames[regioni](areaName)
+                    );
+                }
+
+                // The finiteArea fields
+                #include "convertAreaFields.H"
             }
 
-            // The finiteArea fields
-            #include "convertAreaFields.H"
-
             // Lagrangian fields
             #include "convertLagrangian.H"
         }
@@ -601,14 +635,13 @@ int main(int argc, char *argv[])
     // Write cases
     forAll(ensightCases, regioni)
     {
+        // finite-volume
         ensightCases[regioni].write();
-    }
 
-    forAll(ensightCasesFa, regioni)
-    {
-        if (ensightCasesFa.set(regioni))
+        // Finite-area (if any)
+        for (const auto& ensFaCase : ensightCasesFa[regioni])
         {
-            ensightCasesFa[regioni].write();
+            ensFaCase.write();
         }
     }
 

applications/utilities/postProcessing/dataConversion/foamToEnsight/readFields.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2023 OpenCFD Ltd.
+    Copyright (C) 2018-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -26,7 +26,6 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "readFields.H"
-#include "volFields.H"
 
 // * * * * * * * * * * * * * * * Global Functions  * * * * * * * * * * * * * //
 
@@ -42,26 +41,30 @@ Foam::label Foam::checkData
 
     wordHashSet goodFields;
 
+    IOobject io
+    (
+        "any-name",   // placeholder
+        "constant",   // placeholder
+        local,
+        obr,
+        IOobjectOption::NO_READ,
+        IOobjectOption::NO_WRITE,
+        IOobjectOption::NO_REGISTER
+    );
+
     for (const word& fieldName : objectNames)
     {
-        // // If prune_0() not previously used...
-        // if (objectNames.ends_with("_0")) continue;
+        // In case prune_0() not previously used...
+        if (fieldName.ends_with("_0")) continue;
 
         bool good = false;
 
         for (const instant& inst : timeDirs)
         {
-            good =
-                IOobject
-                (
-                    fieldName,
-                    inst.name(),
-                    local,
-                    obr,
-                    IOobject::NO_READ,
-                    IOobject::NO_WRITE,
-                    IOobject::NO_REGISTER
-                ).typeHeaderOk<volScalarField>(false, false);
+            io.resetHeader(fieldName);
+            io.instance() = inst.name();
+
+            good = io.typeHeaderOk<regIOobject>(false, false);
 
             if (!good)
             {

applications/utilities/postProcessing/dataConversion/foamToVTK/convertAreaFields.H

@@ -22,24 +22,66 @@ Description
 //
 
 // No subsetting!
-if (doFiniteArea)
+if (doFiniteArea && !areaRegionNames.empty())
 {
     using reportFields = foamToVtkReportFields;
 
-    autoPtr<faMesh> faMeshPtr;
+    // The (region) polyMesh being used. No subsetting possible
+    const auto& basePolyMesh = meshProxy.baseMesh();
 
-    const label nAreaFields = faObjects.count(Foam::fieldTypes::is_area);
-
-    if (nAreaFields || withMeshIds)
+    for (const word& areaName : areaRegionNames)
     {
-        faMeshPtr = faMesh::TryNew(meshProxy.baseMesh());
-    }
+        const bool isDefaultRegion(polyMesh::regionName(areaName).empty());
 
-    if (faMeshPtr && (nAreaFields || withMeshIds))
-    {
-        const faMesh& areaMesh = faMeshPtr();
+        // CAUTION
+        // If we want to have constant access to the HashTable:
+        //
+        // (SEGFAULT)
+        // const auto& faObjs = faObjects.lookup(areaName, IOobjectList());
+        //
+        // Use an empty fallback to avoid binding to a temporary:
+        //
+        // const IOobjectList emptyObjectList;
+        // const auto& faObjs = faObjects.lookup(areaName, emptyObjectList);
 
-        reportFields::area(Info, faObjects);
+        // Since we do not need the area fields afterwards,
+        // just move them out from the HashTable
+
+        IOobjectList faObjs;
+        if (auto iter = faObjects.find(areaName); iter.good())
+        {
+            faObjs = std::move(iter.val());
+        }
+
+        const label nAreaFields = faObjs.count(Foam::fieldTypes::is_area);
+
+        autoPtr<faMesh> faMeshPtr;
+
+        if (nAreaFields || withMeshIds)
+        {
+            faMeshPtr = faMesh::TryNew(areaName, basePolyMesh);
+        }
+
+        if (!faMeshPtr)
+        {
+            if (!isDefaultRegion)
+            {
+                // Report any area region specified but missing
+                // - silently ignore region0
+                Info<< "No area-mesh [" << polyMesh::regionName(areaName)
+                    << "] on volume-region ["
+                    << basePolyMesh.regionName() << "]" << endl;
+            }
+            continue;
+        }
+        const auto& areaMesh = faMeshPtr();
+
+        Info<< "Using area-mesh [" << polyMesh::regionName(areaName)
+            << "] on volume-region ["
+            << basePolyMesh.regionName() << "]" << endl;
+
+
+        reportFields::area(Info, faObjs);
 
         const auto& pp = faMeshPtr->patch();
 
@@ -49,7 +91,12 @@ if (doFiniteArea)
             writeOpts,
             (
                 outputDir/regionDir/"finite-area"
-              / "finiteArea" + timeDesc
+              / (
+                   isDefaultRegion
+                 ? fileName("finiteArea")
+                 : fileName(areaName/areaName)
+                )
+              + timeDesc
             ),
             UPstream::parRun()
         );
@@ -96,7 +143,7 @@ if (doFiniteArea)
         (
             writer,
             areaMesh,
-            faObjects,
+            faObjs,
             true // syncPar
         );
 

applications/utilities/postProcessing/dataConversion/foamToVTK/foamToVTK.C

@@ -135,13 +135,13 @@ Note
 #include "emptyPolyPatch.H"
 #include "volPointInterpolation.H"
 #include "faceZoneMesh.H"
+#include "faMesh.H"
 #include "areaFields.H"
 #include "fvMeshSubsetProxy.H"
 #include "faceSet.H"
 #include "pointSet.H"
 #include "HashOps.H"
 #include "regionProperties.H"
-#include "stringListOps.H"  // For stringListOps::findMatching()
 
 #include "Cloud.H"
 #include "readFields.H"
@@ -434,6 +434,7 @@ int main(int argc, char *argv[])
     argList::addOptionCompat("one-boundary", {"allPatches", 1806});
 
     #include "addAllRegionOptions.H"
+    #include "addAllFaRegionOptions.H"
 
     argList::addOption
     (
@@ -479,8 +480,14 @@ int main(int argc, char *argv[])
         "Directory name for VTK output (default: 'VTK')"
     );
 
+    // Prevent volume BCs from triggering finite-area
+    regionModels::allowFaModels(false);
+
     #include "setRootCase.H"
 
+    // ------------------------------------------------------------------------
+    // Configuration
+
     /// const int optVerbose = args.verbose();
     const bool decomposePoly = args.found("poly-decomp");
     const bool doBoundary    = !args.found("no-boundary");
@@ -624,6 +631,16 @@ int main(int argc, char *argv[])
     // Handle -allRegions, -regions, -region
     #include "getAllRegionOptions.H"
 
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
+
+    if (!doFiniteArea)
+    {
+        areaRegionNames.clear();  // For consistency
+    }
+
+    // ------------------------------------------------------------------------
+
     // Names for sets and zones
     word cellSelectionName;
     word faceSetName;
@@ -771,8 +788,11 @@ int main(int argc, char *argv[])
                 }
             }
 
+            // fvMesh fields
             IOobjectList objects;
-            IOobjectList faObjects;
+
+            // faMesh fields (multiple finite-area regions per volume region)
+            HashTable<IOobjectList> faObjects;
 
             if (doConvertFields)
             {
@@ -780,33 +800,51 @@ int main(int argc, char *argv[])
                 objects =
                     IOobjectList(meshProxy.baseMesh(), runTime.timeName());
 
-                // List of area mesh objects (assuming single region)
-                faObjects =
-                    IOobjectList
-                    (
-                        runTime,
-                        runTime.timeName(),
-                        faMesh::dbDir(meshProxy.baseMesh(), word::null),
-                        IOobjectOption::NO_REGISTER
-                    );
-
                 if (fieldSelector)
                 {
                     objects.filterObjects(fieldSelector);
-                    faObjects.filterObjects(fieldSelector);
                 }
-
                 // Remove "*_0" restart fields
                 objects.prune_0();
-                faObjects.prune_0();
 
                 if (!doPointValues)
                 {
                     // Prune point fields if disabled
                     objects.filterClasses(Foam::fieldTypes::is_point, true);
                 }
+
+
+                // Lists of finite-area fields
+                faObjects.reserve(areaRegionNames.size());
+
+                for (const word& areaName : areaRegionNames)
+                {
+                    // The finite-area objects for given area region.
+                    // Add as method to faMeshesRegistry?
+
+                    IOobjectList objs
+                    (
+                        faMesh::Registry(meshProxy.baseMesh()),
+                        runTime.timeName(),
+                        polyMesh::regionName(areaName),
+                        IOobjectOption::NO_REGISTER
+                    );
+
+                    if (fieldSelector)
+                    {
+                        objs.filterObjects(fieldSelector);
+                    }
+                    // Remove "*_0" restart fields
+                    objs.prune_0();
+
+                    if (!objs.empty())
+                    {
+                        faObjects.emplace_set(areaName, std::move(objs));
+                    }
+                }
             }
 
+
             if (processorFieldsOnly)
             {
                 // Processor-patches only and continue

applications/utilities/preProcessing/setFields/Make/options

@@ -1,10 +1,10 @@
 EXE_INC = \
+    -I$(LIB_SRC)/meshTools/lnInclude \
     -I$(LIB_SRC)/finiteVolume/lnInclude \
-    -I$(LIB_SRC)/finiteArea/lnInclude \
-    -I$(LIB_SRC)/meshTools/lnInclude
+    -I$(LIB_SRC)/finiteArea/lnInclude
 
 EXE_LIBS = \
+    -lmeshTools \
     -lfiniteVolume \
     -lfiniteArea \
-    -lmeshTools \
     -lgenericPatchFields

applications/utilities/preProcessing/setFields/setFields.C

@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2022-2024 OpenCFD Ltd.
+    Copyright (C) 2022-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -47,6 +47,7 @@ Description
 #include "areaFields.H"
 #include "coupledFvPatch.H"
 #include "coupledFaPatch.H"
+#include "regionProperties.H"
 
 using namespace Foam;
 
@@ -86,17 +87,18 @@ bool consumeUnusedType(const fieldDescription& fieldDesc, Istream& is)
     //? typedef GeometricField<Type, faePatchField, areaMesh> fieldType3;
     //? typedef GeometricField<Type, fvsPatchField, volMesh>  fieldType4;
 
-    if
+    const bool isExpectedType
     (
         fieldDesc.type() == fieldType1::typeName
      || fieldDesc.type() == fieldType2::typeName
-    )
+    );
+
+    if (isExpectedType)
     {
         (void) pTraits<Type>(is);
-        return true;
     }
 
-    return false;
+    return isExpectedType;
 }
 
 
@@ -122,13 +124,18 @@ bool setCellFieldType
 (
     const fieldDescription& fieldDesc,
     const fvMesh& mesh,
-    const labelList& selectedCells,
+    const labelUList& selectedCells,
     Istream& is
 )
 {
     typedef GeometricField<Type, fvPatchField, volMesh> fieldType;
 
-    if (fieldDesc.type() != fieldType::typeName)
+    const bool isExpectedType
+    (
+        fieldDesc.type() == fieldType::typeName
+    );
+
+    if (!isExpectedType)
     {
         return false;
     }
@@ -143,7 +150,9 @@ bool setCellFieldType
         fieldDesc.name(),
         mesh.thisDb().time().timeName(),
         mesh.thisDb(),
-        IOobject::MUST_READ
+        IOobjectOption::MUST_READ,
+        IOobjectOption::NO_WRITE,
+        IOobjectOption::NO_REGISTER
     );
 
     bool found = fieldHeader.typeHeaderOk<fieldType>(true);
@@ -151,13 +160,8 @@ bool setCellFieldType
     if (!found)
     {
         // Fallback to "constant" directory
-        fieldHeader = IOobject
-        (
-            fieldDesc.name(),
-            mesh.thisDb().time().constant(),
-            mesh.thisDb(),
-            IOobject::MUST_READ
-        );
+        fieldHeader.resetHeader();
+        fieldHeader.instance() = mesh.thisDb().time().constant();
         found = fieldHeader.typeHeaderOk<fieldType>(true);
     }
 
@@ -171,7 +175,7 @@ bool setCellFieldType
 
         fieldType field(fieldHeader, mesh, false);
 
-        if (isNull(selectedCells) || selectedCells.size() == field.size())
+        if (isNull(selectedCells) || (selectedCells.size() == field.size()))
         {
             field.primitiveFieldRef() = fieldValue;
         }
@@ -204,7 +208,7 @@ bool setCellFieldType
             << "Field " << fieldDesc.name() << " not found" << endl;
     }
 
-    return true;
+    return isExpectedType;
 }
 
 
@@ -216,13 +220,18 @@ bool setAreaFieldType
 (
     const fieldDescription& fieldDesc,
     const faMesh& mesh,
-    const labelList& selectedFaces,
+    const labelUList& selectedFaces,
     Istream& is
 )
 {
     typedef GeometricField<Type, faPatchField, areaMesh> fieldType;
 
-    if (fieldDesc.type() != fieldType::typeName)
+    const bool isExpectedType
+    (
+        fieldDesc.type() == fieldType::typeName
+    );
+
+    if (!isExpectedType)
     {
         return false;
     }
@@ -237,7 +246,9 @@ bool setAreaFieldType
         fieldDesc.name(),
         mesh.thisDb().time().timeName(),
         mesh.thisDb(),
-        IOobject::MUST_READ
+        IOobjectOption::MUST_READ,
+        IOobjectOption::NO_WRITE,
+        IOobjectOption::NO_REGISTER
     );
 
     bool found = fieldHeader.typeHeaderOk<fieldType>(true);
@@ -245,13 +256,8 @@ bool setAreaFieldType
     if (!found)
     {
         // Fallback to "constant" directory
-        fieldHeader = IOobject
-        (
-            fieldDesc.name(),
-            mesh.thisDb().time().constant(),
-            mesh.thisDb(),
-            IOobject::MUST_READ
-        );
+        fieldHeader.resetHeader();
+        fieldHeader.instance() = mesh.thisDb().time().constant(),
         found = fieldHeader.typeHeaderOk<fieldType>(true);
     }
 
@@ -292,7 +298,7 @@ bool setAreaFieldType
             << "Field " << fieldDesc.name() << " not found" << endl;
     }
 
-    return true;
+    return isExpectedType;
 }
 
 
@@ -304,13 +310,18 @@ bool setFaceFieldType
 (
     const fieldDescription& fieldDesc,
     const fvMesh& mesh,
-    const labelList& selectedFaces,
+    const labelUList& selectedFaces,
     Istream& is
 )
 {
     typedef GeometricField<Type, fvPatchField, volMesh> fieldType;
 
-    if (fieldDesc.type() != fieldType::typeName)
+    const bool isExpectedType
+    (
+        fieldDesc.type() == fieldType::typeName
+    );
+
+    if (!isExpectedType)
     {
         return false;
     }
@@ -325,7 +336,9 @@ bool setFaceFieldType
         fieldDesc.name(),
         mesh.thisDb().time().timeName(),
         mesh.thisDb(),
-        IOobject::MUST_READ
+        IOobjectOption::MUST_READ,
+        IOobjectOption::NO_WRITE,
+        IOobjectOption::NO_REGISTER
     );
 
     bool found = fieldHeader.typeHeaderOk<fieldType>(true);
@@ -333,13 +346,8 @@ bool setFaceFieldType
     if (!found)
     {
         // Fallback to "constant" directory
-        fieldHeader = IOobject
-        (
-            fieldDesc.name(),
-            mesh.thisDb().time().constant(),
-            mesh.thisDb(),
-            IOobject::MUST_READ
-        );
+        fieldHeader.resetHeader();
+        fieldHeader.instance() = mesh.thisDb().time().constant();
         found = fieldHeader.typeHeaderOk<fieldType>(true);
     }
 
@@ -355,15 +363,14 @@ bool setFaceFieldType
 
         // Create flat list of selected faces and their value.
         Field<Type> allBoundaryValues(mesh.nBoundaryFaces());
-        forAll(field.boundaryField(), patchi)
+        for (const auto& pfld : field.boundaryField())
         {
             SubField<Type>
             (
                 allBoundaryValues,
-                field.boundaryField()[patchi].size(),
-                field.boundaryField()[patchi].patch().start()
-              - mesh.nInternalFaces()
-            ) = field.boundaryField()[patchi];
+                pfld.size(),
+                pfld.patch().offset()
+            ) = pfld;
         }
 
         // Override
@@ -424,8 +431,7 @@ bool setFaceFieldType
                 (
                     allBoundaryValues,
                     fieldBf[patchi].size(),
-                    fieldBf[patchi].patch().start()
-                  - mesh.nInternalFaces()
+                    fieldBf[patchi].patch().offset()
                 );
             }
         }
@@ -445,7 +451,7 @@ bool setFaceFieldType
             << "Field " << fieldDesc.name() << " not found" << endl;
     }
 
-    return true;
+    return isExpectedType;
 }
 
 
@@ -460,7 +466,7 @@ struct setCellField
     (
         const fieldDescription& fieldDesc,
         const fvMesh& m,
-        const labelList& selectedCells,
+        const labelUList& selectedCells,
         Istream& is
     )
     {
@@ -477,11 +483,11 @@ struct setCellField
     class iNew
     {
         const fvMesh& mesh_;
-        const labelList& selected_;
+        const labelUList& selected_;
 
     public:
 
-        iNew(const fvMesh& mesh, const labelList& selectedCells)
+        iNew(const fvMesh& mesh, const labelUList& selectedCells) noexcept
         :
             mesh_(mesh),
             selected_(selectedCells)
@@ -528,7 +534,7 @@ struct setFaceField
     (
         const fieldDescription& fieldDesc,
         const fvMesh& m,
-        const labelList& selectedFaces,
+        const labelUList& selectedFaces,
         Istream& is
     )
     {
@@ -545,11 +551,11 @@ struct setFaceField
     class iNew
     {
         const fvMesh& mesh_;
-        const labelList& selected_;
+        const labelUList& selected_;
 
     public:
 
-        iNew(const fvMesh& mesh, const labelList& selectedFaces)
+        iNew(const fvMesh& mesh, const labelUList& selectedFaces) noexcept
         :
             mesh_(mesh),
             selected_(selectedFaces)
@@ -596,7 +602,7 @@ struct setAreaField
     (
         const fieldDescription& fieldDesc,
         const faMesh& m,
-        const labelList& selectedFaces,
+        const labelUList& selectedFaces,
         Istream& is
     )
     {
@@ -613,11 +619,11 @@ struct setAreaField
     class iNew
     {
         const faMesh& mesh_;
-        const labelList& selected_;
+        const labelUList& selected_;
 
     public:
 
-        iNew(const faMesh& mesh, const labelList& selectedFaces)
+        iNew(const faMesh& mesh, const labelUList& selectedFaces) noexcept
         :
             mesh_(mesh),
             selected_(selectedFaces)
@@ -675,6 +681,7 @@ int main(int argc, char *argv[])
     );
 
     #include "addRegionOption.H"
+    #include "addAllFaRegionOptions.H"
 
     // -------------------------
 
@@ -686,15 +693,59 @@ int main(int argc, char *argv[])
 
     #include "createNamedMesh.H"
 
-    autoPtr<faMesh> faMeshPtr;
+    // Handle -all-area-regions, -area-regions, -area-region
+    #include "getAllFaRegionOptions.H"
 
-    if (!args.found("no-finite-area"))
+    if (args.found("no-finite-area"))
     {
-        faMeshPtr = faMesh::TryNew(mesh);
+        areaRegionNames.clear();  // For consistency
     }
-    if (faMeshPtr)
+
+    // ------------------------------------------------------------------------
+
+    PtrList<faMesh> faMeshes;
+
+    // Setup all area meshes on this region
+    if (!areaRegionNames.empty())  // ie, !args.found("no-finite-area")
     {
-        Info<< "Detected finite-area mesh" << nl;
+        faMeshes.resize(areaRegionNames.size());
+
+        label nGoodRegions(0);
+
+        for (const word& areaName : areaRegionNames)
+        {
+            autoPtr<faMesh> faMeshPtr = faMesh::TryNew(areaName, mesh);
+
+            if (faMeshPtr)
+            {
+                faMeshes.set(nGoodRegions++, std::move(faMeshPtr));
+            }
+        }
+
+        faMeshes.resize(nGoodRegions);
+    }
+
+    if (faMeshes.size() == 1)
+    {
+        Info<< "Using finite-area mesh";
+        if
+        (
+            const word& name = polyMesh::regionName(faMeshes[0].name());
+            !name.empty()
+        )
+        {
+            Info<< " [" << name << "]";
+        }
+        Info<< nl;
+    }
+    else if (faMeshes.size() > 1)
+    {
+        Info<< "Detected finite-area meshes:";
+        for (const faMesh& areaMesh : faMeshes)
+        {
+            Info<< " [" << areaMesh.name() << "]";
+        }
+        Info<< nl;
     }
 
     const word dictName("setFieldsDict");
@@ -712,37 +763,45 @@ int main(int argc, char *argv[])
 
 
     // Default field values
+    if
+    (
+        const auto* eptr
+      = setFieldsDict.findEntry("defaultFieldValues", keyType::LITERAL)
+    )
     {
-        const entry* eptr =
-            setFieldsDict.findEntry("defaultFieldValues", keyType::LITERAL);
+        ITstream& is = eptr->stream();
 
-        if (eptr)
+        Info<< "Setting volume field default values" << endl;
+
+        PtrList<setCellField> defaultFieldValues
+        (
+            is,
+            setCellField::iNew(mesh, labelList::null())
+        );
+
+        for (const faMesh& areaMesh : faMeshes)
         {
-            ITstream& is = eptr->stream();
+            Info<< "Setting area field default values";
 
-            Info<< "Setting volume field default values" << endl;
-
-            PtrList<setCellField> defaultFieldValues
+            if
             (
-                is,
-                setCellField::iNew(mesh, labelList::null())
-            );
-
-            if (faMeshPtr)
+                const word& name = polyMesh::regionName(areaMesh.name());
+                !name.empty()
+            )
             {
-                const faMesh& areaMesh = faMeshPtr();
-                is.rewind();
-
-                Info<< "Setting area field default values" << endl;
-
-                PtrList<setAreaField> defaultFieldValues
-                (
-                    is,
-                    setAreaField::iNew(areaMesh, labelList::null())
-                );
+                Info<< " [" << name << "]";
             }
             Info<< endl;
+
+            is.rewind();
+
+            PtrList<setAreaField> defaultAreaFieldValues
+            (
+                is,
+                setAreaField::iNew(areaMesh, labelList::null())
+            );
         }
+        Info<< endl;
     }
 
 
@@ -768,11 +827,15 @@ int main(int argc, char *argv[])
 
             labelList selectedCells(subset.sortedToc());
 
-            Info<< "    Selected "
-                << returnReduce(selectedCells.size(), sumOp<label>())
-                << '/'
-                << returnReduce(mesh.nCells(), sumOp<label>())
-                << " cells" << nl;
+            {
+                FixedList<label, 2> stats;
+                stats[0] = selectedCells.size();
+                stats[1] = mesh.nCells();
+                reduce(stats, sumOp<label>());
+
+                Info<< "    Selected " << stats[0] << '/' << stats[1]
+                    << " cells" << nl;
+            }
 
             ITstream& is = region.dict().lookup("fieldValues");
 
@@ -806,10 +869,8 @@ int main(int argc, char *argv[])
                 setFaceField::iNew(mesh, selectedFaces)
             );
 
-            if (faMeshPtr)
+            for (const faMesh& areaMesh : faMeshes)
             {
-                const faMesh& areaMesh = faMeshPtr();
-
                 const labelUList& faceLabels = areaMesh.faceLabels();
 
                 // Transcribe from mesh faces to finite-area addressing
@@ -828,11 +889,15 @@ int main(int argc, char *argv[])
                 }
                 areaFaces.resize(nUsed);
 
-                Info<< "    Selected "
-                    << returnReduce(areaFaces.size(), sumOp<label>())
-                    << '/'
-                    << returnReduce(faceLabels.size(), sumOp<label>())
-                    << " area faces" << nl;
+                {
+                    FixedList<label, 2> stats;
+                    stats[0] = areaFaces.size();
+                    stats[1] = faceLabels.size();
+                    reduce(stats, sumOp<label>());
+
+                    Info<< "    Selected " << stats[0] << '/' << stats[1]
+                        << " area faces for " << areaMesh.name() << endl;
+                }
 
                 is.rewind();
 

bin/foamCleanFaMesh

@@ -0,0 +1,138 @@
+#!/bin/sh
+#------------------------------------------------------------------------------
+# =========                 |
+# \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+#  \\    /   O peration     |
+#   \\  /    A nd           | www.openfoam.com
+#    \\/     M anipulation  |
+#-------------------------------------------------------------------------------
+#     Copyright (C) 2011 OpenFOAM Foundation
+#     Copyright (C) 2025 OpenCFD Ltd.
+#------------------------------------------------------------------------------
+# License
+#     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+#
+# Script
+#     foamCleanFaMesh
+#
+# Description
+#    Remove the contents of the constant/finite-area/faMesh directory
+#    as per the Foam::faMesh::removeFiles() method.
+#
+#------------------------------------------------------------------------------
+usage() {
+    exec 1>&2
+    while [ "$#" -ge 1 ]; do echo "$1"; shift; done
+    cat <<USAGE
+
+Usage: ${0##*/} [OPTION]
+options:
+  -case <dir>           case directory, default is the cwd
+  -area-region <name>   area-mesh region
+  -dry-run | -n         report actions but do not remove
+  -help                 print the usage
+
+Remove the contents of the constant/finite-area/faMesh directory as per the
+Foam::faMesh::removeFiles() method.
+
+USAGE
+   exit 1
+}
+
+#------------------------------------------------------------------------------
+# Parse options
+unset caseDir areaRegion optDryRun
+
+while [ "$#" -gt 0 ]
+do
+    case "$1" in
+    -h | -help*)
+        usage
+        ;;
+    -dry-run | -n)
+        optDryRun="(dry-run) "
+        ;;
+
+    -case=*)
+        caseDir="${1#*=}"
+        ;;
+
+    -case)
+        [ "$#" -ge 2 ] || usage "'$1' option requires an argument"
+        cd "$2" 2>/dev/null || usage "directory does not exist:  '$2'"
+        caseDir=$2
+        shift
+        ;;
+
+    -area-region)
+        [ "$#" -ge 2 ] || usage "'$1' option requires an argument"
+        areaRegion=$2
+        shift
+        ;;
+
+    (*)
+        usage "unknown option/argument: '$*'"
+        ;;
+    esac
+    shift
+done
+
+#------------------------------------------------------------------------------
+
+# Remove files (mesh etc)
+# also remove .gz versions of the same files
+
+removeFiles()
+{
+    local directory="$1"
+
+    for i in \
+        faceLabels \
+        faBoundary \
+    ;
+    do
+        if [ -n "$optDryRun" ]
+        then
+            echo "${optDryRun} rm -rf $directory/{$i,$i.gz}"
+        else
+            rm -rf -- "$directory/$i" "$directory/$i.gz"
+        fi
+    done
+}
+
+#------------------------------------------------------------------------------
+
+meshDir="constant/finite-area/${areaRegion}${areaRegion:+/}faMesh"
+
+if [ -d "$meshDir" ]
+then
+    # [OK] has constant/finite-areaRegion/<region>/faMesh
+    :
+
+elif [ -n "$caseDir" ]
+then
+    # Specified -case, so no extra magic...
+    echo "Error: no <$meshDir> in $caseDir" 1>&2
+    exit 1
+
+else
+    # Try some other combinations
+    other="${meshDir#constant/}"
+
+    if [ -d "$other" ]
+    then
+        # Probably already within constant/
+        meshDir="$other}"
+    elif [ "${PWD##*/}" = faMesh ] && [ -z "$areaRegion" ]
+    then
+        # Apparently already within faMesh/
+        meshDir=.
+    fi
+fi
+
+
+echo "Cleaning ${caseDir:-.}/$meshDir" 1>&2
+
+removeFiles "$meshDir"
+
+#------------------------------------------------------------------------------

bin/foamCleanPolyMesh

@@ -7,7 +7,7 @@
 #    \\/     M anipulation  |
 #-------------------------------------------------------------------------------
 #     Copyright (C) 2011-2016 OpenFOAM Foundation
-#     Copyright (C) 2022 OpenCFD Ltd.
+#     Copyright (C) 2022,2025 OpenCFD Ltd.
 #------------------------------------------------------------------------------
 # License
 #     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -27,9 +27,10 @@ usage() {
 
 Usage: ${0##*/} [OPTION]
 options:
-  -case <dir>       specify alternative case directory, default is the cwd
-  -region <name>    specify alternative mesh region
-  -help             print the usage
+  -case <dir>           case directory, default is the cwd
+  -region <name>        mesh region
+  -dry-run | -n         report actions but do not remove
+  -help                 print the usage
 
 Remove the contents of the constant/polyMesh directory as per the
 Foam::polyMesh::removeFiles() method.
@@ -38,58 +39,101 @@ USAGE
    exit 1
 }
 
-unset caseDir regionName
+#------------------------------------------------------------------------------
+# Parse options
+unset caseDir regionName optDryRun
 
-# Parse a single option
 while [ "$#" -gt 0 ]
 do
     case "$1" in
     -h | -help*)
         usage
         ;;
+    -dry-run | -n)
+        optDryRun="(dry-run) "
+        ;;
+
+    -case=*)
+        caseDir="${1#*=}"
+        ;;
+
     -case)
+        caseDir="$2"
         [ "$#" -ge 2 ] || usage "'$1' option requires an argument"
         cd "$2" 2>/dev/null || usage "directory does not exist:  '$2'"
         caseDir=$2
-        shift 2
+        shift
         ;;
+
     -region)
         [ "$#" -ge 2 ] || usage "'$1' option requires an argument"
-        regionName=$2
-        shift 2
+        regionName="$2"
+        shift
         ;;
-    *)
+
+    (*)
         usage "unknown option/argument: '$*'"
         ;;
     esac
+    shift
 done
 
-meshDir=polyMesh
-if [ -n "$regionName" ]
-then
-    meshDir="$regionName/$meshDir"
-fi
+#------------------------------------------------------------------------------
 
-# If -case was specified: insist upon 'constant/polyMesh'
-if [ -n "$caseDir" ]
+# Remove files (mesh itself, modifiers, snappyHexMesh ones) and subdirectories
+# also remove .gz versions of the same files
+
+removeFiles()
+{
+    local directory="$1"
+
+    for i in \
+        points faces \
+        owner neighbour \
+        boundary \
+        cells \
+        cellZones faceZones pointZones \
+        meshModifiers \
+        parallelData \
+        sets \
+        cellLevel pointLevel \
+        level0Edge \
+        refinementHistory \
+        surfaceIndex \
+    ;
+    do
+        if [ -n "$optDryRun" ]
+        then
+            echo "${optDryRun} rm -rf $directory/{$i,$i.gz}"
+        else
+            rm -rf -- "$directory/$i" "$directory/$i.gz"
+        fi
+    done
+}
+
+#------------------------------------------------------------------------------
+
+meshDir="constant/${regionName}${regionName:+/}polyMesh"
+
+if [ -d "$meshDir" ]
 then
-    if [ -d constant/"$meshDir" ]
-    then
-        # Use constant/polyMesh
-        meshDir=constant/"$meshDir"
-    else
-       echo "Error: no 'constant/$meshDir' in $caseDir" 1>&2
-       exit 1
-    fi
+    # [OK] has constant/<region>/polyMesh
+    :
+
+elif [ -n "$caseDir" ]
+then
+    # Specified -case, so no extra magic...
+    echo "Error: no <$meshDir> in $caseDir" 1>&2
+    exit 1
+
 else
-    if [ -d constant/"$meshDir" ]
+    # Try some other combinations
+    other="${meshDir#constant/}"
+
+    if [ -d "$other" ]
     then
-        # Use constant/polyMesh
-        meshDir=constant/"$meshDir"
-    elif [ -d "$meshDir" ]
-    then
-        # Likely already in constant/ - do not adjust anything
-        :
+        # Probably already within constant/
+        meshDir="$other}"
     elif [ "${PWD##*/}" = polyMesh ] && [ -z "$regionName" ]
     then
         # Apparently already within polyMesh/
@@ -98,31 +142,8 @@ else
 fi
 
 
-# Remove files (mesh itself, modifiers, snappyHexMesh ones) and subdirectories
-# also remove .gz versions of the same files
 echo "Cleaning ${caseDir:-.}/$meshDir" 1>&2
 
-for i in \
-    points \
-    faces \
-    owner \
-    neighbour \
-    cells \
-    boundary \
-    pointZones \
-    faceZones \
-    cellZones \
-    meshModifiers \
-    parallelData \
-    sets \
-    cellLevel \
-    pointLevel \
-    level0Edge \
-    refinementHistory \
-    surfaceIndex \
-;
-do
-    rm -rf "$meshDir/$i" "$meshDir/$i.gz"
-done
+removeFiles "$meshDir"
 
 #------------------------------------------------------------------------------

bin/tools/CleanFunctions

@@ -108,54 +108,116 @@ cleanPostProcessing()
 }
 
 
+# ---------------
+# Remove constant/finite-area/faMesh or constant/finite-area/{region}/faMesh
+#
+# Accepts following options:
+#   -region <name>      The region name
+#   --                  End of options
+# ---------------
 cleanFaMesh()
 {
-    if [ -e constant/finite-area/faMesh ]
+    local region
+
+    # Parse options
+    while [ "$#" -gt 0 ]
+    do
+        case "$1" in
+        ('')  ;;                # Ignore empty option
+        (--)  shift; break ;;   # Stop option parsing
+
+        (-region)   region="$2"; shift ;;
+        (*) break ;;
+        esac
+        shift
+    done
+
+    # safety
+    if [ "$region" = "--" ]; then unset region; fi
+
+    local meshDir="constant/finite-area/${region}${region:+/}faMesh"
+
+    if [ -e "$meshDir" ]
     then
-        rm -rf constant/finite-area/faMesh
+        [ -n "$region" ] && echo "Clearing $meshDir" 1>&2
+        rm -rf -- "$meshDir"
     fi
-    if [ -e constant/faMesh ]
+
+    # Legacy location <constant/faMesh>
+    # - may still have remnant <constant/faMesh/faMeshDefinition>
+
+    meshDir="constant/faMesh"
+    if [ -e "$meshDir" ] && [ -z "$region" ]
     then
-        if [ -e constant/faMesh/faMeshDefinition ]
+        if [ -e "$meshDir"/faMeshDefinition ]
         then
-            # Old constant/faMesh location for faMeshDefinition still in use:
-            # - warn but don't remove anything
+            # VERY OLD LOCATION
             echo
-            echo "Warning: not removing constant/faMesh/"
+            echo "WARNING: not removing $meshDir/"
             echo "    It contains a 'faMeshDefinition' file"
-            echo "    Please relocate file(s) to system/ !!"
+            echo "    Please relocate file(s) to system/finite-area/ !!"
             echo
         else
             # Can remove constant/faMesh/ entirely (no faMeshDefinition)
-            rm -rf constant/faMesh
+            echo "Clearing $meshDir" 1>&2
+            rm -rf -- "$meshDir"
         fi
     fi
 }
 
 
+# ---------------
+# Remove constant/polyMesh or constant/<region>/polyMesh
+#
+# Accepts following options:
+#   -region <name>      The region name
+#   --                  End of options
+# ---------------
 cleanPolyMesh()
 {
-    if [ -e constant/polyMesh ]
+    local region
+
+    # Parse options
+    while [ "$#" -gt 0 ]
+    do
+        case "$1" in
+        ('')  ;;                # Ignore empty option
+        (--)  shift; break ;;   # Stop option parsing
+
+        (-region)   region="$2"; shift ;;
+        (*) break ;;
+        esac
+        shift
+    done
+
+    # safety
+    if [ "$region" = "--" ]; then unset region; fi
+
+    local meshDir="constant/${region}${region:+/}polyMesh"
+
+    if [ -e "$meshDir" ]
     then
-        if [ -e constant/polyMesh/blockMeshDict ] \
-        || [ -e constant/polyMesh/blockMeshDict.m4 ]
+        [ -n "$region" ] && echo "Clearing $meshDir" 1>&2
+
+        if [ -e "$meshDir"/blockMeshDict ] \
+        || [ -e "$meshDir"/blockMeshDict.m4 ]
         then
-            # Old constant/polyMesh location for blockMeshDict still in use:
-            # - warn but don't remove anything
+            # VERY OLD LOCATION
             echo
-            echo "Warning: not removing constant/polyMesh/"
+            echo "WARNING: not removing $meshDir/"
             echo "    It contains a 'blockMeshDict' or 'blockMeshDict.m4' file"
             echo "    Please relocate file(s) to system/ !!"
             echo
         else
             # Can remove constant/polyMesh/ entirely (no blockMeshDict)
-            rm -rf constant/polyMesh
+            rm -rf -- "$meshDir"
         fi
     fi
 
-    if [ -e system/blockMeshDict.m4 ]
+    meshDir="system${region:+/}${region}"
+    if [ -e "$meshDir"/blockMeshDict.m4 ]
     then
-        rm -f system/blockMeshDict
+        rm -f -- "$meshDir"/blockMeshDict
     fi
 }
 
@@ -212,7 +274,7 @@ cleanCase0()
 removeCase()
 {
     echo "Removing case ${1:-unknown}"
-    [ "$#" -ge 1 ] && rm -rf "$1"
+    [ "$#" -ge 1 ] && rm -rf -- "$1"
 }
 
 

bin/tools/RunFunctions

@@ -517,9 +517,11 @@ cloneParallelCase()
 }
 
 
+# ---------------
 # If 0.orig/ exists, copy (overwrite) into 0/ [ie, serial case]
 # * -processor : copy into processor directories instead
 # * -all : copy into serial and processor directories
+# ---------------
 restore0Dir()
 {
     if [ ! -d 0.orig ]
@@ -553,4 +555,61 @@ restore0Dir()
 }
 
 
+# ---------------
+# Helper routine to remove specified fields from the 0/ directory.
+# Often used in combination with foamListRegions.
+#
+# Accepts following options:
+#   -region <name>      The region name
+#   --                  End of options
+#
+# any remaining parameters are taken to be fields names
+# ---------------
+remove0DirFields()
+{
+    local region
+
+    # Parse options
+    while [ "$#" -gt 0 ]
+    do
+        case "$1" in
+        ('')  ;;                # Ignore empty option
+        (--)  shift; break ;;   # Stop option parsing
+
+        (-region)   region="$2"; shift ;;
+        (*) break ;;
+        esac
+        shift
+    done
+
+    # safety
+    if [ "$region" = "--" ]; then unset region; fi
+
+    if [ "$#" -eq 0 ]
+    then
+        echo "No fields specified for ${region:+region=$region }" 1>&2
+        return 0
+    fi
+
+    echo "Remove 0/ fields${region:+ [$region]} : $@" 1>&2
+
+    local subdir
+    for subdir in 0/"$region" processor*/0/"$region"
+    do
+        if [ -d "$subdir" ]
+        then
+            for field in $@  ## unquoted for IFS splitting [SIC]
+            do
+                # Cautious with removal
+                if [ -f "$subdir/$field" ]
+                then
+                    rm -f -- "$subdir/$field"
+                fi
+            done
+        fi
+    done
+    return 0
+}
+
+
 #------------------------------------------------------------------------------

etc/config.sh/bash_completion

@@ -140,6 +140,11 @@ _of_complete_()
         # Could use "foamListTimes -withZero", but still doesn't address ranges
         COMPREPLY=($(compgen -d -X '![-0-9]*' -- ${cur}))
         ;;
+    -area-region)
+        # Or: $(find system/finite-area -mindepth 1 -maxdepth 1 -type d 2>/dev/null | sed -e 's%.*/%%')
+        choices=$(\ls -d system/finite-area/*/ 2>/dev/null | sed -e 's%/$%%; s%^.*/%%')
+        COMPREPLY=($(compgen -W "$choices" -- ${cur}))
+        ;;
     -region)
         # Or: $(find system -mindepth 1 -maxdepth 1 -type d 2>/dev/null | sed -e 's%.*/%%')
         choices=$(\ls -d system/*/ 2>/dev/null | sed -e 's%/$%%; s%^.*/%%')

src/OpenFOAM/db/IOstreams/IOstreams/Ostream.H

@@ -341,22 +341,6 @@ inline Ostream& operator<<(Ostream& os, std::string_view s)
     return os;
 }
 
-//- Write operator for character span. Output like string data
-inline Ostream& operator<<(Ostream& os, stdFoam::span<char> s)
-{
-    os.writeQuoted(s.data(), s.size(), true);  // quoted
-    os.check("Foam::operator<<(Ostream&, stdFoam::span<char>)");
-    return os;
-}
-
-//- Write operator for const character span. Output like string data
-inline Ostream& operator<<(Ostream& os, stdFoam::span<const char> s)
-{
-    os.writeQuoted(s.data(), s.size(), true);  // quoted
-    os.check("Foam::operator<<(Ostream&, stdFoam::span<const char>)");
-    return os;
-}
-
 
 /*---------------------------------------------------------------------------*\
                        Manipulators (without arguments)

src/OpenFOAM/db/IOstreams/Pstreams/UPstream.txx

@@ -343,11 +343,22 @@ void Foam::UPstream::mpiGatherv
         }
         // Nothing further to do
     }
-    else if constexpr (UPstream_basic_dataType<Type>::value)
+    else if constexpr (UPstream_dataType<Type>::value)
     {
         // Restrict to basic (or aliased) MPI types to avoid recalculating
         // the list of counts/offsets.
 
+        // The sizing factor (constexpr) must be 1 otherwise
+        // [recvCounts,recvOffsets] are likely incorrect
+
+        constexpr std::streamsize count = UPstream_dataType<Type>::size(1);
+
+        static_assert
+        (
+            (count == 1),
+            "Code does not (yet) work with aggregate types"
+        );
+
         UPstream::mpi_gatherv
         (
             sendData,
@@ -356,7 +367,7 @@ void Foam::UPstream::mpiGatherv
             recvCounts,
             recvOffsets,
 
-            UPstream_basic_dataType<Type>::datatype_id,
+            UPstream_dataType<Type>::datatype_id,
             communicator
         );
     }
@@ -364,7 +375,8 @@ void Foam::UPstream::mpiGatherv
     {
         static_assert
         (
-            stdFoam::dependent_false_v<Type>, "Only basic MPI data types"
+            stdFoam::dependent_false_v<Type>,
+            "Only basic and user data types"
         );
     }
 }
@@ -392,11 +404,22 @@ void Foam::UPstream::mpiScatterv
         }
         // Nothing further to do
     }
-    else if constexpr (UPstream_basic_dataType<Type>::value)
+    else if constexpr (UPstream_dataType<Type>::value)
     {
         // Restrict to basic (or aliased) MPI types to avoid recalculating
         // the list of counts/offsets.
 
+        // The sizing factor (constexpr) must be 1 otherwise
+        // [sendCounts,sendOffsets] are likely incorrect
+
+        constexpr std::streamsize count = UPstream_dataType<Type>::size(1);
+
+        static_assert
+        (
+            (count == 1),
+            "Code does not (yet) work with aggregate types"
+        );
+
         UPstream::mpi_scatterv
         (
             sendData,
@@ -405,7 +428,7 @@ void Foam::UPstream::mpiScatterv
             recvData,
             recvCount,
 
-            UPstream_basic_dataType<Type>::datatype_id,
+            UPstream_dataType<Type>::datatype_id,
             communicator
         );
     }
@@ -413,7 +436,8 @@ void Foam::UPstream::mpiScatterv
     {
         static_assert
         (
-            stdFoam::dependent_false_v<Type>, "Only basic MPI data types"
+            stdFoam::dependent_false_v<Type>,
+            "Only basic and user data types"
         );
     }
 }

src/OpenFOAM/db/IOstreams/Pstreams/UPstreamTraits.H

@@ -354,7 +354,7 @@ struct UPstream_basic_dataType
         UPstream_alias_dataType<base>::datatype_id;
 
     //- The size in terms of the number of underlying data elements
-    static std::streamsize size(std::streamsize n) noexcept
+    static constexpr std::streamsize size(std::streamsize n) noexcept
     {
         if constexpr (UPstream_alias_dataType<T>::value)
         {
@@ -373,7 +373,10 @@ struct UPstream_basic_dataType
 template<> struct UPstream_basic_dataType<void> : UPstream_mpi_dataType<void>
 {
     using base = void;
-    static std::streamsize size(std::streamsize n) noexcept { return n; }
+    static constexpr std::streamsize size(std::streamsize n) noexcept
+    {
+        return n;
+    }
 };
 
 
@@ -410,7 +413,7 @@ struct UPstream_dataType
         UPstream_any_dataType<base>::datatype_id;
 
     //- The size in terms of the number of base data elements
-    static std::streamsize size(std::streamsize n) noexcept
+    static constexpr std::streamsize size(std::streamsize n) noexcept
     {
         if constexpr (UPstream_any_dataType<T>::value)
         {

src/OpenFOAM/db/IOstreams/Tstreams/ITstream.C

@@ -95,10 +95,12 @@ Foam::tokenList Foam::ITstream::parse_chars
     IOstreamOption streamOpt
 )
 {
-    ISpanStream is(s, nbytes, streamOpt);
-
     tokenList tokens;
-    parseStream(is, tokens);
+    if (s && nbytes > 0)  // extra safety
+    {
+        ISpanStream is(s, nbytes, streamOpt);
+        parseStream(is, tokens);
+    }
     return tokens;
 }
 
@@ -107,10 +109,19 @@ Foam::tokenList Foam::ITstream::parse_chars
 
 void Foam::ITstream::reset(const char* input, size_t nbytes)
 {
-    ISpanStream is(input, nbytes, static_cast<IOstreamOption>(*this));
+    tokenList tokens;
+    if (input && nbytes > 0)  // extra safety
+    {
+        ISpanStream is(input, nbytes, static_cast<IOstreamOption>(*this));
 
-    parseStream(is, static_cast<tokenList&>(*this));
-    ITstream::seek(0);  // rewind() bypassing virtual
+        parseStream(is, static_cast<tokenList&>(*this));
+        ITstream::seek(0);  // rewind() bypassing virtual
+    }
+    else
+    {
+        ITstream::seek(0);  // rewind() bypassing virtual
+        tokenList::clear();
+    }
 }
 
 
@@ -248,7 +259,10 @@ Foam::ITstream::ITstream
 :
     ITstream(streamOpt, name)
 {
-    reset(input, strlen(input));
+    if (input)
+    {
+        reset(input, strlen(input));
+    }
 }
 
 

src/OpenFOAM/db/IOstreams/Tstreams/ITstream.H

@@ -77,7 +77,8 @@ class ITstream
         //  but leave any excess capacity (ie, like reserve).
         void reserveCapacity(const label newCapacity);
 
-        //- Convert input sequence into a list of tokens,
+        //- Convert input sequence into a list of tokens.
+        //  Includes nullptr guard
         static tokenList parse_chars
         (
             const char* s,
@@ -87,6 +88,7 @@ class ITstream
 
         //- Convert input sequence into a list of tokens,
         //- using the existing stream format. Rewinds the stream
+        //  Includes nullptr guard
         void reset(const char* input, size_t nbytes);
 
         //- Failsafe read-access to token at specified location
@@ -175,32 +177,6 @@ public:
             reset(s.data(), s.size());
         }
 
-        //- Construct token list by parsing the input character sequence
-        //  Uses static parse function internally.
-        explicit ITstream
-        (
-            stdFoam::span<char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        :
-            ITstream(streamOpt)
-        {
-            reset(s.data(), s.size());
-        }
-
-        //- Construct token list by parsing the input character sequence
-        //  Uses static parse function internally.
-        explicit ITstream
-        (
-            stdFoam::span<const char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        :
-            ITstream(streamOpt)
-        {
-            reset(s.data(), s.size());
-        }
-
 
     // Additional constructors
 
@@ -255,17 +231,6 @@ public:
             return parse_chars(input.cdata(), input.size(), streamOpt);
         }
 
-        //- Create token list by parsing the input string
-        //- until no good tokens remain.
-        static tokenList parse
-        (
-            const std::string& input,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        {
-            return parse_chars(input.data(), input.size(), streamOpt);
-        }
-
         //- Create token list by parsing the input character sequence
         //- until no good tokens remain.
         static tokenList parse
@@ -274,7 +239,14 @@ public:
             IOstreamOption streamOpt = IOstreamOption()
         )
         {
-            return parse_chars(input, strlen(input), streamOpt);
+            if (input)
+            {
+                return parse_chars(input, strlen(input), streamOpt);
+            }
+            else
+            {
+                return tokenList();
+            }
         }
 
         //- Create token list by parsing the input character sequence
@@ -288,28 +260,6 @@ public:
             return parse_chars(s.data(), s.size(), streamOpt);
         }
 
-        //- Create token list by parsing the input character sequence
-        //- until no good tokens remain.
-        static tokenList parse
-        (
-            stdFoam::span<char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        {
-            return parse_chars(s.data(), s.size(), streamOpt);
-        }
-
-        //- Create token list by parsing the input character sequence
-        //- until no good tokens remain.
-        static tokenList parse
-        (
-            stdFoam::span<const char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        {
-            return parse_chars(s.data(), s.size(), streamOpt);
-        }
-
 
     // Member Functions
 
@@ -387,7 +337,7 @@ public:
         label& tokenIndex() noexcept { return tokenIndex_; }
 
         //- Set the token index (no checks). \return the previous value
-        label tokenIndex(const label num) noexcept
+        label tokenIndex(label num) noexcept
         {
             label old(tokenIndex_);
             tokenIndex_ = num;

src/OpenFOAM/db/IOstreams/memory/ISpanStream.H

@@ -123,20 +123,6 @@ public:
             stream_type(static_cast<buffer_type*>(this))
         {}
 
-        //- Construct (shallow copy) from span character content
-        explicit ispanstream(stdFoam::span<char> s)
-        :
-            buffer_type(const_cast<char*>(s.data()), s.size()),
-            stream_type(static_cast<buffer_type*>(this))
-        {}
-
-        //- Construct (shallow copy) from span character content
-        explicit ispanstream(stdFoam::span<const char> s)
-        :
-            buffer_type(const_cast<char*>(s.data()), s.size()),
-            stream_type(static_cast<buffer_type*>(this))
-        {}
-
 
     // Member Functions
 
@@ -325,26 +311,6 @@ public:
             ISpanStream(buffer.cdata(), buffer.size(), streamOpt)
         {}
 
-        //- Construct (shallow copy) from span character content
-        explicit ISpanStream
-        (
-            stdFoam::span<const char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        :
-            ISpanStream(s.data(), s.size(), streamOpt)
-        {}
-
-        //- Construct (shallow copy) from span character content
-        explicit ISpanStream
-        (
-            stdFoam::span<char> s,
-            IOstreamOption streamOpt = IOstreamOption()
-        )
-        :
-            ISpanStream(s.data(), s.size(), streamOpt)
-        {}
-
 
     // Member Functions
 
@@ -402,20 +368,6 @@ public:
             syncState();
         }
 
-        //- Reset input area to use data from span character content
-        void reset(stdFoam::span<char> s)
-        {
-            stream_.reset(s.data(), s.size());
-            syncState();
-        }
-
-        //- Reset input area to use data from span character content
-        void reset(stdFoam::span<const char> s)
-        {
-            stream_.reset(s.data(), s.size());
-            syncState();
-        }
-
         //- Rewind the stream, clearing any old errors
         virtual void rewind() override
         {

src/OpenFOAM/db/IOstreams/memory/memoryStreamBuffer.H

@@ -38,6 +38,7 @@ Description
 #include "DynamicList.H"
 
 #include <memory>
+#include <string_view>
 #include <string>
 #include <type_traits>
 

src/OpenFOAM/db/dictionary/dictionary.H

@@ -113,6 +113,7 @@ SeeAlso
 #include "label.H"
 #include "scalar.H"
 #include "regExpFwd.H"
+#include "Switch.H"
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 

src/OpenFOAM/db/error/messageStream.H

@@ -55,6 +55,8 @@ SourceFiles
 
 #include "label.H"
 #include "word.H"
+
+#include <string_view>
 #include <string>
 #include <iostream>
 

src/OpenFOAM/global/debug/simpleObjectRegistry.H

@@ -40,6 +40,7 @@ SourceFiles
 
 #include "Dictionary.H"
 #include "simpleRegIOobject.H"
+#include <string_view>
 #include <string>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.C

@@ -333,7 +333,7 @@ Foam::fileMonitor& Foam::fileOperation::monitor() const
 
 void Foam::fileOperation::mergeTimes
 (
-    const instantList& extraTimes,
+    const UList<instant>& extraTimes,
     const word& constantName,
     instantList& times
 )

src/OpenFOAM/global/fileOperations/fileOperation/fileOperation.H

@@ -198,8 +198,10 @@ protected:
         //- Merge two times
         static void mergeTimes
         (
-            const instantList& extraTimes,
+            const UList<instant>& extraTimes,
+            //! The "constant" name
             const word& constantName,
+            //! [in,out] Updated with any extra times
             instantList& times
         );
 
@@ -870,7 +872,13 @@ public:
             ) const;
 
             //- Get sorted list of times
-            virtual instantList findTimes(const fileName&, const word&) const;
+            virtual instantList findTimes
+            (
+                //! The directory to search
+                const fileName& directory,
+                //! The "constant" name
+                const word& constantName = "constant"
+            ) const;
 
             //- Find time instance where IOobject is located.
             //- The name of the IOobject can be empty, in which case only the

src/OpenFOAM/global/fileOperations/masterUncollatedFileOperation/masterUncollatedFileOperation.H

@@ -748,7 +748,13 @@ public:
         // Other
 
             //- Get sorted list of times
-            virtual instantList findTimes(const fileName&, const word&) const;
+            virtual instantList findTimes
+            (
+                //! The directory to search
+                const fileName& directory,
+                //! The "constant" name
+                const word& constantName = "constant"
+            ) const;
 
             //- Find time instance where IOobject is located.
             //- The name of the IOobject can be empty, in which case only the

src/OpenFOAM/include/addAllRegionOptions.H

@@ -11,7 +11,10 @@ License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
 
 Description
-    Add multi-region command-line options: -allRegions, -regions, -region
+    Add multi-region command-line options:
+      -allRegions | -all-regions
+      -regions
+      -region
 
 Required Classes
     - Foam::argList
@@ -24,10 +27,10 @@ See Also
 {
     Foam::argList::addBoolOption
     (
-        "all-regions",
+        "allRegions",
         "Use all regions in regionProperties"
     );
-    Foam::argList::addOptionCompat("all-regions", { "allRegions", -2506 });
+    Foam::argList::addOptionCompat("allRegions", { "all-regions", 0 });
 
     Foam::argList::addOption
     (

src/OpenFOAM/include/getAllRegionOptions.H

@@ -45,12 +45,19 @@ See Also
 
 wordList regionNames;
 {
-    // Local alias
-    auto& names = regionNames;
     // Exit or fallback if nothing matches
     constexpr bool exitOnNoMatches = true;
 
-    if (args.found("all-regions"))
+    // Local aliases
+    auto& names = regionNames;
+    const auto& fallback = Foam::polyMesh::defaultRegion;
+
+    if
+    (
+        // Handle both here (independent of which is an alias)
+        args.found("all-regions")
+     || args.found("allRegions")
+    )
     {
         names =
         (
@@ -81,11 +88,11 @@ wordList regionNames;
     {
         select.uniq();  // Normally a no-op
 
-        if (select.size() == 1 && select.front().isLiteral())
+        if (select.size() == 1 && select[0].isLiteral())
         {
             // Identical to -region NAME
             names.resize(1);
-            names.front() = select.front();
+            names[0] = select[0];
         }
         else if (select.size())
         {
@@ -116,12 +123,12 @@ wordList regionNames;
                     }
                     else
                     {
-                        InfoErr<< "... ignoring and using default region"
+                        InfoErr
+                            << "... ignoring and using default region"
                             << nl << endl;
 
-                        // Arbitrary fallback, but can handle this further on
                         names.resize(1);
-                        names.front() = Foam::polyMesh::defaultRegion;
+                        names[0] = fallback;
                     }
                 }
                 else
@@ -160,7 +167,7 @@ wordList regionNames;
                 else
                 {
                     names.resize(1);
-                    names.front() = Foam::polyMesh::defaultRegion;
+                    names[0] = fallback;
 
                     InfoErr
                         << "Warning: No regionProperties, "
@@ -169,17 +176,30 @@ wordList regionNames;
             }
         }
     }
-    else if (args.found("region"))
+    else
     {
+        // Single region option or fallback
         names.resize(1);
-        names.front() = args.get<word>("region");
+        auto& name = names[0];
+
+        if
+        (
+            !args.readIfPresent("region", name)
+        )
+        {
+            name = fallback;
+        }
     }
 
-    // Fallback to defaultRegion
+    // Final sanity checks and/or fallback
     if (names.empty())
     {
         names.resize(1);
-        names.front() = Foam::polyMesh::defaultRegion;
+        names[0] = fallback;
+    }
+    else if (names.size() == 1 && names[0].empty())
+    {
+        names[0] = fallback;
     }
 }
 

src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGAgglomerations/pairGAMGAgglomeration/pairGAMGAgglomerate.C

@@ -221,9 +221,14 @@ Foam::tmp<Foam::labelField> Foam::pairGAMGAgglomeration::agglomerate
     auto tcoarseCellMap = tmp<labelField>::New(nFineCells, -1);
     auto& coarseCellMap = tcoarseCellMap.ref();
 
+    // Small tolerance to account for faces potentially having slightly
+    // different truncation error in their weights from run to run
+    // (e.g. due to offloading). If all the largest faces per cell are
+    // within this tolerance use the first one. This guarantees repeatability.
+    const scalar tol = 1E-10;
+
     nCoarseCells = 0;
     label celli;
-
     for (label cellfi=0; cellfi<nFineCells; cellfi++)
     {
         // Change cell ordering depending on direction for this level
@@ -250,7 +255,7 @@ Foam::tmp<Foam::labelField> Foam::pairGAMGAgglomeration::agglomerate
                 (
                     coarseCellMap[upperAddr[facei]] < 0
                  && coarseCellMap[lowerAddr[facei]] < 0
-                 && faceWeights[facei] > maxFaceWeight
+                 && faceWeights[facei] > maxFaceWeight*(1.0 + tol)
                 )
                 {
                     // Match found. Pick up all the necessary data
@@ -282,7 +287,7 @@ Foam::tmp<Foam::labelField> Foam::pairGAMGAgglomeration::agglomerate
                 {
                     label facei = cellFaces[faceOs];
 
-                    if (faceWeights[facei] > clusterMaxFaceCoeff)
+                    if (faceWeights[facei] > clusterMaxFaceCoeff*(1.0 + tol))
                     {
                         clusterMatchFaceNo = facei;
                         clusterMaxFaceCoeff = faceWeights[facei];

src/OpenFOAM/parallel/globalIndex/globalIndex.txx

@@ -27,6 +27,7 @@ License
 \*---------------------------------------------------------------------------*/
 
 #include "globalIndex.H"
+#include <functional>
 
 // * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
@@ -696,159 +697,94 @@ void Foam::globalIndex::mpiGather
     const UList<Type>& sendData,
     OutputContainer& allData,
     const label comm,
-    UPstream::commsTypes commsType,
-    const int tag
+    [[maybe_unused]] UPstream::commsTypes commsType,
+    [[maybe_unused]] const int tag
 ) const
 {
-    if (!UPstream::parRun())
+    if (!UPstream::is_parallel(comm))
     {
         // Serial: direct copy
         allData = sendData;
         return;
     }
 
-    // MPI_Gatherv requires contiguous data, but a byte-wise transfer can
-    // quickly exceed the 'int' limits used for MPI sizes/offsets.
-    // Thus gather label/scalar components when possible to increase the
-    // effective size limit.
-    //
-    // Note: cannot rely on pTraits (cmptType, nComponents) since this method
-    // needs to compile (and work) even with things like strings etc.
-
-    // Single char ad hoc "enum":
-    // - b(yte):  gather bytes
-    // - f(loat): gather scalars components
-    // - i(nt):   gather label components
-    // - 0:       gather with Pstream read/write etc.
-
-    List<int> recvCounts;
-    List<int> recvOffsets;
-
-    char dataMode(0);
-    int nCmpts(0);
-
-    if constexpr (is_contiguous_v<Type>)
+    if (UPstream::master(comm))
     {
-        if constexpr (is_contiguous_scalar<Type>::value)
-        {
-            dataMode = 'f';
-            nCmpts = static_cast<int>(sizeof(Type)/sizeof(scalar));
-        }
-        else if constexpr (is_contiguous_label<Type>::value)
-        {
-            dataMode = 'i';
-            nCmpts = static_cast<int>(sizeof(Type)/sizeof(label));
-        }
-        else
-        {
-            dataMode = 'b';
-            nCmpts = static_cast<int>(sizeof(Type));
-        }
+        allData.resize_nocopy(offsets_.back());  // == totalSize()
+    }
+    else
+    {
+        allData.clear();  // zero-size on non-master
+    }
+
+    if constexpr (UPstream_dataType<Type>::value)
+    {
+        // Restrict to basic (or aliased) MPI types
+        // - simplifies calculating counts/offsets
+        //   and can call UPstream::mpiGatherv directly
+
+        // The sizing factor is constexpr
+        constexpr std::streamsize count = UPstream_dataType<Type>::size(1);
+
+        static_assert
+        (
+            (count == 1),
+            "Code does not (yet) work with aggregate types"
+        );
+
+        List<int> recvCounts;
+        List<int> recvOffsets;
 
-        // Offsets must fit into int
         if (UPstream::master(comm))
         {
-            const globalIndex& globalAddr = *this;
+            // Must be same as Pstream::nProcs(comm), at least on master!
+            // if (UPstream::nProcs(comm) != this->nProcs()) ...
 
-            if (globalAddr.totalSize() > (INT_MAX/nCmpts))
-            {
-                // Offsets do not fit into int - revert to manual.
-                dataMode = 0;
-            }
-            else
-            {
-                // Must be same as Pstream::nProcs(comm), at least on master!
-                const label nproc = globalAddr.nProcs();
+            recvCounts.resize(offsets_.size()-1);
+            recvOffsets.resize(offsets_.size());
 
-                allData.resize_nocopy(globalAddr.totalSize());
+            // Copy offsets
+            std::copy(offsets_.begin(), offsets_.end(), recvOffsets.begin());
 
-                recvCounts.resize(nproc);
-                recvOffsets.resize(nproc+1);
+            // Calculate sizes. Currently without std::minus <functional>
+            std::transform
+            (
+                offsets_.begin()+1, offsets_.end(),
+                offsets_.begin(), recvCounts.begin(),
+                std::minus<>{}
+            );
 
-                for (label proci = 0; proci < nproc; ++proci)
-                {
-                    recvCounts[proci] = globalAddr.localSize(proci)*nCmpts;
-                    recvOffsets[proci] = globalAddr.localStart(proci)*nCmpts;
-                }
-                recvOffsets[nproc] = globalAddr.totalSize()*nCmpts;
-
-                // Assign local data directly
-
-                recvCounts[0] = 0;  // ie, ignore for MPI_Gatherv
-                SubList<Type>(allData, globalAddr.range(0)) =
-                    SubList<Type>(sendData, globalAddr.range(0));
-            }
+            // FUTURE .. fix sizes and offsets by the element factor...
+            // if constexpr (UPstream_basic_dataType<Type>::size(1) > 1)
         }
 
-        // Consistent information for everyone
-        UPstream::broadcast(&dataMode, 1, comm);
+        int sendSize = static_cast<int>(sendData.size());
+
+        // Note we let MPI_Gatherv copy back the local data as well...
+
+        UPstream::mpiGatherv
+        (
+            sendData.cdata(),
+            sendSize,
+            allData.data(),
+            recvCounts,
+            recvOffsets,
+            comm
+        );
     }
-
-    // Dispatch
-    switch (dataMode)
+    else
     {
-        case 'b':   // Byte-wise
-        {
-            UPstream::mpiGatherv
-            (
-                sendData.cdata_bytes(),
-                sendData.size_bytes(),
-                allData.data_bytes(),
-                recvCounts,
-                recvOffsets,
-                comm
-            );
-            break;
-        }
-        case 'f':   // Float (scalar) components
-        {
-            typedef scalar cmptType;
-
-            UPstream::mpiGatherv
-            (
-                reinterpret_cast<const cmptType*>(sendData.cdata()),
-                (sendData.size()*nCmpts),
-                reinterpret_cast<cmptType*>(allData.data()),
-                recvCounts,
-                recvOffsets,
-                comm
-            );
-            break;
-        }
-        case 'i':   // Int (label) components
-        {
-            typedef label cmptType;
-
-            UPstream::mpiGatherv
-            (
-                reinterpret_cast<const cmptType*>(sendData.cdata()),
-                (sendData.size()*nCmpts),
-                reinterpret_cast<cmptType*>(allData.data()),
-                recvCounts,
-                recvOffsets,
-                comm
-            );
-            break;
-        }
-        default:    // Regular (manual) gathering
-        {
-            globalIndex::gather
-            (
-                offsets_,  // needed on master only
-                comm,
-                UPstream::allProcs(comm),   // All communicator ranks
-                sendData,
-                allData,
-                tag,
-                commsType
-            );
-            break;
-        }
-    }
-
-    if (!UPstream::master(comm))
-    {
-        allData.clear();  // safety: zero-size on non-master
+        // Regular (manual) gathering
+        globalIndex::gather
+        (
+            offsets_,  // needed on master only
+            comm,
+            UPstream::allProcs(comm),   // All communicator ranks
+            sendData,
+            allData,
+            tag,
+            commsType
+        );
     }
 }
 

src/OpenFOAM/primitives/bools/Switch/Switch.H

@@ -43,6 +43,9 @@ SourceFiles
 #include "bool.H"
 #include "stdFoam.H"
 
+#include <string_view>
+#include <string>
+
 // Avoid any pre-processor conflicts with enum names
 #undef FALSE
 #undef TRUE

src/OpenFOAM/primitives/strings/lists/CStringList.H

@@ -58,6 +58,9 @@ Description
 
 #include <algorithm>  // std::copy
 #include <utility>    // std::initializer_list
+#include <vector>
+#include <string_view>
+#include <string>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
@@ -93,6 +96,11 @@ class CStringList
         //  \return location one-past end of dest (ie, the next destination)
         static inline char* stringCopy(char* dest, const char* src);
 
+        //- Copy string characters into dest as NUL-terminated string.
+        //
+        //  \return location one-past end of dest (ie, the next destination)
+        static inline char* stringCopy(char *dest, std::string_view src);
+
         //- Copy string characters into dest as NUL-terminated string.
         //  Forces conversion of std::sub_match to string form
         //
@@ -133,9 +141,17 @@ public:
         template<class StringType>
         inline explicit CStringList(const UList<StringType>& input);
 
+        //- Copy construct from a list of string_views
+        //  Copies the input characters.
+        inline explicit CStringList(const UList<std::string_view>& input);
+
+        //- Copy construct from a list of string_views
+        //  Copies the input characters.
+        inline explicit CStringList(const std::vector<std::string_view>& input);
+
         //- Copy construct from a list of sub-string references
         //  Copies the input characters.
-        explicit CStringList(const SubStrings& input);
+        inline explicit CStringList(const SubStrings& input);
 
 
     //- Destructor. Invokes clear() to free memory.
@@ -157,6 +173,9 @@ public:
         //- Return the number of C-strings (ie, argc)
         int size() const noexcept { return argc_; }
 
+        //- The flattened character content, with interspersed nul-chars
+        inline std::string_view view() const;
+
         //- The flattened character content, with interspersed nul-chars
         const char* cdata_bytes() const noexcept { return data_; }
 

src/OpenFOAM/primitives/strings/lists/CStringList.cxx

@@ -28,16 +28,6 @@ License
 #include "CStringList.H"
 #include "Ostream.H"
 
-// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
-
-Foam::CStringList::CStringList(const SubStrings& input)
-:
-    CStringList()
-{
-    resetContent(input);
-}
-
-
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
 // Largely identical to resetContent() except with 'c-string'

src/OpenFOAM/primitives/strings/lists/CStringListI.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2016-2024 OpenCFD Ltd.
+    Copyright (C) 2016-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -35,6 +35,14 @@ inline char* Foam::CStringList::stringCopy(char* dest, const char* src)
 }
 
 
+inline char* Foam::CStringList::stringCopy(char *dest, std::string_view src)
+{
+    dest = std::copy_n(src.data(), src.size(), dest);
+    *(dest++) = '\0';
+    return dest;
+}
+
+
 inline char* Foam::CStringList::stringCopy(char *dest, const std::string& src)
 {
     dest = std::copy_n(src.data(), src.size(), dest);
@@ -90,6 +98,33 @@ inline Foam::CStringList::CStringList(const UList<StringType>& input)
 }
 
 
+inline Foam::CStringList::CStringList(const UList<std::string_view>& input)
+:
+    CStringList()
+{
+    resetContent(input);
+}
+
+
+inline Foam::CStringList::CStringList
+(
+    const std::vector<std::string_view>& input
+)
+:
+    CStringList()
+{
+    resetContent(input);
+}
+
+
+inline Foam::CStringList::CStringList(const SubStrings& input)
+:
+    CStringList()
+{
+    resetContent(input);
+}
+
+
 // * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
 
 inline Foam::CStringList::~CStringList()
@@ -100,6 +135,12 @@ inline Foam::CStringList::~CStringList()
 
 // * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
 
+inline std::string_view Foam::CStringList::view() const
+{
+    return std::string_view(data_, nbytes_);
+}
+
+
 inline void Foam::CStringList::clear()
 {
     argc_ = 0;

src/OpenFOAM/primitives/strings/lists/SubStrings.H

@@ -37,6 +37,7 @@ Description
 
 #include <regex>    // For std::ssub_match
 #include <memory>
+#include <string_view>
 #include <string>
 #include <vector>
 

src/OpenFOAM/primitives/strings/regex/regExpCxx.H

@@ -69,6 +69,7 @@ SourceFiles
 #define Foam_regExpCxx_H
 
 #include <regex>
+#include <string_view>
 #include <string>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/OpenFOAM/primitives/strings/string/string.H

@@ -54,6 +54,7 @@ SourceFiles
 #include "Hasher.H"
 #include <cstdlib>
 #include <cstring>
+#include <string_view>
 #include <string>
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/OpenFOAM/primitives/strings/stringOps/stringOpsSort.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017 OpenCFD Ltd.
+    Copyright (C) 2017-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -46,85 +46,106 @@ namespace Foam
 namespace stringOps
 {
 
-    //- 'Natural' compare for C-strings
-    //  Uses algorithm and code from Jan-Marten Spit <jmspit@euronet.nl>
-    //
-    //  In the 'natural' comparison, strings are compared alphabetically
-    //  and numerically. Thus 'file010.txt' sorts after 'file2.txt'
-    //
-    //  \param s1 left string
-    //  \param s2 right string
+//- 'Natural' compare for C-strings
+//  Uses algorithm and code from Jan-Marten Spit <jmspit@euronet.nl>
+//
+//  In the 'natural' comparison, strings are compared alphabetically
+//  and numerically. Thus 'file010.txt' sorts after 'file2.txt'
+//
+//  \param s1 left string
+//  \param s2 right string
+//  \return -1 when s1 < s2, 0 when s1 == s2, 1 when s1 > s2
+int natstrcmp(const char* s1, const char* s2);
+
+
+//- Encapsulation of natural order sorting for algorithms
+struct natural_sort
+{
+    //- Natural compare for std::string
     //  \return -1 when s1 < s2, 0 when s1 == s2, 1 when s1 > s2
-    int natstrcmp(const char* s1, const char* s2);
-
-
-    //- Encapsulation of natural order sorting for algorithms
-    struct natural_sort
+    static inline int compare
+    (
+        const std::string& s1,
+        const std::string& s2
+    )
     {
-        //- Natural compare for std::string
-        //  \return -1 when s1 < s2, 0 when s1 == s2, 1 when s1 > s2
-        static inline int compare
-        (
-            const std::string& s1,
-            const std::string& s2
-        )
-        {
-            return natstrcmp(s1.data(), s2.data());
-        }
+        return stringOps::natstrcmp(s1.data(), s2.data());
+    }
 
-        //- Default (forward) natural sorting
+    //- Natural compare two strings for a less-than relationship
+    static inline bool less
+    (
+        const std::string& s1,
+        const std::string& s2
+    )
+    {
+        return (natural_sort::compare(s1, s2) < 0);
+    }
+
+    //- Natural compare two strings for a greater-than relationship
+    static inline bool greater
+    (
+        const std::string& s1,
+        const std::string& s2
+    )
+    {
+        return (natural_sort::compare(s1, s2) > 0);
+    }
+
+    //- Default (forward) natural sorting
+    bool operator()(const std::string& s1, const std::string& s2) const
+    {
+        return (natural_sort::compare(s1, s2) < 0);
+    }
+
+    //- Reverse natural sorting
+    struct reverse
+    {
+        //- Reverse natural sorting
         bool operator()(const std::string& s1, const std::string& s2) const
         {
-            return natural_sort::compare(s1, s2) < 0;
+            return (natural_sort::compare(s1, s2) > 0);
         }
-
-        //- Reverse natural sorting
-        struct reverse
-        {
-            //- Reverse natural sorting
-            bool operator()(const std::string& s1, const std::string& s2) const
-            {
-                return natural_sort::compare(s1, s2) > 0;
-            }
-        };
-
-
-        //- A list compare binary predicate for natural sort
-        template<class T>
-        struct less
-        {
-            const UList<T>& values;
-
-            less(const UList<T>& list)
-            :
-                values(list)
-            {}
-
-            bool operator()(const label a, const label b) const
-            {
-                return natural_sort::compare(values[a], values[b]) < 0;
-            }
-        };
-
-
-        //- A list compare binary predicate for reverse natural sort
-        template<class T>
-        struct greater
-        {
-            const UList<T>& values;
-
-            greater(const UList<T>& list)
-            :
-                values(list)
-            {}
-
-            bool operator()(const label a, const label b) const
-            {
-                return natural_sort::compare(values[a], values[b]) > 0;
-            }
-        };
     };
 
+
+    //- A UList compare binary predicate for natural sort
+    template<class T>
+    struct list_less
+    {
+        const UList<T>& values;
+
+        list_less(const UList<T>& list) noexcept
+        :
+            values(list)
+        {}
+
+        bool operator()(label a, label b) const
+        {
+            return (natural_sort::compare(values[a], values[b]) < 0);
+        }
+    };
+
+
+    //- A Ulist compare binary predicate for reverse natural sort
+    template<class T>
+    struct list_greater
+    {
+        const UList<T>& values;
+
+        list_greater(const UList<T>& list) noexcept
+        :
+            values(list)
+        {}
+
+        bool operator()(label a, label b) const
+        {
+            return (natural_sort::compare(values[a], values[b]) > 0);
+        }
+    };
+};
+
+
 } // End namespace stringOps
 } // End namespace Foam
 

src/Pstream/mpi/UPstreamGatherScatter.C

@@ -28,33 +28,45 @@ License
 #include "Pstream.H"
 #include "PstreamGlobals.H"
 #include "UPstreamWrapping.H"
+#include "vector.H"  // for debugging
+
+#undef STRINGIFY
+#undef STRING_QUOTE
+
+#define STRINGIFY(content) #content
+#define STRING_QUOTE(input) STRINGIFY(input)
 
 // * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
 
-static inline bool is_basic_dataType(Foam::UPstream::dataTypes id) noexcept
+namespace
+{
+
+inline bool is_nonAggregate(Foam::UPstream::dataTypes id) noexcept
 {
     return
     (
         int(id) >= int(Foam::UPstream::dataTypes::Basic_begin)
      && int(id)  < int(Foam::UPstream::dataTypes::Basic_end)
+    )
+    ||
+    (
+        int(id) >= int(Foam::UPstream::dataTypes::User_begin)
+     && int(id)  < int(Foam::UPstream::dataTypes::User_end)
     );
 }
 
-namespace
-{
-
-using namespace Foam;
-
 // Local function to print some error information
 inline void printErrorNonIntrinsic
 (
     const char* context,
-    UPstream::dataTypes dataTypeId
+    Foam::UPstream::dataTypes dataTypeId
 )
 {
+    using namespace Foam;
+
     FatalError
         << "Bad input for " << context << ": likely a programming problem\n"
-        << "    Non-intrinsic data (" << int(dataTypeId) << ")\n"
+        << "    Non-intrinsic/non-user data (type:" << int(dataTypeId) << ")\n"
         << Foam::endl;
 }
 
@@ -214,19 +226,37 @@ void Foam::UPstream::mpi_gatherv
 {
     MPI_Datatype datatype = PstreamGlobals::getDataType(dataTypeId);
 
-    if
-    (
-        FOAM_UNLIKELY
-        (
-            !is_basic_dataType(dataTypeId)
-        )
-    )
+    // Runtime assert that we are not using aggregated data types
+    if (FOAM_UNLIKELY(!is_nonAggregate(dataTypeId)))
     {
         FatalErrorInFunction;
         printErrorNonIntrinsic("MPI_Gatherv()", dataTypeId);
         FatalError << Foam::abort(FatalError);
     }
 
+    const label np = UPstream::nProcs(communicator);
+
+    // For total-size calculation,
+    // don't rely on recvOffsets being (np+1)
+    const int totalSize =
+    (
+        (UPstream::master(communicator) && np > 1)
+      ? (recvOffsets[np-1] + recvCounts[np-1])
+      : 0
+    );
+
+    if (FOAM_UNLIKELY(UPstream::debug))
+    {
+        Perr<< "[mpi_gatherv] :"
+            << " type:" << int(dataTypeId)
+            << " count:" << sendCount
+            << " total:" << totalSize
+            << " comm:" << communicator
+            << " recvCounts:" << flatOutput(recvCounts)
+            << " recvOffsets:" << flatOutput(recvOffsets)
+            << Foam::endl;
+    }
+
     {
         PstreamDetail::gatherv
         (
@@ -235,6 +265,48 @@ void Foam::UPstream::mpi_gatherv
             datatype, communicator
         );
     }
+
+    // Extended debugging. Limit to master:
+
+    #if 0
+    if (FOAM_UNLIKELY(UPstream::debug))
+    {
+        if (UPstream::master(communicator))
+        {
+            switch (dataTypeId)
+            {
+                #undef  dataPrinter
+                #define dataPrinter(enumType, nativeType)           \
+                case UPstream::dataTypes::enumType :                \
+                {                                                   \
+                    UList<nativeType> combined                      \
+                    (                                               \
+                        static_cast<nativeType*>(recvData),         \
+                        totalSize                                   \
+                    );                                              \
+                                                                    \
+                    Info<< "[mpi_gatherv] => "                      \
+                    "List<" STRING_QUOTE(nativeType) "> ";          \
+                    combined.writeList(Info) << Foam::endl;         \
+                                                                    \
+                    break;                                          \
+                }
+
+                // Some common types
+                dataPrinter(type_int32, int32_t);
+                dataPrinter(type_int64, int64_t);
+                dataPrinter(type_float, float);
+                dataPrinter(type_double, double);
+                dataPrinter(type_3float, floatVector);
+                dataPrinter(type_3double, doubleVector);
+
+                // Some other type
+                default: break;
+                #undef dataPrinter
+            }
+        }
+    }
+    #endif
 }
 
 
@@ -255,13 +327,8 @@ void Foam::UPstream::mpi_scatterv
 {
     MPI_Datatype datatype = PstreamGlobals::getDataType(dataTypeId);
 
-    if
-    (
-        FOAM_UNLIKELY
-        (
-            !is_basic_dataType(dataTypeId)
-        )
-    )
+    // Runtime assert that we are not using aggregated data types
+    if (FOAM_UNLIKELY(!is_nonAggregate(dataTypeId)))
     {
         FatalErrorInFunction;
         printErrorNonIntrinsic("MPI_Scatterv()", dataTypeId);

src/conversion/Make/files

@@ -16,6 +16,6 @@ starcd/STARCDMeshWriter.C
 
 polyDualMesh/polyDualMesh.C
 
-vtk/output/foamVtkSurfaceFieldWriter.C
+vtk/output/foamVtkSurfaceFieldWriter.cxx
 
 LIB = $(FOAM_LIBBIN)/libconversion

src/conversion/ensight/output/ensightOutputAreaField.H

@@ -98,7 +98,7 @@ bool writeAreaField
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "ensightOutputAreaFieldTemplates.C"
+    #include "ensightOutputAreaField.txx"
 #endif
 
 #endif

src/conversion/ensight/output/ensightOutputVolField.H

@@ -177,7 +177,7 @@ bool writePointField
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "ensightOutputVolFieldTemplates.C"
+    #include "ensightOutputVolField.txx"
 #endif
 
 #endif

src/conversion/vtk/adaptor/foamVtkTools.H

@@ -39,7 +39,7 @@ Note
 
 SourceFiles
     foamVtkToolsI.H
-    foamVtkToolsTemplates.C
+    foamVtkTools.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -358,7 +358,7 @@ void Foam::vtk::Tools::remapTuple<Foam::symmTensor>(double data[])
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "foamVtkToolsTemplates.C"
+    #include "foamVtkTools.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/conversion/vtk/adaptor/foamVtkVtuAdaptor.H

@@ -39,7 +39,7 @@ Note
 
 SourceFiles
     foamVtkVtuAdaptorI.H
-    foamVtkVtuAdaptorTemplates.C
+    foamVtkVtuAdaptor.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -156,7 +156,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "foamVtkVtuAdaptorTemplates.C"
+    #include "foamVtkVtuAdaptor.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/conversion/vtk/output/foamVtkGenericPatchGeoFieldsWriter.H

@@ -32,7 +32,7 @@ Description
     Caution, currently only works properly for indirect patches.
 
 SourceFiles
-    foamVtkGenericPatchGeoFieldsWriter.C
+    foamVtkGenericPatchGeoFieldsWriter.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -117,7 +117,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "foamVtkGenericPatchGeoFieldsWriter.C"
+    #include "foamVtkGenericPatchGeoFieldsWriter.txx"
 #endif
 
 

src/conversion/vtk/output/foamVtkInternalWriter.H

@@ -44,7 +44,7 @@ See Also
     Foam::vtk::internalMeshWriter
 
 SourceFiles
-    foamVtkInternalWriterTemplates.C
+    foamVtkInternalWriter.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -183,7 +183,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "foamVtkInternalWriterTemplates.C"
+    #include "foamVtkInternalWriter.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/conversion/vtk/output/foamVtkPatchWriter.H

@@ -43,7 +43,7 @@ See Also
     Foam::vtk::patchMeshWriter
 
 SourceFiles
-    foamVtkPatchWriterTemplates.C
+    foamVtkPatchWriter.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -202,7 +202,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "foamVtkPatchWriterTemplates.C"
+    #include "foamVtkPatchWriter.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/conversion/vtk/output/foamVtkSurfaceFieldWriter.H

@@ -47,7 +47,7 @@ Note
     may be addressed using ghost points.
 
 SourceFiles
-    surfaceFieldWriter.C
+    foamVtkSurfaceFieldWriter.cxx
 
 \*---------------------------------------------------------------------------*/
 

src/faOptions/Make/files

@@ -9,7 +9,7 @@ faceSetOption/faceSetOption.C
 derivedSources=sources/derived
 
 $(derivedSources)/externalHeatFluxSource/externalHeatFluxSource.C
-$(derivedSources)/jouleHeatingSource/jouleHeatingSource.C
+$(derivedSources)/jouleHeatingSource/jouleHeatingSource.cxx
 $(derivedSources)/contactHeatFluxSource/contactHeatFluxSource.C
 $(derivedSources)/externalFileSource/externalFileSource.C
 

src/faOptions/faOption/faOption.C

@@ -81,6 +81,33 @@ Foam::fa::option::option
     active_(dict.getOrDefault("active", true)),
     log(true)
 {
+    // Suffix hint for variable names
+    if
+    (
+        coeffs_.readIfPresent("suffixing", suffixHint_)
+     || dict.readIfPresent("suffixing", suffixHint_)
+    )
+    {
+        Switch sw = Switch::find(suffixHint_);
+
+        if (sw.good())
+        {
+            if (!sw)  // No suffix
+            {
+                suffixHint_.clear();
+            }
+        }
+        else if (suffixHint_ == "default")
+        {
+            sw = true;
+        }
+
+        if (sw)  // Default suffix
+        {
+            suffixHint_ = '_' + regionName_;
+        }
+    }
+
     if (dict.readIfPresent("area", areaName_))
     {
         if (!sameRegionNames(areaName_, defaultAreaName))
@@ -95,9 +122,14 @@ Foam::fa::option::option
         }
     }
 
-    Log << incrIndent << indent << "Source: " << name_
-        << " [" << polyMesh::regionName(areaName_) << ']' << endl
-        << decrIndent;
+    Log << incrIndent << indent << "Source: " << name_;
+
+    if (!polyMesh::regionName(areaName_).empty())
+    {
+        Log<< " [" << areaName_ << ']';
+    }
+
+    Info<< decrIndent << endl;
 }
 
 
@@ -117,13 +149,20 @@ Foam::autoPtr<Foam::fa::option> Foam::fa::option::New
     coeffs.readIfPresent("area", areaName);
 
     Info<< indent
-        << "Selecting finite-area option, type " << modelType
-        << " [" << polyMesh::regionName(areaName) << ']';
+        << "Selecting finite-area option, type " << modelType;
 
-    if (!sameRegionNames(areaName, defaultAreaName))
+    if (sameRegionNames(areaName, defaultAreaName))
     {
-        Info<< " != " << defaultAreaName << nl;
+        if (!polyMesh::regionName(areaName).empty())
+        {
+            Info<< " [" << areaName << ']';
+        }
     }
+    else
+    {
+        Info<< " [" << areaName << "] != [" << defaultAreaName << ']';
+    }
+
     Info<< endl;
 
     mesh.time().libs().open

src/faOptions/faOption/faOption.H

@@ -65,10 +65,13 @@ Usage
                     --> the selected faOption settings | dictionary | no | -
       active   | Flag to (de)activate faOption         | bool  | no   | true
       log      | Flag to log faOption-related info     | bool  | no   | true
+      suffixing | Suffix hint for option variables     | word  | no   | -
     \endtable
 
 Note
   - Source/sink options are to be added to the right-hand side of equations.
+  - Suffixing (true|false|none|default|...) currently selects between
+    no suffix and ('_'+region).
 
 SourceFiles
     faOption.C
@@ -136,6 +139,9 @@ protected:
         //- The model region name (finite-area)
         word regionName_;
 
+        //- Suffix hint for variable names (default: "")
+        word suffixHint_;
+
 
     // Protected Member Functions
 
@@ -273,7 +279,7 @@ public:
         //- The source name
         const word& name() const noexcept { return name_; }
 
-        //- Return const access to the mesh database
+        //- Return const access to the volume mesh
         const fvMesh& mesh() const noexcept { return mesh_; }
 
         //- Return dictionary
@@ -304,6 +310,18 @@ public:
         inline bool active(bool on) noexcept;
 
 
+    // Helper Functions
+
+        //- The suffix hint when generating variable names
+        const word& suffixHint() const noexcept { return suffixHint_; }
+
+        //- Return the concatenation of \p base and the suffix hint
+        inline word suffixed(const char* base) const;
+
+        //- Return the concatenation of \p base and the suffix hint
+        inline word suffixed(const std::string& base) const;
+
+
     // Checks
 
         //- Is the source active?

src/faOptions/faOption/faOptionI.H

@@ -61,4 +61,18 @@ inline const Foam::volSurfaceMapping& Foam::fa::option::vsm() const
 }
 
 
+inline Foam::word
+Foam::fa::option::suffixed(const char* base) const
+{
+    return word(base + suffixHint_);
+}
+
+
+inline Foam::word
+Foam::fa::option::suffixed(const std::string& base) const
+{
+    return word(base + suffixHint_);
+}
+
+
 // ************************************************************************* //

src/faOptions/faOption/faOptions.C

@@ -27,7 +27,6 @@ License
 
 #include "faOptions.H"
 #include "faMesh.H"
-#include "faMeshesRegistry.H"
 #include "Time.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
@@ -68,7 +67,7 @@ Foam::IOobject createIOobject
         lookupName,
         mesh.time().constant(),
         // located under finite-area
-        faMeshesRegistry::New(mesh).thisDb(),
+        faMesh::Registry(mesh),
         IOobjectOption::MUST_READ,
         IOobjectOption::NO_WRITE,
         IOobjectOption::REGISTER
@@ -188,11 +187,7 @@ Foam::fa::options& Foam::fa::options::New
     );
 
     // Registered under finite-area?
-    auto* ptr =
-        faMeshesRegistry::New(mesh).thisDb().getObjectPtr<fa::options>
-        (
-            lookupName
-        );
+    auto* ptr = faMesh::Registry(mesh).getObjectPtr<fa::options>(lookupName);
 
     if (!ptr && polyMesh::regionName(defaultAreaName).empty())
     {

src/faOptions/sources/derived/contactHeatFluxSource/contactHeatFluxSource.C

@@ -30,7 +30,6 @@ License
 #include "addToRunTimeSelectionTable.H"
 #include "volFields.H"
 #include "famSup.H"
-#include "zeroGradientFaPatchFields.H"
 
 // * * * * * * * * * * * * * Static Member Functions * * * * * * * * * * * * //
 
@@ -57,13 +56,10 @@ Foam::fa::contactHeatFluxSource::contactHeatFluxSource
 :
     fa::faceSetOption(sourceName, modelType, dict, mesh, defaultAreaName),
     TName_(dict.getOrDefault<word>("T", "T")),
-    TprimaryName_(dict.get<word>("Tprimary")),
+    TprimaryName_(dict.getOrDefault<word>("Tprimary", "T")),
     Tprimary_(mesh_.lookupObject<volScalarField>(TprimaryName_)),
-    thicknessLayers_(),
-    kappaLayers_(),
     contactRes_(0),
-    curTimeIndex_(-1),
-    coupling_()
+    curTimeIndex_(-1)
 {
     fieldNames_.resize(1, TName_);
 
@@ -131,30 +127,30 @@ void Foam::fa::contactHeatFluxSource::addSup
     const label fieldi
 )
 {
-    if (isActive())
+    if (!isActive())
     {
-        DebugInfo
-            << name() << ": applying source to "
-            << eqn.psi().name() << endl;
+        return;
+    }
 
-        if (curTimeIndex_ != mesh().time().timeIndex())
-        {
-            tmp<DimensionedField<scalar, areaMesh>> htcw(htc());
+    DebugInfo<< name() << ": applying source to " << eqn.psi().name() << endl;
 
-            // Wall temperature - mapped from primary field to finite-area
-            auto Twall = DimensionedField<scalar, areaMesh>::New
-            (
-                "Tw_" + option::name(),
-                regionMesh(),
-                dimensionedScalar(dimTemperature, Zero)
-            );
+    if (curTimeIndex_ != mesh().time().timeIndex())
+    {
+        tmp<DimensionedField<scalar, areaMesh>> htcw(htc());
 
-            vsm().mapInternalToSurface<scalar>(Tprimary_, Twall.ref().field());
+        // Wall temperature - mapped from primary field to finite-area
+        auto Twall = DimensionedField<scalar, areaMesh>::New
+        (
+            "Tw_" + option::name(),
+            regionMesh(),
+            dimensionedScalar(dimTemperature, Zero)
+        );
 
-            eqn += -fam::Sp(htcw(), eqn.psi()) + htcw()*Twall;
+        vsm().mapInternalToSurface<scalar>(Tprimary_, Twall.ref().field());
 
-            curTimeIndex_ = mesh().time().timeIndex();
-        }
+        eqn += -fam::Sp(htcw(), eqn.psi()) + htcw()*Twall;
+
+        curTimeIndex_ = mesh().time().timeIndex();
     }
 }
 
@@ -190,8 +186,14 @@ bool Foam::fa::contactHeatFluxSource::read(const dictionary& dict)
 
         const labelList& patches = regionMesh().whichPolyPatches();
 
-        coupling_.clear();
-        coupling_.resize(patches.empty() ? 0 : (patches.last()+1));
+        if (patches.empty())
+        {
+            coupling_.clear();
+        }
+        else
+        {
+            coupling_.resize_null(patches.back()+1);
+        }
 
         for (const label patchi : patches)
         {

src/faOptions/sources/derived/contactHeatFluxSource/contactHeatFluxSource.H

@@ -40,6 +40,8 @@ Usage
     {
         // Mandatory entries (unmodifiable)
         type                contactHeatFluxSource;
+
+        // Optional entries (unmodifiable)
         Tprimary            <TprimaryFieldName>;
 
         // Optional entries (runtime modifiable)
@@ -60,12 +62,19 @@ Usage
     \table
       Property  | Description                       | Type  | Reqd | Dflt
       type      | Type name: contactHeatFluxSource  | word  | yes  | -
-      Tprimary  | Name of primary temperature field | word  | yes  | -
       T         | Name of operand temperature field | word  | no   | T
+      Tprimary  | Name of primary temperature field | word  | no   | T
       thicknessLayers | List of thicknesses of layers | scalarList | no | -
       kappaLayers | List of conductivities of layers | scalarList | cndtnl | -
     \endtable
 
+    Fields/variables used:
+    \table
+      Property  | Description               | Type   | Deflt
+      T         | Temperature               | shell  | T
+      Tprimary  | Temperature               | volume | T
+    \endtable
+
     The inherited entries are elaborated in:
      - \link faOption.H \endlink
      - \link faceSetOption.H \endlink
@@ -124,13 +133,13 @@ class contactHeatFluxSource
 
     // Private Data
 
-        //- Name of temperature field
+        //- Name of shell temperature field (default: "T")
         word TName_;
 
-        //- Name of primary temperature field
-        word TprimaryName_;
+        //- Name of volume temperature field (default: "T")
+        const word TprimaryName_;
 
-        //- Primary region temperature
+        //- Primary (volume) region temperature
         const volScalarField& Tprimary_;
 
         //- Thickness of layers

src/faOptions/sources/derived/externalHeatFluxSource/externalHeatFluxSource.C

@@ -72,10 +72,6 @@ Foam::fa::externalHeatFluxSource::externalHeatFluxSource
     fa::faceSetOption(sourceName, modelType, dict, m, defaultAreaName),
     mode_(operationModeNames.get("mode", dict)),
     TName_(dict.getOrDefault<word>("T", "T")),
-    Q_(nullptr),
-    q_(nullptr),
-    h_(nullptr),
-    Ta_(nullptr),
     emissivity_(dict.getOrDefault<scalar>("emissivity", 0))
 {
     fieldNames_.resize(1, TName_);
@@ -205,6 +201,11 @@ bool Foam::fa::externalHeatFluxSource::read(const dictionary& dict)
 
         mode_ = operationModeNames.get("mode", dict);
 
+        Q_.reset(nullptr);
+        q_.reset(nullptr);
+        h_.reset(nullptr);
+        Ta_.reset(nullptr);
+
         switch (mode_)
         {
             case fixedPower:

src/faOptions/sources/derived/externalHeatFluxSource/externalHeatFluxSource.H

@@ -103,7 +103,7 @@ Usage
     \verbatim
       power       | Use fixed power (supply Q)
       flux        | Use fixed heat flux (supply q)
-      coefficient | Use fixes heat transfer coefficient (supply h and T)
+      coefficient | Use fixes heat transfer coefficient (supply h and Ta)
     \endverbatim
 
 See also
@@ -159,7 +159,7 @@ private:
         //- Operation mode
         operationMode mode_;
 
-        //- Name of temperature field
+        //- Name of shell temperature field (default: "T")
         word TName_;
 
         //- Heat power [W]
@@ -174,7 +174,7 @@ private:
         //- Ambient temperature [K]
         autoPtr<Function1<scalar>> Ta_;
 
-        //- Optional surface emissivity for radiative transfer to ambient
+        //- Surface emissivity for radiative transfer to ambient (default: 0)
         scalar emissivity_;
 
 

src/faOptions/sources/derived/jouleHeatingSource/jouleHeatingSource.H

@@ -115,23 +115,30 @@ Usage
      - \link faceSetOption.H \endlink
 
 Note
-  - \c anisotropicElectricalConductivity=true enables
-  anisotropic (tensorial) electrical conductivity.
-  - \c anisotropicElectricalConductivity=false enables
-  isotropic (scalar) electrical conductivity.
-  - The electrical conductivity can be specified using either:
-    - If the \c sigma entry is present the electrical conductivity is specified
-    as a function of temperature using a \c Function1 type.
-    - If not present the \c sigma field will be read from file.
-    - If the \c anisotropicElectricalConductivity flag is set to \c true,
-    \c sigma should be specified as a tensor quantity.
+   If the \c sigma entry is present, the electrical conductivity is specified
+   as a function of temperature using a \c Function1 type, otherwise
+   the \c sigma field will be read from file.
+   When the \c anisotropicElectricalConductivity flag is set to \c true,
+   \c sigma should be specified as a \em tensor quantity instead of as
+   an isotropic \em scalar quantity.
+
+   BREAKING Naming changes from 2056 and earlier for the fields:
+   \table
+     Field   | Scoped names              | Scoped names (old)
+     V       | \<scope\>:V (suffix)      | \<scope\>:V_ + regionName
+     sigma   | \<scope\>:sigma (suffix)  | \<scope\>:sigma_ + regionName
+   \endtable
+
+   It is possible to replicate the older naming by specifying
+   the \c suffixing to ('_' + regionName).
 
 See also
   - Foam::Function1
+  - Foam::fv::jouleHeatingSource
 
 SourceFiles
-    jouleHeatingSource.C
-    jouleHeatingSourceTemplates.C
+    jouleHeatingSource.cxx
+    jouleHeatingSourceImpl.cxx
 
 \*---------------------------------------------------------------------------*/
 
@@ -188,13 +195,13 @@ class jouleHeatingSource
         void initialiseSigma
         (
             const dictionary& dict,
-            autoPtr<Function1<Type>>& sigmaVsTPtr
+            autoPtr<Function1<Type>>& sigmaFunctionPtr
         );
 
         //- Update the electrical conductivity field
         template<class Type>
         const GeometricField<Type, faPatchField, areaMesh>&
-        updateSigma(const autoPtr<Function1<Type>>& sigmaVsTPtr) const;
+        updateSigma(const autoPtr<Function1<Type>>& sigmaFunctionPtr) const;
 
 
 public:
@@ -229,22 +236,22 @@ public:
 
     // Member Functions
 
-        // Evaluation
+    // Evaluation
 
-            //- Add explicit contribution to compressible momentum equation
-            virtual void addSup
-            (
-                const areaScalarField& h,
-                const areaScalarField& rho,
-                faMatrix<scalar>& eqn,
-                const label fieldi
-            );
+        //- Add explicit contribution to energy equation
+        virtual void addSup
+        (
+            const areaScalarField& h,
+            const areaScalarField& rho,
+            faMatrix<scalar>& eqn,
+            const label fieldi
+        );
 
 
-        // IO
+    // IO
 
-            //- Read source dictionary
-            virtual bool read(const dictionary& dict);
+        //- Read source dictionary
+        virtual bool read(const dictionary& dict);
 };
 
 
@@ -255,12 +262,6 @@ public:
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-#ifdef NoRepository
-    #include "jouleHeatingSourceTemplates.C"
-#endif
-
-// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
-
 #endif
 
 // ************************************************************************* //

src/faOptions/sources/derived/jouleHeatingSource/jouleHeatingSource.cxx

@@ -42,6 +42,12 @@ namespace fa
 }
 
 
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+// Implementation
+#include "jouleHeatingSourceImpl.cxx"
+
+
 // * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
 
 Foam::fa::jouleHeatingSource::jouleHeatingSource
@@ -59,7 +65,7 @@ Foam::fa::jouleHeatingSource::jouleHeatingSource
     (
         IOobject
         (
-            IOobject::scopedName(typeName, "V_" + regionName_),
+            suffixed(IOobject::scopedName(typeName, "V")),
             regionMesh().thisDb().time().timeName(),
             regionMesh().thisDb(),
             IOobject::MUST_READ,
@@ -68,8 +74,6 @@ Foam::fa::jouleHeatingSource::jouleHeatingSource
         ),
         regionMesh()
     ),
-    scalarSigmaVsTPtr_(nullptr),
-    tensorSigmaVsTPtr_(nullptr),
     curTimeIndex_(-1),
     nIter_(1),
     anisotropicElectricalConductivity_(false)
@@ -78,6 +82,8 @@ Foam::fa::jouleHeatingSource::jouleHeatingSource
 
     fa::option::resetApplied();
 
+    read(dict);
+
     if (anisotropicElectricalConductivity_)
     {
         Info<< "    Using tensor electrical conductivity" << endl;
@@ -90,8 +96,6 @@ Foam::fa::jouleHeatingSource::jouleHeatingSource
 
         initialiseSigma(coeffs_, scalarSigmaVsTPtr_);
     }
-
-    read(dict);
 }
 
 
@@ -105,12 +109,14 @@ void Foam::fa::jouleHeatingSource::addSup
     const label fieldi
 )
 {
-    if (isActive())
+    if (!isActive())
     {
-        DebugInfo
-            << name() << ": applying source to "
-            << eqn.psi().name() << endl;
+        return;
+    }
 
+    DebugInfo<< name() << ": applying source to " << eqn.psi().name() << endl;
+
+    {
         if (curTimeIndex_ != mesh().time().timeIndex())
         {
             for (label i = 0; i < nIter_; ++i)
@@ -118,8 +124,7 @@ void Foam::fa::jouleHeatingSource::addSup
                 if (anisotropicElectricalConductivity_)
                 {
                     // Update sigma as a function of T if required
-                    const areaTensorField& sigma =
-                        updateSigma(tensorSigmaVsTPtr_);
+                    const auto& sigma = updateSigma(tensorSigmaVsTPtr_);
 
                     // Solve the electrical potential equation
                     faScalarMatrix VEqn(fam::laplacian(h*sigma, V_));
@@ -129,8 +134,7 @@ void Foam::fa::jouleHeatingSource::addSup
                 else
                 {
                     // Update sigma as a function of T if required
-                    const areaScalarField& sigma =
-                        updateSigma(scalarSigmaVsTPtr_);
+                    const auto& sigma = updateSigma(scalarSigmaVsTPtr_);
 
                     // Solve the electrical potential equation
                     faScalarMatrix VEqn(fam::laplacian(h*sigma, V_));
@@ -145,7 +149,7 @@ void Foam::fa::jouleHeatingSource::addSup
         // Add the Joule heating contribution
         const word sigmaName
         (
-            IOobject::scopedName(typeName, "sigma_" + regionName_)
+            IOobject::scopedName(typeName, "sigma") + suffixHint()
         );
 
         areaVectorField gradV("gradV", fac::grad(V_));
@@ -162,15 +166,13 @@ void Foam::fa::jouleHeatingSource::addSup
 
         if (anisotropicElectricalConductivity_)
         {
-            const auto& sigma =
-                obr.lookupObject<areaTensorField>(sigmaName);
+            const auto& sigma = obr.lookupObject<areaTensorField>(sigmaName);
 
             tsource = (h*sigma & gradV) & gradV;
         }
         else
         {
-            const auto& sigma =
-                obr.lookupObject<areaScalarField>(sigmaName);
+            const auto& sigma = obr.lookupObject<areaScalarField>(sigmaName);
 
             tsource = (h*sigma*gradV) & gradV;
         }

src/faOptions/sources/derived/jouleHeatingSource/jouleHeatingSourceImpl.cxx

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019-2024 OpenCFD Ltd.
+    Copyright (C) 2019-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -33,16 +33,21 @@ template<class Type>
 void Foam::fa::jouleHeatingSource::initialiseSigma
 (
     const dictionary& dict,
-    autoPtr<Function1<Type>>& sigmaVsTPtr
+    autoPtr<Function1<Type>>& sigmaFunctionPtr
 )
 {
     typedef GeometricField<Type, faPatchField, areaMesh> FieldType;
 
+    const word sigmaName
+    (
+        IOobject::scopedName(typeName, "sigma") + suffixHint()
+    );
+
     auto& obr = regionMesh().thisDb();
 
     IOobject io
     (
-        IOobject::scopedName(typeName, "sigma_" + regionName_),
+        sigmaName,
         obr.time().timeName(),
         obr,
         IOobject::NO_READ,
@@ -52,11 +57,11 @@ void Foam::fa::jouleHeatingSource::initialiseSigma
 
     autoPtr<FieldType> tsigma;
 
-    if (dict.found("sigma"))
-    {
-        // Sigma to be defined using a Function1 type
-        sigmaVsTPtr = Function1<Type>::New("sigma", dict, &mesh_);
+    // Is sigma defined using a Function1 type?
+    sigmaFunctionPtr = Function1<Type>::NewIfPresent("sigma", dict, &mesh_);
 
+    if (sigmaFunctionPtr)
+    {
         tsigma.reset
         (
             new FieldType
@@ -89,31 +94,34 @@ template<class Type>
 const Foam::GeometricField<Type, Foam::faPatchField, Foam::areaMesh>&
 Foam::fa::jouleHeatingSource::updateSigma
 (
-    const autoPtr<Function1<Type>>& sigmaVsTPtr
+    const autoPtr<Function1<Type>>& sigmaFunctionPtr
 ) const
 {
     typedef GeometricField<Type, faPatchField, areaMesh> FieldType;
 
+    const word sigmaName
+    (
+        IOobject::scopedName(typeName, "sigma") + suffixHint()
+    );
+
     const auto& obr = regionMesh().thisDb();
 
-    auto& sigma =
-        obr.lookupObjectRef<FieldType>
-        (
-            IOobject::scopedName(typeName, "sigma_" + regionName_)
-        );
+    auto& sigma = obr.lookupObjectRef<FieldType>(sigmaName);
 
-    if (!sigmaVsTPtr)
+    if (!sigmaFunctionPtr)
     {
         // Electrical conductivity field, sigma, was specified by the user
         return sigma;
     }
 
+    const auto& sigmaFunction = sigmaFunctionPtr();
+
     const auto& T = obr.lookupObject<areaScalarField>(TName_);
 
     // Internal field
     forAll(sigma, i)
     {
-        sigma[i] = sigmaVsTPtr->value(T[i]);
+        sigma[i] = sigmaFunction.value(T[i]);
     }
 
 
@@ -127,7 +135,7 @@ Foam::fa::jouleHeatingSource::updateSigma
             const scalarField& Tbf = T.boundaryField()[patchi];
             forAll(pf, facei)
             {
-                pf[facei] = sigmaVsTPtr->value(Tbf[facei]);
+                pf[facei] = sigmaFunction.value(Tbf[facei]);
             }
         }
     }

src/fileFormats/ensight/file/ensightCase.H

@@ -34,7 +34,7 @@ SourceFiles
     ensightCase.C
     ensightCaseI.H
     ensightCaseOptions.C
-    ensightCaseTemplates.C
+    ensightCase.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -548,7 +548,7 @@ public:
 #include "ensightCaseI.H"
 
 #ifdef NoRepository
-    #include "ensightCaseTemplates.C"
+    #include "ensightCase.txx"
 #endif
 
 #endif

src/fileFormats/ensight/file/ensightFile.H

@@ -394,7 +394,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "ensightFileTemplates.C"
+    #include "ensightFile.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/fileFormats/ensight/output/ensightOutput.H

@@ -31,7 +31,7 @@ Description
 
 SourceFiles
     ensightOutput.C
-    ensightOutputTemplates.C
+    ensightOutput.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -557,7 +557,7 @@ bool writeFaceLocalField
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "ensightOutputTemplates.C"
+    #include "ensightOutput.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/fileFormats/ensight/part/surface/ensightOutputSurface.H

@@ -38,7 +38,7 @@ Note
 
 SourceFiles
     ensightOutputSurface.C
-    ensightOutputSurfaceTemplates.C
+    ensightOutputSurface.txx
 
 \*---------------------------------------------------------------------------*/
 
@@ -136,7 +136,7 @@ public:
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
 #ifdef NoRepository
-    #include "ensightOutputSurfaceTemplates.C"
+    #include "ensightOutputSurface.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/fileFormats/vtk/file/foamVtkFileWriter.H

@@ -42,8 +42,8 @@ Description
 
 SourceFiles
     foamVtkFileWriter.C
+    foamVtkFileWriter.txx
     foamVtkFileWriterI.H
-    foamVtkFileWriterTemplates.C
 
 \*---------------------------------------------------------------------------*/
 
@@ -350,7 +350,7 @@ public:
 #include "foamVtkFileWriterI.H"
 
 #ifdef NoRepository
-    #include "foamVtkFileWriterTemplates.C"
+    #include "foamVtkFileWriter.txx"
 #endif
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

src/fileFormats/vtk/file/foamVtkSeriesWriter.C

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2023 OpenCFD Ltd.
+    Copyright (C) 2018-2025 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -64,13 +64,17 @@ namespace Foam
     //   2. natural sort (name)
     struct seriesLess
     {
-        bool operator()(const fileNameInstant a, const fileNameInstant b) const
+        template<class StringType>
+        bool operator()
+        (
+            const Instant<StringType>& a,
+            const Instant<StringType>& b
+        ) const
         {
             scalar val = compareOp<scalar>()(a.value(), b.value());
             if (val == 0)
             {
-                return
-                    stringOps::natural_sort::compare(a.name(), b.name()) < 0;
+                return stringOps::natural_sort::less(a.name(), b.name());
             }
             return val < 0;
         }
@@ -78,7 +82,7 @@ namespace Foam
 
 
     // Check if value is less than upper, with some tolerance.
-    static inline bool lessThan(const scalar& val, const scalar& upper)
+    static inline bool lessThan(scalar val, scalar upper)
     {
         return (val < upper && Foam::mag(val - upper) > ROOTVSMALL);
     }