ENH: more fault-tolerance in makeFaMesh decomposition

- if the volume faceProcAddressing is missing, it is not readily
  possible to determine equivalent area procAddressing.

  Instead of throwing an error, be more fault-tolerant by having it
  create with READ_IF_PRESENT and then detect and warn
  if there are problems.

applications/utilities/finiteArea/makeFaMesh/decomposeFaFields.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
@@ -15,9 +15,21 @@ Description
 
 \*---------------------------------------------------------------------------*/
 
+// Embed do-while to support early termination
 if (doDecompose && Pstream::parRun())
+do
 {
-    faMeshReconstructor reconstructor(aMesh);
+    faMeshReconstructor reconstructor(aMesh, IOobjectOption::READ_IF_PRESENT);
+
+    if (!reconstructor.good())
+    {
+        Info<< "Missing volume proc-addressing, "
+               "cannot generate area proc-addressing." << nl
+            << "Also skip decomposing area fields...."
+            << endl;
+        break;
+    }
+
     reconstructor.writeAddressing();
 
     Info<< "Wrote proc-addressing" << nl << endl;
@@ -77,7 +89,7 @@ if (doDecompose && Pstream::parRun())
         areaFieldsCache.decomposeAllFields(fieldDecomposer, true);
         Info<< endl;
     }
-}
+} while (false);
 
 
 // ************************************************************************* //

src/parallel/decompose/faDecompose/faFieldDecomposer.H

@@ -402,7 +402,7 @@ class faFieldDecomposer::fieldsCache
 
         class privateCache;
 
-        //- All field and field-field types for lagrangian
+        //- All field and field-field types for finiteArea
         std::unique_ptr<privateCache> cache_;
 
 

src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C

@@ -466,7 +466,7 @@ void Foam::faMeshReconstructor::createMesh()
 
                 IOobject::NO_READ,
                 IOobject::NO_WRITE,
-                false  // not registered
+                IOobject::NO_REGISTER
             ),
             pointField(singlePatchPoints_),  // copy
             faceList(singlePatchFaces_),     // copy
@@ -525,10 +525,12 @@ void Foam::faMeshReconstructor::createMesh()
 
 Foam::faMeshReconstructor::faMeshReconstructor
 (
-    const faMesh& procMesh
+    const faMesh& procMesh,
+    IOobjectOption::readOption readVolAddressing
 )
 :
-    procMesh_(procMesh)
+    procMesh_(procMesh),
+    errors_(0)
 {
     if (!Pstream::parRun())
     {
@@ -537,32 +539,49 @@ Foam::faMeshReconstructor::faMeshReconstructor
             << exit(FatalError);
     }
 
-    // Require faceProcAddressing from finiteVolume decomposition
+    IOobject ioAddr
-    labelIOList fvFaceProcAddressing
     (
-        IOobject
+        "faceProcAddressing",
-        (
+        procMesh_.mesh().facesInstance(),
-            "faceProcAddressing",
-            procMesh_.mesh().facesInstance(),
 
-            // Or search?
+        // Or search?
-            // procMesh_.time().findInstance
+        // procMesh_.time().findInstance
-            // (
+        // (
-            //     // Search for polyMesh face instance
+        //     // Search for polyMesh face instance
-            //     // mesh.facesInstance()
+        //     // mesh.facesInstance()
-            //     procMesh_.mesh().meshDir(),
+        //     procMesh_.mesh().meshDir(),
-            //     "faceProcAddressing"
+        //     "faceProcAddressing"
-            // ),
+        // ),
 
-            polyMesh::meshSubDir,
+        polyMesh::meshSubDir,
-            procMesh_.mesh(),    // The polyMesh db
+        procMesh_.mesh(),    // The polyMesh db
-            IOobject::MUST_READ,
+
-            IOobject::NO_WRITE,
+        readVolAddressing,   // Read option
-            false  // not registered
+        IOobject::NO_WRITE,
-        )
+        IOobject::NO_REGISTER
     );
 
-    calcAddressing(fvFaceProcAddressing);
+    // Require faceProcAddressing from finiteVolume decomposition
+    labelIOList fvFaceProcAddr(ioAddr);
+
+    // Check if any/all where read.
+    // Use 'headerClassName' for checking
+    bool fileOk
+    (
+        (fvFaceProcAddr.readOpt() != IOobjectOption::NO_READ)
+     && fvFaceProcAddr.isHeaderClass<labelIOList>()
+    );
+
+    Pstream::reduceAnd(fileOk);
+
+    if (fileOk)
+    {
+        calcAddressing(fvFaceProcAddr);
+    }
+    else
+    {
+        errors_ = 1;
+    }
 }
 
 
@@ -572,7 +591,8 @@ Foam::faMeshReconstructor::faMeshReconstructor
     const labelUList& fvFaceProcAddressing
 )
 :
-    procMesh_(procMesh)
+    procMesh_(procMesh),
+    errors_(0)
 {
     if (!Pstream::parRun())
     {

src/parallel/reconstruct/faReconstruct/faMeshReconstructor.H

@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2021 OpenCFD Ltd.
+    Copyright (C) 2021-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -44,8 +44,8 @@ SourceFiles
 
 \*---------------------------------------------------------------------------*/
 
-#ifndef faMeshReconstructor_H
+#ifndef Foam_faMeshReconstructor_H
-#define faMeshReconstructor_H
+#define Foam_faMeshReconstructor_H
 
 #include "faMesh.H"
 #include "primitivePatch.H"
@@ -69,6 +69,11 @@ class faMeshReconstructor
         //- The processor-specific faMesh
         const faMesh& procMesh_;
 
+    // Flags
+
+        //- Problems encountered during construction?
+        int errors_;
+
 
     // Addressing
 
@@ -142,7 +147,12 @@ public:
     // Constructors
 
         //- Construct from components
-        explicit faMeshReconstructor(const faMesh& procMesh);
+        explicit faMeshReconstructor
+        (
+            const faMesh& procMesh,
+            IOobjectOption::readOption readVolProcAddr =
+                IOobjectOption::MUST_READ
+        );
 
         //- Construct from components
         faMeshReconstructor
@@ -160,6 +170,9 @@ public:
 
     // Member Functions
 
+        //- True if no construct errors encountered
+        bool good() const noexcept { return !errors_; }
+
         //- Processor point addressing
         const labelList& pointProcAddressing() const noexcept
         {