From 473e14418a038fa786c2ab888782458a5352ceee Mon Sep 17 00:00:00 2001
From: Mark Olesen <Mark.Olesen@esi-group.com>
Date: Tue, 23 Aug 2022 15:58:32 +0200
Subject: [PATCH] ENH: more consistent use of broadcast, combineReduce etc.

  - broadcast           : (replaces scatter)
  - combineReduce       == combineGather + broadcast
  - listCombineReduce   == listCombineGather + broadcast
  - mapCombineReduce    == mapCombineGather + broadcast
  - allGatherList       == gatherList + scatterList

  Before settling on a more consistent naming convention,
  some intermediate namings were used in OpenFOAM-v2206:

    - combineReduce       (2206: combineAllGather)
    - listCombineReduce   (2206: listCombineAllGather)
    - mapCombineReduce    (2206: mapCombineAllGather)
---
 .../test/IndirectList/Test-IndirectList.C     |  2 +-
 applications/test/Tuple2/Test-Tuple2.C        |  8 +++---
 .../Test-decomposedBlockData.C                |  2 +-
 .../test/globalIndex/Test-globalIndex.C       |  2 +-
 applications/test/minMax1/Test-minMax1.C      |  6 +---
 .../Test-parallel-communicators.C             |  2 +-
 .../Test-parallel-nonBlocking.C               |  4 +--
 .../extrudeToRegionMesh/extrudeToRegionMesh.C |  8 +++---
 .../conformalVoronoiMeshConformToSurface.C    |  4 +--
 .../generation/snappyHexMesh/snappyHexMesh.C  | 10 ++++---
 .../manipulation/checkMesh/checkTopology.C    |  6 +---
 .../manipulation/createPatch/createPatch.C    |  2 +-
 .../splitMeshRegions/splitMeshRegions.C       |  2 +-
 .../foamFormatConvert/foamFormatConvert.C     |  8 +++---
 .../parLagrangianDistributor.C                | 17 +++++------
 .../parLagrangianDistributorTemplates.C       | 11 ++------
 .../redistributePar/redistributePar.C         | 10 +++----
 .../foamToEnsight/findCloudFields.H           |  2 +-
 .../foamToVTK/convertLagrangian.H             |  6 ++--
 .../particleTracks/particleTracks.C           |  2 +-
 .../particleTracksSamplerTemplates.C          |  3 +-
 .../postChannel/channelIndexTemplates.C       |  2 +-
 .../surfaceMeshExtract/surfaceMeshExtract.C   | 28 +++++++++----------
 .../surfaceRedistributePar.C                  |  2 +-
 .../Lists/SortableList/ParSortableList.C      |  2 +-
 src/OpenFOAM/db/IOobjectList/IOobjectList.C   |  6 ++--
 .../fields/Fields/Field/FieldFunctions.C      |  8 +++---
 src/OpenFOAM/fields/Fields/Field/FieldOps.C   |  4 +--
 .../procFacesGAMGProcAgglomeration.C          |  4 +--
 .../polyMesh/globalMeshData/globalMeshData.C  |  8 +++---
 .../mapDistribute/mapDistributeBase.H         |  4 +--
 .../polyMesh/syncTools/syncToolsTemplates.C   |  4 +--
 .../globalIndexAndTransform.C                 |  4 +--
 .../primitives/random/Random/Random.C         | 26 ++++++++---------
 .../random/Random/RandomTemplates.C           | 18 ++++++------
 .../extrudePatchMesh/extrudePatchMesh.C       |  2 +-
 .../fvMeshDistribute/fvMeshDistribute.C       |  2 +-
 .../polyTopoChange/hexRef8/hexRef8.C          |  4 +--
 src/fileFormats/vtk/file/foamVtkFileWriter.H  |  2 +-
 .../faGlobalMeshData/faGlobalMeshData.C       |  2 +-
 .../turbulentDFSEMInletFvPatchVectorField.C   |  2 +-
 .../fvMesh/fvMeshSubset/fvMeshSubset.C        |  2 +-
 src/functionObjects/field/Curle/Curle.C       |  2 +-
 .../field/DMD/DMDModels/derived/STDMD/STDMD.C | 24 ++++++++--------
 .../columnAverage/columnAverageTemplates.C    |  4 +--
 .../field/externalCoupled/externalCoupled.C   |  2 +-
 .../extractEulerianParticles.C                |  4 +--
 .../regionSizeDistribution.C                  |  4 +--
 .../field/streamLine/streamLineBase.C         |  2 +-
 .../forces/propellerInfo/propellerInfo.C      |  4 +--
 .../lagrangian/vtkCloud/vtkCloudTemplates.C   |  9 ++----
 src/functionObjects/utilities/abort/abort.C   |  8 +++---
 .../utilities/areaWrite/areaWrite.C           |  2 +-
 .../utilities/areaWrite/areaWriteTemplates.C  | 12 +++-----
 .../utilities/parProfiling/parProfiling.C     |  1 -
 .../utilities/systemCall/systemCall.C         |  4 +--
 src/lagrangian/basic/Cloud/CloudIO.C          |  2 +-
 .../ParticleZoneInfo/ParticleZoneInfo.C       |  3 +-
 .../CellZoneInjection/CellZoneInjection.C     |  2 +-
 .../InflationInjection/InflationInjection.C   |  4 +--
 .../InjectedParticleDistributionInjection.C   | 17 ++++-------
 .../InjectedParticleInjection.C               | 14 ++++------
 .../PatchInjection/patchInjectionBase.C       |  2 +-
 .../clouds/Templates/SprayCloud/SprayCloudI.H |  2 +-
 .../movement/lumpedPointMovement.C            |  6 ++--
 .../meshRefinement/meshRefinement.C           |  2 +-
 .../meshRefinement/meshRefinementBaffles.C    | 10 +++----
 .../snappyHexMeshDriver/snappyRefineDriver.C  |  6 ++--
 src/meshTools/coupling/externalFileCoupler.C  | 12 ++++----
 .../mappedPolyPatch/mappedPatchBase.C         |  2 +-
 .../multiWorld/multiWorldConnectionsObject.C  |  9 ++----
 .../output/vtk/topoSet/foamVtkWriteTopoSet.H  |  8 +++---
 src/meshTools/regionSplit2D/regionSplit2D.C   |  2 +-
 .../triSurfaceMesh/triSurfaceMesh.C           |  4 +--
 .../cellSources/nearestToCell/nearestToCell.C |  2 +-
 .../faceSources/regionToFace/regionToFace.C   |  2 +-
 .../planeToFaceZone/planeToFaceZone.C         |  4 +--
 .../nearestToPoint/nearestToPoint.C           |  2 +-
 .../NURBS3DVolume/NURBS3DVolume.C             |  4 +--
 .../cellVolumeWeightCellCellStencil.C         |  4 +--
 .../inverseDistanceCellCellStencil.C          |  4 +--
 .../trackingInverseDistanceCellCellStencil.C  |  2 +-
 src/overset/regionsToCell/findRefCells.C      |  4 +--
 .../decompositionMethod/decompositionMethod.C |  4 +--
 .../multiLevelDecomp/multiLevelDecomp.C       |  8 ++----
 .../faReconstruct/faMeshReconstructor.C       | 19 +++++--------
 .../singleLayerRegion/singleLayerRegion.C     |  2 +-
 .../rigidBodyMotion/rigidBodyMotion.C         |  2 +-
 src/sampling/probes/patchProbes.C             |  2 +-
 src/sampling/probes/patchProbesTemplates.C    |  4 +--
 src/sampling/probes/probesTemplates.C         |  4 +--
 src/sampling/sampledSet/cloud/cloudSet.C      |  4 +--
 .../sampledSet/patchCloud/patchCloudSet.C     |  2 +-
 .../sampledSet/patchSeed/patchSeedSet.C       |  6 +---
 .../sampledSet/sampledSets/sampledSets.C      |  2 +-
 .../sampledSet/shortestPath/shortestPathSet.C |  2 +-
 .../sampledMeshedSurface.C                    |  2 +-
 .../sampledSurfaces/sampledSurfaces.C         |  2 +-
 .../surface/isoSurface/isoSurfacePoint.C      |  2 +-
 .../sixDoFRigidBodyMotion.C                   |  2 +-
 .../TDACChemistryModel/TDACChemistryModel.C   |  2 +-
 .../solarLoad/faceReflecting/faceReflecting.C |  4 +--
 .../radiationModels/viewFactor/viewFactor.C   | 10 ++-----
 103 files changed, 248 insertions(+), 307 deletions(-)

diff --git a/applications/test/IndirectList/Test-IndirectList.C b/applications/test/IndirectList/Test-IndirectList.C
index eb22bf3b30..399d43906c 100644
--- a/applications/test/IndirectList/Test-IndirectList.C
+++ b/applications/test/IndirectList/Test-IndirectList.C
@@ -182,7 +182,7 @@ int main(int argc, char *argv[])
 
         // MPI barrier
         bool barrier = true;
-        Pstream::scatter(barrier);
+        Pstream::broadcast(barrier);
     }
 
 
diff --git a/applications/test/Tuple2/Test-Tuple2.C b/applications/test/Tuple2/Test-Tuple2.C
index 95df0e5a42..9163f14e54 100644
--- a/applications/test/Tuple2/Test-Tuple2.C
+++ b/applications/test/Tuple2/Test-Tuple2.C
@@ -138,8 +138,8 @@ int main()
             maxFirstEqOp<label>()(maxIndexed, item);
         }
 
-        Pstream::combineAllGather(minIndexed, minFirstEqOp<label>());
-        Pstream::combineAllGather(maxIndexed, maxFirstEqOp<label>());
+        Pstream::combineReduce(minIndexed, minFirstEqOp<label>());
+        Pstream::combineReduce(maxIndexed, maxFirstEqOp<label>());
 
         Info<< "Min indexed: " << minIndexed << nl
             << "Max indexed: " << maxIndexed << nl;
@@ -156,8 +156,8 @@ int main()
             maxIndexed = maxFirstOp<label>()(maxIndexed, item);
         }
 
-        Pstream::combineAllGather(minIndexed, minFirstEqOp<label>());
-        Pstream::combineAllGather(maxIndexed, maxFirstEqOp<label>());
+        Pstream::combineReduce(minIndexed, minFirstEqOp<label>());
+        Pstream::combineReduce(maxIndexed, maxFirstEqOp<label>());
 
         Info<< "Min indexed: " << minIndexed << nl
             << "Max indexed: " << maxIndexed << nl;
diff --git a/applications/test/decomposedBlockData/Test-decomposedBlockData.C b/applications/test/decomposedBlockData/Test-decomposedBlockData.C
index 1aa698ba8e..81d62397cd 100644
--- a/applications/test/decomposedBlockData/Test-decomposedBlockData.C
+++ b/applications/test/decomposedBlockData/Test-decomposedBlockData.C
@@ -60,7 +60,7 @@ int main(int argc, char *argv[])
     Info<< "Reading " << file << nl << endl;
     decomposedBlockData data
     (
-        Pstream::worldComm,
+        UPstream::worldComm,
         IOobject
         (
             file,
diff --git a/applications/test/globalIndex/Test-globalIndex.C b/applications/test/globalIndex/Test-globalIndex.C
index c743c1316b..d1f1c851dd 100644
--- a/applications/test/globalIndex/Test-globalIndex.C
+++ b/applications/test/globalIndex/Test-globalIndex.C
@@ -204,7 +204,7 @@ int main(int argc, char *argv[])
     labelPair inOut;
     pointField allCcs(globalNumbering.gather(mesh.cellCentres()));
     inOut[0] = allCcs.size();
-    Pstream::scatter(allCcs);
+    Pstream::broadcast(allCcs);
     inOut[1] = allCcs.size();
     Pout<< "    " << inOut << endl;
 
diff --git a/applications/test/minMax1/Test-minMax1.C b/applications/test/minMax1/Test-minMax1.C
index 586b6f0384..f5b762a7fc 100644
--- a/applications/test/minMax1/Test-minMax1.C
+++ b/applications/test/minMax1/Test-minMax1.C
@@ -234,11 +234,7 @@ int main(int argc, char *argv[])
 
         Pout<< "hashed: " << hashed << nl;
 
-        Pstream::mapCombineGather
-        (
-            hashed,
-            plusEqOp<scalarMinMax>()
-        );
+        Pstream::mapCombineReduce(hashed, plusEqOp<scalarMinMax>());
 
         Info<< "reduced: " << hashed << nl;
 
diff --git a/applications/test/parallel-communicators/Test-parallel-communicators.C b/applications/test/parallel-communicators/Test-parallel-communicators.C
index 6c4662d011..635841d6fd 100644
--- a/applications/test/parallel-communicators/Test-parallel-communicators.C
+++ b/applications/test/parallel-communicators/Test-parallel-communicators.C
@@ -167,7 +167,7 @@ int main(int argc, char *argv[])
         (
             localValue,
             sumOp<scalar>(),
-            Pstream::msgType(),
+            UPstream::msgType(),
             comm
         );
         Pout<< "sum             :" << sum << endl;
diff --git a/applications/test/parallel-nonBlocking/Test-parallel-nonBlocking.C b/applications/test/parallel-nonBlocking/Test-parallel-nonBlocking.C
index a1885891d8..fc13771c73 100644
--- a/applications/test/parallel-nonBlocking/Test-parallel-nonBlocking.C
+++ b/applications/test/parallel-nonBlocking/Test-parallel-nonBlocking.C
@@ -125,13 +125,13 @@ int main(int argc, char *argv[])
     scalar data1 = 1.0;
     label request1 = -1;
     {
-        Foam::reduce(data1, sumOp<scalar>(), Pstream::msgType(), request1);
+        Foam::reduce(data1, sumOp<scalar>(), UPstream::msgType(), request1);
     }
 
     scalar data2 = 0.1;
     label request2 = -1;
     {
-        Foam::reduce(data2, sumOp<scalar>(), Pstream::msgType(), request2);
+        Foam::reduce(data2, sumOp<scalar>(), UPstream::msgType(), request2);
     }
 
 
diff --git a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
index 20b8d48da9..e6854ac097 100644
--- a/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
+++ b/applications/utilities/mesh/generation/extrude/extrudeToRegionMesh/extrudeToRegionMesh.C
@@ -661,8 +661,8 @@ void countExtrudePatches
     }
     // Synchronise decision. Actual numbers are not important, just make
     // sure that they're > 0 on all processors.
-    Pstream::listCombineAllGather(zoneSidePatch, plusEqOp<label>());
-    Pstream::listCombineAllGather(zoneZonePatch, plusEqOp<label>());
+    Pstream::listCombineReduce(zoneSidePatch, plusEqOp<label>());
+    Pstream::listCombineReduce(zoneZonePatch, plusEqOp<label>());
 }
 
 
@@ -1848,7 +1848,7 @@ int main(int argc, char *argv[])
     const primitiveFacePatch extrudePatch(std::move(zoneFaces), mesh.points());
 
 
-    Pstream::listCombineAllGather(isInternal, orEqOp<bool>());
+    Pstream::listCombineReduce(isInternal, orEqOp<bool>());
 
     // Check zone either all internal or all external faces
     checkZoneInside(mesh, zoneNames, zoneID, extrudeMeshFaces, isInternal);
@@ -2309,7 +2309,7 @@ int main(int argc, char *argv[])
         }
 
         // Reduce
-        Pstream::mapCombineAllGather(globalSum, plusEqOp<point>());
+        Pstream::mapCombineReduce(globalSum, plusEqOp<point>());
 
         forAll(localToGlobalRegion, localRegionI)
         {
diff --git a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
index 0fe385e0bd..bc1ccb10c5 100644
--- a/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
+++ b/applications/utilities/mesh/generation/foamyMesh/conformalVoronoiMesh/conformalVoronoiMesh/conformalVoronoiMeshConformToSurface.C
@@ -729,7 +729,7 @@ Foam::label Foam::conformalVoronoiMesh::synchroniseSurfaceTrees
         }
     }
 
-    Pstream::listCombineAllGather(hits, plusEqOp<labelHashSet>());
+    Pstream::listCombineReduce(hits, plusEqOp<labelHashSet>());
 
     forAll(surfaceHits, eI)
     {
@@ -816,7 +816,7 @@ Foam::label Foam::conformalVoronoiMesh::synchroniseEdgeTrees
         }
     }
 
-    Pstream::listCombineAllGather(hits, plusEqOp<labelHashSet>());
+    Pstream::listCombineReduce(hits, plusEqOp<labelHashSet>());
 
     forAll(featureEdgeHits, eI)
     {
diff --git a/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C b/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
index 508bdcb2d8..28242fdf14 100644
--- a/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
+++ b/applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C
@@ -416,10 +416,12 @@ void extractSurface
 
     // Allocate zone/patch for all patches
     HashTable<label> compactZoneID(1024);
-    forAllConstIters(patchSize, iter)
+    if (Pstream::master())
     {
-        label sz = compactZoneID.size();
-        compactZoneID.insert(iter.key(), sz);
+        forAllConstIters(patchSize, iter)
+        {
+            compactZoneID.insert(iter.key(), compactZoneID.size());
+        }
     }
     Pstream::broadcast(compactZoneID);
 
@@ -431,7 +433,7 @@ void extractSurface
         label patchi = bMesh.findPatchID(iter.key());
         if (patchi != -1)
         {
-            patchToCompactZone[patchi] = iter();
+            patchToCompactZone[patchi] = iter.val();
         }
     }
 
diff --git a/applications/utilities/mesh/manipulation/checkMesh/checkTopology.C b/applications/utilities/mesh/manipulation/checkMesh/checkTopology.C
index 82af0aa152..da07bf76ce 100644
--- a/applications/utilities/mesh/manipulation/checkMesh/checkTopology.C
+++ b/applications/utilities/mesh/manipulation/checkMesh/checkTopology.C
@@ -588,11 +588,7 @@ Foam::label Foam::checkTopology
                     }
                 }
 
-                Pstream::listCombineAllGather
-                (
-                    regionDisconnected,
-                    andEqOp<bool>()
-                );
+                Pstream::listCombineReduce(regionDisconnected, andEqOp<bool>());
             }
 
 
diff --git a/applications/utilities/mesh/manipulation/createPatch/createPatch.C b/applications/utilities/mesh/manipulation/createPatch/createPatch.C
index f15ad18ce1..0681cd9d77 100644
--- a/applications/utilities/mesh/manipulation/createPatch/createPatch.C
+++ b/applications/utilities/mesh/manipulation/createPatch/createPatch.C
@@ -714,7 +714,7 @@ void syncPoints
         }
 
         // Combine - globally consistent
-        Pstream::listCombineAllGather(sharedPts, cop);
+        Pstream::listCombineReduce(sharedPts, cop);
 
         // Now we will all have the same information. Merge it back with
         // my local information.
diff --git a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
index fd68ceb34a..4b5ceee7b7 100644
--- a/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
+++ b/applications/utilities/mesh/manipulation/splitMeshRegions/splitMeshRegions.C
@@ -1114,7 +1114,7 @@ label findCorrespondingRegion
         }
     }
 
-    Pstream::listCombineAllGather(cellsInZone, plusEqOp<label>());
+    Pstream::listCombineReduce(cellsInZone, plusEqOp<label>());
 
     // Pick region with largest overlap of zoneI
     label regionI = findMax(cellsInZone);
diff --git a/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C b/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
index 6abc6c7020..d45307c33e 100644
--- a/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
+++ b/applications/utilities/miscellaneous/foamFormatConvert/foamFormatConvert.C
@@ -223,7 +223,7 @@ bool writeOptionalMeshObject
 
     // Make sure all know if there is a valid class name
     wordList classNames(1, io.headerClassName());
-    Pstream::combineAllGather(classNames, uniqueEqOp<word>());
+    Pstream::combineReduce(classNames, uniqueEqOp<word>());
 
     // Check for correct type
     if (classNames[0] == T::typeName)
@@ -429,7 +429,7 @@ int main(int argc, char *argv[])
             )
         );
 
-        Pstream::combineAllGather(lagrangianDirs, uniqueEqOp<fileName>());
+        Pstream::combineReduce(lagrangianDirs, uniqueEqOp<fileName>());
 
         if (!lagrangianDirs.empty())
         {
@@ -466,7 +466,7 @@ int main(int argc, char *argv[])
                 )
             );
 
-            Pstream::combineAllGather(cloudDirs, uniqueEqOp<fileName>());
+            Pstream::combineReduce(cloudDirs, uniqueEqOp<fileName>());
 
             forAll(cloudDirs, i)
             {
@@ -492,7 +492,7 @@ int main(int argc, char *argv[])
                 );
 
                 // Combine with all other cloud objects
-                Pstream::combineAllGather(cloudFields, uniqueEqOp<word>());
+                Pstream::combineReduce(cloudFields, uniqueEqOp<word>());
 
                 for (const word& name : cloudFields)
                 {
diff --git a/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributor.C b/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributor.C
index 08b7977b27..ef20c1cec0 100644
--- a/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributor.C
+++ b/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributor.C
@@ -89,10 +89,11 @@ void Foam::parLagrangianDistributor::findClouds
     }
 
     // Synchronise cloud names
-    Pstream::combineGather(cloudNames, ListOps::uniqueEqOp<word>());
-    Pstream::broadcast(cloudNames);
+    Pstream::combineReduce(cloudNames, ListOps::uniqueEqOp<word>());
+    Foam::sort(cloudNames);  // Consistent order
 
-    objectNames.setSize(cloudNames.size());
+    objectNames.clear();
+    objectNames.resize(cloudNames.size());
 
     for (const fileName& localCloudName : localCloudDirs)
     {
@@ -124,11 +125,11 @@ void Foam::parLagrangianDistributor::findClouds
         }
     }
 
-    // Synchronise objectNames
-    forAll(objectNames, i)
+    // Synchronise objectNames (per cloud)
+    for (wordList& objNames : objectNames)
     {
-        Pstream::combineGather(objectNames[i], ListOps::uniqueEqOp<word>());
-        Pstream::broadcast(objectNames[i]);
+        Pstream::combineReduce(objNames, ListOps::uniqueEqOp<word>());
+        Foam::sort(objNames);  // Consistent order
     }
 }
 
@@ -291,7 +292,7 @@ Foam::parLagrangianDistributor::distributeLagrangianPositions
         nsTransPs[sendProcI] = subMap[sendProcI].size();
     }
     // Send sizes across. Note: blocks.
-    Pstream::combineAllGather(sizes, Pstream::listEq());
+    Pstream::combineReduce(sizes, Pstream::listEq());
 
     labelListList constructMap(Pstream::nProcs());
     label constructSize = 0;
diff --git a/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributorTemplates.C b/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributorTemplates.C
index a04291d961..68e13363e1 100644
--- a/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributorTemplates.C
+++ b/applications/utilities/parallelProcessing/redistributePar/parLagrangianDistributorTemplates.C
@@ -51,14 +51,9 @@ Foam::wordList Foam::parLagrangianDistributor::filterObjects
       : objects.names<Container>(selectedFields)
     );
 
-    // Parallel synchronise
-    // - Combine names from all processors
-
-    Pstream::combineGather(fieldNames, ListOps::uniqueEqOp<word>());
-    Pstream::broadcast(fieldNames);
-
-    // Sort for consistent order on all processors
-    Foam::sort(fieldNames);
+    // Parallel synchronise - combine names from all processors
+    Pstream::combineReduce(fieldNames, ListOps::uniqueEqOp<word>());
+    Foam::sort(fieldNames);  // Consistent order
 
     return fieldNames;
 }
diff --git a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
index 7afd6abd27..b5fa4d1f19 100644
--- a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
+++ b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
@@ -132,7 +132,7 @@ void createTimeDirs(const fileName& path)
         //Pstream::parRun(oldParRun);  // Restore parallel state
         masterTimeDirs = localTimeDirs;
     }
-    Pstream::scatter(masterTimeDirs);
+    Pstream::broadcast(masterTimeDirs);
     //DebugVar(masterTimeDirs);
     //DebugVar(localTimeDirs);
 
@@ -1168,7 +1168,7 @@ int main(int argc, char *argv[])
     bool nfs = true;
     {
         List<fileName> roots(1, args.rootPath());
-        Pstream::combineAllGather(roots, ListOps::uniqueEqOp<fileName>());
+        Pstream::combineReduce(roots, ListOps::uniqueEqOp<fileName>());
         nfs = (roots.size() == 1);
     }
 
@@ -1203,7 +1203,7 @@ int main(int argc, char *argv[])
         }
     }
     // If master changed to decompose mode make sure all nodes know about it
-    Pstream::scatter(decompose);
+    Pstream::broadcast(decompose);
 
 
     // If running distributed we have problem of new processors not finding
@@ -1288,7 +1288,7 @@ int main(int argc, char *argv[])
         // use the times list from the master processor
         // and select a subset based on the command-line options
         instantList timeDirs = timeSelector::select(runTime.times(), args);
-        Pstream::scatter(timeDirs);
+        Pstream::broadcast(timeDirs);
 
         if (timeDirs.empty())
         {
@@ -2067,7 +2067,7 @@ int main(int argc, char *argv[])
                 args
             )[0].value();
         }
-        Pstream::scatter(masterTime);
+        Pstream::broadcast(masterTime);
         Info<< "Setting time to that of master or undecomposed case : "
             << masterTime << endl;
         runTime.setTime(masterTime, 0);
diff --git a/applications/utilities/postProcessing/dataConversion/foamToEnsight/findCloudFields.H b/applications/utilities/postProcessing/dataConversion/foamToEnsight/findCloudFields.H
index 30adf8ed22..f761cbff79 100644
--- a/applications/utilities/postProcessing/dataConversion/foamToEnsight/findCloudFields.H
+++ b/applications/utilities/postProcessing/dataConversion/foamToEnsight/findCloudFields.H
@@ -101,7 +101,7 @@ if (timeDirs.size() && doLagrangian)
     {
         for (auto& cloudFields : regionCloudFields)
         {
-            Pstream::mapCombineAllGather
+            Pstream::mapCombineReduce
             (
                 cloudFields,
                 HashTableOps::plusEqOp<word>()
diff --git a/applications/utilities/postProcessing/dataConversion/foamToVTK/convertLagrangian.H b/applications/utilities/postProcessing/dataConversion/foamToVTK/convertLagrangian.H
index 94659d14de..f4af230525 100644
--- a/applications/utilities/postProcessing/dataConversion/foamToVTK/convertLagrangian.H
+++ b/applications/utilities/postProcessing/dataConversion/foamToVTK/convertLagrangian.H
@@ -46,11 +46,9 @@ if (doLagrangian)
     if (Pstream::parRun())
     {
         // Synchronise cloud names
-        Pstream::combineGather(cloudNames, ListOps::uniqueEqOp<word>());
-        Pstream::broadcast(cloudNames);
+        Pstream::combineReduce(cloudNames, ListOps::uniqueEqOp<word>());
     }
-    // Consistent order
-    Foam::sort(cloudNames);
+    Foam::sort(cloudNames);  // Consistent order
 
     for (const word& cloudName : cloudNames)
     {
diff --git a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
index d68800a141..edd58ceb13 100644
--- a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
+++ b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracks.C
@@ -186,7 +186,7 @@ int main(int argc, char *argv[])
         const label maxNProcs = returnReduce(maxIds.size(), maxOp<label>());
         maxIds.resize(maxNProcs, -1);
 
-        Pstream::listCombineAllGather(maxIds, maxEqOp<label>());
+        Pstream::listCombineReduce(maxIds, maxEqOp<label>());
 
         // From ids to count
         const labelList numIds = maxIds + 1;
diff --git a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracksSamplerTemplates.C b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracksSamplerTemplates.C
index d43b0eb7f7..a29b40b69a 100644
--- a/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracksSamplerTemplates.C
+++ b/applications/utilities/postProcessing/lagrangian/particleTracks/particleTracksSamplerTemplates.C
@@ -77,8 +77,7 @@ Foam::label Foam::particleTracksSampler::setTrackFields
 
         if (Pstream::parRun())
         {
-            Pstream::combineGather(fieldNames, ListOps::uniqueEqOp<word>());
-            Pstream::broadcast(fieldNames);
+            Pstream::combineReduce(fieldNames, ListOps::uniqueEqOp<word>());
         }
 
         for (const word& fieldName : fieldNames)
diff --git a/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C b/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
index 61c70dd170..e0ca2042b6 100644
--- a/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
+++ b/applications/utilities/postProcessing/miscellaneous/postChannel/channelIndexTemplates.C
@@ -40,7 +40,7 @@ Foam::Field<T> Foam::channelIndex::regionSum(const Field<T>& cellField) const
     }
 
     // Global sum
-    Pstream::listCombineAllGather(regionField, plusEqOp<T>());
+    Pstream::listCombineReduce(regionField, plusEqOp<T>());
 
     return regionField;
 }
diff --git a/applications/utilities/surface/surfaceMeshExtract/surfaceMeshExtract.C b/applications/utilities/surface/surfaceMeshExtract/surfaceMeshExtract.C
index 341566fb94..c833d486c6 100644
--- a/applications/utilities/surface/surfaceMeshExtract/surfaceMeshExtract.C
+++ b/applications/utilities/surface/surfaceMeshExtract/surfaceMeshExtract.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2017-2021 OpenCFD Ltd.
+    Copyright (C) 2017-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -302,17 +302,19 @@ int main(int argc, char *argv[])
             Pstream::mapCombineGather(patchSize, plusEqOp<label>());
             Pstream::mapCombineGather(zoneSize, plusEqOp<label>());
 
-            // Allocate compact numbering for all patches/faceZones
-            forAllConstIters(patchSize, iter)
+            if (Pstream::master())
             {
-                compactZoneID.insert(iter.key(), compactZoneID.size());
-            }
+                // Allocate compact numbering for all patches/faceZones
+                forAllConstIters(patchSize, iter)
+                {
+                    compactZoneID.insert(iter.key(), compactZoneID.size());
+                }
 
-            forAllConstIters(zoneSize, iter)
-            {
-                compactZoneID.insert(iter.key(), compactZoneID.size());
+                forAllConstIters(zoneSize, iter)
+                {
+                    compactZoneID.insert(iter.key(), compactZoneID.size());
+                }
             }
-
             Pstream::broadcast(compactZoneID);
 
 
@@ -391,13 +393,9 @@ int main(int argc, char *argv[])
         // Gather all faces
         List<faceList> gatheredFaces(Pstream::nProcs());
         gatheredFaces[Pstream::myProcNo()] = allBoundary.localFaces();
-        forAll(gatheredFaces[Pstream::myProcNo()], i)
+        for (face& f : gatheredFaces[Pstream::myProcNo()])
         {
-            inplaceRenumber
-            (
-                pointToGlobal,
-                gatheredFaces[Pstream::myProcNo()][i]
-            );
+            inplaceRenumber(pointToGlobal, f);
         }
         Pstream::gatherList(gatheredFaces);
 
diff --git a/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C b/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
index fbf65a4ffd..3b8552ea55 100644
--- a/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
+++ b/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
@@ -252,7 +252,7 @@ int main(int argc, char *argv[])
         dict.add("bounds", bbs);
 
         // Scatter patch information
-        Pstream::scatter(s.patches());
+        Pstream::broadcast(s.patches());
 
         // Construct distributedTrisurfaceMesh from components
         IOobject notReadIO(io);
diff --git a/src/OpenFOAM/containers/Lists/SortableList/ParSortableList.C b/src/OpenFOAM/containers/Lists/SortableList/ParSortableList.C
index 5e66e78be7..c6ce91be38 100644
--- a/src/OpenFOAM/containers/Lists/SortableList/ParSortableList.C
+++ b/src/OpenFOAM/containers/Lists/SortableList/ParSortableList.C
@@ -202,7 +202,7 @@ void Foam::ParSortableList<Type>::sort()
 
         getPivots(sortedPivots, pivots);
     }
-    Pstream::scatter(pivots);
+    Pstream::broadcast(pivots);
 
     if (debug)
     {
diff --git a/src/OpenFOAM/db/IOobjectList/IOobjectList.C b/src/OpenFOAM/db/IOobjectList/IOobjectList.C
index cdfd9e97da..ae82fd6246 100644
--- a/src/OpenFOAM/db/IOobjectList/IOobjectList.C
+++ b/src/OpenFOAM/db/IOobjectList/IOobjectList.C
@@ -90,12 +90,10 @@ void Foam::IOobjectList::syncNames(wordList& objNames)
     if (Pstream::parRun())
     {
         // Synchronize names
-        Pstream::combineGather(objNames, ListOps::uniqueEqOp<word>());
-        Pstream::broadcast(objNames);
+        Pstream::combineReduce(objNames, ListOps::uniqueEqOp<word>());
     }
 
-    // Consistent order on all processors
-    Foam::sort(objNames);
+    Foam::sort(objNames);  // Consistent order
 }
 
 
diff --git a/src/OpenFOAM/fields/Fields/Field/FieldFunctions.C b/src/OpenFOAM/fields/Fields/Field/FieldFunctions.C
index 9111ce62f9..00bd0cc54e 100644
--- a/src/OpenFOAM/fields/Fields/Field/FieldFunctions.C
+++ b/src/OpenFOAM/fields/Fields/Field/FieldFunctions.C
@@ -579,7 +579,7 @@ template<class Type>                                                           \
 ReturnType gFunc(const UList<Type>& f, const label comm)                       \
 {                                                                              \
     ReturnType res = Func(f);                                                  \
-    reduce(res, rFunc##Op<ReturnType>(), Pstream::msgType(), comm);            \
+    reduce(res, rFunc##Op<ReturnType>(), UPstream::msgType(), comm);           \
     return res;                                                                \
 }                                                                              \
 TMP_UNARY_FUNCTION(ReturnType, gFunc)
@@ -611,7 +611,7 @@ typename scalarProduct<Type, Type>::type gSumProd
     typedef typename scalarProduct<Type, Type>::type prodType;
 
     prodType result = sumProd(f1, f2);
-    reduce(result, sumOp<prodType>(), Pstream::msgType(), comm);
+    reduce(result, sumOp<prodType>(), UPstream::msgType(), comm);
     return result;
 }
 
@@ -624,7 +624,7 @@ Type gSumCmptProd
 )
 {
     Type SumProd = sumCmptProd(f1, f2);
-    reduce(SumProd, sumOp<Type>(), Pstream::msgType(), comm);
+    reduce(SumProd, sumOp<Type>(), UPstream::msgType(), comm);
     return SumProd;
 }
 
@@ -637,7 +637,7 @@ Type gAverage
 {
     label n = f.size();
     Type s = sum(f);
-    sumReduce(s, n, Pstream::msgType(), comm);
+    sumReduce(s, n, UPstream::msgType(), comm);
 
     if (n > 0)
     {
diff --git a/src/OpenFOAM/fields/Fields/Field/FieldOps.C b/src/OpenFOAM/fields/Fields/Field/FieldOps.C
index 4d010e9e0b..4da68f5028 100644
--- a/src/OpenFOAM/fields/Fields/Field/FieldOps.C
+++ b/src/OpenFOAM/fields/Fields/Field/FieldOps.C
@@ -172,7 +172,7 @@ Foam::Tuple2<T1,T2> Foam::FieldOps::findMinData
         result.second() = data[i];
     }
 
-    Pstream::combineAllGather(result, minFirstEqOp<T1>());
+    Pstream::combineReduce(result, minFirstEqOp<T1>());
     return result;
 }
 
@@ -193,7 +193,7 @@ Foam::Tuple2<T1,T2> Foam::FieldOps::findMaxData
         result.second() = data[i];
     }
 
-    Pstream::combineAllGather(result, maxFirstEqOp<T1>());
+    Pstream::combineReduce(result, maxFirstEqOp<T1>());
     return result;
 }
 
diff --git a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/procFacesGAMGProcAgglomeration/procFacesGAMGProcAgglomeration.C b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/procFacesGAMGProcAgglomeration/procFacesGAMGProcAgglomeration.C
index bb2fc9cd5f..2256aa117b 100644
--- a/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/procFacesGAMGProcAgglomeration/procFacesGAMGProcAgglomeration.C
+++ b/src/OpenFOAM/matrices/lduMatrix/solvers/GAMG/GAMGProcAgglomerations/procFacesGAMGProcAgglomeration/procFacesGAMGProcAgglomeration.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2013-2016 OpenFOAM Foundation
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -196,7 +196,7 @@ Foam::procFacesGAMGProcAgglomeration::processorAgglomeration
         fineToCoarse = labelUIndList(oldToNew, fineToCoarse)();
     }
 
-    Pstream::scatter(fineToCoarse, Pstream::msgType(), mesh.comm());
+    Pstream::broadcast(fineToCoarse, mesh.comm());
     UPstream::freeCommunicator(singleCellMeshComm);
 
     return tfineToCoarse;
diff --git a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
index 8627307f8d..4cd6e6f2e6 100644
--- a/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
+++ b/src/OpenFOAM/meshes/polyMesh/globalMeshData/globalMeshData.C
@@ -1934,7 +1934,7 @@ Foam::pointField Foam::globalMeshData::geometricSharedPoints() const
     pointField sharedPoints(mesh_.points(), sharedPointLabels());
 
     // Append from all processors, globally consistent
-    Pstream::combineAllGather(sharedPoints, ListOps::appendEqOp<point>());
+    Pstream::combineReduce(sharedPoints, ListOps::appendEqOp<point>());
 
     // Merge tolerance
     scalar tolDim = matchTol_ * mesh_.bounds().mag();
@@ -2730,7 +2730,7 @@ void Foam::globalMeshData::updateMesh()
     (
         mesh_.nFaces(),
         sumOp<label>(),
-        Pstream::msgType(),
+        UPstream::msgType(),
         comm
     );
 
@@ -2743,7 +2743,7 @@ void Foam::globalMeshData::updateMesh()
     (
         mesh_.nCells(),
         sumOp<label>(),
-        Pstream::msgType(),
+        UPstream::msgType(),
         comm
     );
 
@@ -2756,7 +2756,7 @@ void Foam::globalMeshData::updateMesh()
     (
         mesh_.nPoints(),
         sumOp<label>(),
-        Pstream::msgType(),
+        UPstream::msgType(),
         comm
     );
 
diff --git a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.H b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.H
index 30908213a8..a92dd574c7 100644
--- a/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.H
+++ b/src/OpenFOAM/meshes/polyMesh/mapPolyMesh/mapDistribute/mapDistributeBase.H
@@ -412,7 +412,7 @@ public:
             const globalIndex&,
             labelList& elements,
             List<Map<label>>& compactMap,
-            const int tag = Pstream::msgType(),
+            const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm
         );
 
@@ -426,7 +426,7 @@ public:
             const globalIndex&,
             labelListList& cellCells,
             List<Map<label>>& compactMap,
-            const int tag = Pstream::msgType(),
+            const int tag = UPstream::msgType(),
             const label comm = UPstream::worldComm
         );
 
diff --git a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
index b2d3e03e95..524ef8746a 100644
--- a/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
+++ b/src/OpenFOAM/meshes/polyMesh/syncTools/syncToolsTemplates.C
@@ -322,7 +322,7 @@ void Foam::syncTools::syncPointMap
             }
 
             // Broadcast: send merged values to all
-            Pstream::scatter(sharedPointValues);
+            Pstream::broadcast(sharedPointValues);
         }
 
         // Merge sharedPointValues (keyed on sharedPointAddr) into
@@ -667,7 +667,7 @@ void Foam::syncTools::syncEdgeMap
         }
 
         // Broadcast: send merged values to all
-        Pstream::scatter(sharedEdgeValues);
+        Pstream::broadcast(sharedEdgeValues);
     }
 
 
diff --git a/src/OpenFOAM/primitives/globalIndexAndTransform/globalIndexAndTransform.C b/src/OpenFOAM/primitives/globalIndexAndTransform/globalIndexAndTransform.C
index 1a763056d2..b67c2c02be 100644
--- a/src/OpenFOAM/primitives/globalIndexAndTransform/globalIndexAndTransform.C
+++ b/src/OpenFOAM/primitives/globalIndexAndTransform/globalIndexAndTransform.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -269,7 +269,7 @@ void Foam::globalIndexAndTransform::determineTransforms()
     }
 
     transforms_.transfer(localTransforms);
-    Pstream::scatter(transforms_);
+    Pstream::broadcast(transforms_);
 }
 
 
diff --git a/src/OpenFOAM/primitives/random/Random/Random.C b/src/OpenFOAM/primitives/random/Random/Random.C
index 2094b06340..73da1f7bda 100644
--- a/src/OpenFOAM/primitives/random/Random/Random.C
+++ b/src/OpenFOAM/primitives/random/Random/Random.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2017-2020 OpenCFD Ltd.
+    Copyright (C) 2017-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -143,14 +143,14 @@ Foam::label Foam::Random::position(const label& start, const label& end)
 template<>
 Foam::scalar Foam::Random::globalSample01()
 {
-    scalar value(-GREAT);
+    scalar value(0);
 
     if (Pstream::master())
     {
         value = scalar01();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -159,14 +159,14 @@ Foam::scalar Foam::Random::globalSample01()
 template<>
 Foam::label Foam::Random::globalSample01()
 {
-    label value(labelMin);
+    label value(0);
 
     if (Pstream::master())
     {
         value = round(scalar01());
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -175,14 +175,14 @@ Foam::label Foam::Random::globalSample01()
 template<>
 Foam::scalar Foam::Random::globalGaussNormal()
 {
-    scalar value(-GREAT);
+    scalar value(0);
 
     if (Pstream::master())
     {
         value = GaussNormal<scalar>();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -191,14 +191,14 @@ Foam::scalar Foam::Random::globalGaussNormal()
 template<>
 Foam::label Foam::Random::globalGaussNormal()
 {
-    label value(labelMin);
+    label value(0);
 
     if (Pstream::master())
     {
         value = GaussNormal<label>();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -211,14 +211,14 @@ Foam::scalar Foam::Random::globalPosition
     const scalar& end
 )
 {
-    scalar value(-GREAT);
+    scalar value(0);
 
     if (Pstream::master())
     {
         value = position<scalar>(start, end);
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -231,14 +231,14 @@ Foam::label Foam::Random::globalPosition
     const label& end
 )
 {
-    label value(labelMin);
+    label value(0);
 
     if (Pstream::master())
     {
         value = position<label>(start, end);
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
diff --git a/src/OpenFOAM/primitives/random/Random/RandomTemplates.C b/src/OpenFOAM/primitives/random/Random/RandomTemplates.C
index de1379170d..ab4d0ed55d 100644
--- a/src/OpenFOAM/primitives/random/Random/RandomTemplates.C
+++ b/src/OpenFOAM/primitives/random/Random/RandomTemplates.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
-    Copyright (C) 2018 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -92,14 +92,14 @@ void Foam::Random::shuffle(UList<Type>& values)
 template<class Type>
 Type Foam::Random::globalSample01()
 {
-    Type value = -GREAT*pTraits<Type>::one;
+    Type value(Zero);
 
     if (Pstream::master())
     {
         value = sample01<Type>();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -108,14 +108,14 @@ Type Foam::Random::globalSample01()
 template<class Type>
 Type Foam::Random::globalGaussNormal()
 {
-    Type value = -GREAT*pTraits<Type>::one;
+    Type value(Zero);
 
     if (Pstream::master())
     {
         value = GaussNormal<Type>();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -124,14 +124,14 @@ Type Foam::Random::globalGaussNormal()
 template<class Type>
 Type Foam::Random::globalPosition(const Type& start, const Type& end)
 {
-    Type value = -GREAT*pTraits<Type>::one;
+    Type value(Zero);
 
     if (Pstream::master())
     {
         value = position<Type>(start, end);
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 
     return value;
 }
@@ -140,14 +140,12 @@ Type Foam::Random::globalPosition(const Type& start, const Type& end)
 template<class Type>
 void Foam::Random::globalRandomise01(Type& value)
 {
-    value = -GREAT*pTraits<Type>::one;
-
     if (Pstream::master())
     {
         value = sample01<Type>();
     }
 
-    Pstream::scatter(value);
+    Pstream::broadcast(value);
 }
 
 
diff --git a/src/dynamicMesh/extrudePatchMesh/extrudePatchMesh.C b/src/dynamicMesh/extrudePatchMesh/extrudePatchMesh.C
index a0b06807e0..58b5657bd1 100644
--- a/src/dynamicMesh/extrudePatchMesh/extrudePatchMesh.C
+++ b/src/dynamicMesh/extrudePatchMesh/extrudePatchMesh.C
@@ -228,7 +228,7 @@ void Foam::extrudePatchMesh::extrudeMesh(polyPatchList& regionPatches)
             }
 
             // Reduce
-            Pstream::mapCombineAllGather(globalSum, plusEqOp<point>());
+            Pstream::mapCombineReduce(globalSum, plusEqOp<point>());
 
             forAll(localToGlobalRegion, localRegionI)
             {
diff --git a/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C b/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
index fd8416cd2a..5751e519c3 100644
--- a/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
+++ b/src/dynamicMesh/fvMeshDistribute/fvMeshDistribute.C
@@ -216,7 +216,7 @@ Foam::wordList Foam::fvMeshDistribute::mergeWordList(const wordList& procNames)
             }
         }
     }
-    Pstream::scatter(mergedNames);
+    Pstream::broadcast(mergedNames);
 
     return mergedNames;
 }
diff --git a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
index 1073465ab1..512fbcb8b5 100644
--- a/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
+++ b/src/dynamicMesh/polyTopoChange/polyTopoChange/hexRef8/hexRef8.C
@@ -436,7 +436,7 @@ Foam::scalar Foam::hexRef8::getLevel0EdgeLength() const
 
     // Get the minimum per level over all processors. Note minimum so if
     // cells are not cubic we use the smallest edge side.
-    Pstream::listCombineAllGather(typEdgeLenSqr, minEqOp<scalar>());
+    Pstream::listCombineReduce(typEdgeLenSqr, minEqOp<scalar>());
 
     if (debug)
     {
@@ -470,7 +470,7 @@ Foam::scalar Foam::hexRef8::getLevel0EdgeLength() const
         }
     }
 
-    Pstream::listCombineAllGather(maxEdgeLenSqr, maxEqOp<scalar>());
+    Pstream::listCombineReduce(maxEdgeLenSqr, maxEqOp<scalar>());
 
     if (debug)
     {
diff --git a/src/fileFormats/vtk/file/foamVtkFileWriter.H b/src/fileFormats/vtk/file/foamVtkFileWriter.H
index 248b6a9004..98f4793950 100644
--- a/src/fileFormats/vtk/file/foamVtkFileWriter.H
+++ b/src/fileFormats/vtk/file/foamVtkFileWriter.H
@@ -263,7 +263,7 @@ public:
         virtual bool open
         (
             const fileName& file,
-            bool parallel = Pstream::parRun()
+            bool parallel = UPstream::parRun()
         );
 
         //- End the file contents and close the file after writing.
diff --git a/src/finiteArea/faMesh/faGlobalMeshData/faGlobalMeshData.C b/src/finiteArea/faMesh/faGlobalMeshData/faGlobalMeshData.C
index 0c8e68f8f4..d83324d1b0 100644
--- a/src/finiteArea/faMesh/faGlobalMeshData/faGlobalMeshData.C
+++ b/src/finiteArea/faMesh/faGlobalMeshData/faGlobalMeshData.C
@@ -118,7 +118,7 @@ void Foam::faGlobalMeshData::updateMesh()
 
     sharedPointLabels_ = sharedPointLabels.toc();
 
-    Pstream::combineAllGather(globalList, plusEqOp<labelField>());
+    Pstream::combineReduce(globalList, plusEqOp<labelField>());
 
     nGlobalPoints_ = 0;
     for (label i=0; i<globalList.size(); ++i)
diff --git a/src/finiteVolume/fields/fvPatchFields/derived/turbulentDFSEMInlet/turbulentDFSEMInletFvPatchVectorField.C b/src/finiteVolume/fields/fvPatchFields/derived/turbulentDFSEMInlet/turbulentDFSEMInletFvPatchVectorField.C
index 4c36356947..b31a781d3a 100644
--- a/src/finiteVolume/fields/fvPatchFields/derived/turbulentDFSEMInlet/turbulentDFSEMInletFvPatchVectorField.C
+++ b/src/finiteVolume/fields/fvPatchFields/derived/turbulentDFSEMInlet/turbulentDFSEMInletFvPatchVectorField.C
@@ -164,7 +164,7 @@ void Foam::turbulentDFSEMInletFvPatchVectorField::initialisePatch()
     sumTriMagSf_ = Zero;
     sumTriMagSf_[Pstream::myProcNo() + 1] = sum(triMagSf);
 
-    Pstream::listCombineAllGather(sumTriMagSf_, maxEqOp<scalar>());
+    Pstream::listCombineReduce(sumTriMagSf_, maxEqOp<scalar>());
 
     for (label i = 1; i < triMagSf.size(); ++i)
     {
diff --git a/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C b/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
index 308a553009..3dba1abcd6 100644
--- a/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
+++ b/src/finiteVolume/fvMesh/fvMeshSubset/fvMeshSubset.C
@@ -1042,7 +1042,7 @@ void Foam::fvMeshSubset::reset
         // Get patch sizes (up to nextPatchID).
         // Note that up to nextPatchID the globalPatchMap is an identity so
         // no need to index through that.
-        Pstream::listCombineAllGather(globalPatchSizes, plusEqOp<label>());
+        Pstream::listCombineReduce(globalPatchSizes, plusEqOp<label>());
 
         // Now all processors have all the patchnames.
         // Decide: if all processors have the same patch names and size is zero
diff --git a/src/functionObjects/field/Curle/Curle.C b/src/functionObjects/field/Curle/Curle.C
index a03bf0fd93..813d976130 100644
--- a/src/functionObjects/field/Curle/Curle.C
+++ b/src/functionObjects/field/Curle/Curle.C
@@ -223,7 +223,7 @@ bool Foam::functionObjects::Curle::execute()
 
     pDash /= 4*mathematical::pi;
 
-    Pstream::listCombineAllGather(pDash, plusEqOp<scalar>());
+    Pstream::listCombineReduce(pDash, plusEqOp<scalar>());
 
     if (surfaceWriterPtr_)
     {
diff --git a/src/functionObjects/field/DMD/DMDModels/derived/STDMD/STDMD.C b/src/functionObjects/field/DMD/DMDModels/derived/STDMD/STDMD.C
index 2ef2efe23e..206f7025d0 100644
--- a/src/functionObjects/field/DMD/DMDModels/derived/STDMD/STDMD.C
+++ b/src/functionObjects/field/DMD/DMDModels/derived/STDMD/STDMD.C
@@ -188,8 +188,8 @@ void Foam::DMDModels::STDMD::compress()
             q.subColumn(i) = EVecs.subColumn(permutation[i]);
         }
     }
-    Pstream::scatter(G_);
-    Pstream::scatter(q);
+    Pstream::broadcast(G_);
+    Pstream::broadcast(q);
 
     // Update "Q"
     Q_ = Q_*q;
@@ -357,8 +357,8 @@ reducedKoopmanOperator()
             A1 = RxInv_*RMatrix(MatrixTools::pinv(Rx*(G_^Rx)));
             Rx.clear();
         }
-        Pstream::scatter(RxInv_);
-        Pstream::scatter(A1);
+        Pstream::broadcast(RxInv_);
+        Pstream::broadcast(A1);
 
         Info<< tab << "Computing A2" << endl;
         SMatrix A2(Qupper_ & Qlower_);
@@ -452,15 +452,15 @@ bool Foam::DMDModels::STDMD::eigendecomposition(SMatrix& Atilde)
             evals_ = cp;
         }
     }
-    Pstream::scatter(fail);
+    Pstream::broadcast(fail);
 
     if (fail)
     {
         return false;
     }
 
-    Pstream::scatter(evals_);
-    Pstream::scatter(evecs_);
+    Pstream::broadcast(evals_);
+    Pstream::broadcast(evecs_);
 
     return true;
 }
@@ -503,8 +503,8 @@ void Foam::DMDModels::STDMD::frequencies()
             it = std::find_if(std::next(it), freqs_.cend(), margin);
         }
     }
-    Pstream::scatter(freqs_);
-    Pstream::scatter(freqsi_);
+    Pstream::broadcast(freqs_);
+    Pstream::broadcast(freqsi_);
 }
 
 
@@ -567,7 +567,7 @@ void Foam::DMDModels::STDMD::amplitudes()
             }
         }
     }
-    Pstream::scatter(amps_);
+    Pstream::broadcast(amps_);
 }
 
 
@@ -648,8 +648,8 @@ void Foam::DMDModels::STDMD::magnitudes()
 
         std::sort(magsi_.begin(), magsi_.end(), descend);
     }
-    Pstream::scatter(mags_);
-    Pstream::scatter(magsi_);
+    Pstream::broadcast(mags_);
+    Pstream::broadcast(magsi_);
 }
 
 
diff --git a/src/functionObjects/field/columnAverage/columnAverageTemplates.C b/src/functionObjects/field/columnAverage/columnAverageTemplates.C
index 50d40abe8f..ab95a2b48f 100644
--- a/src/functionObjects/field/columnAverage/columnAverageTemplates.C
+++ b/src/functionObjects/field/columnAverage/columnAverageTemplates.C
@@ -87,8 +87,8 @@ bool Foam::functionObjects::columnAverage::columnAverageField
         }
 
         // Global sum
-        Pstream::listCombineAllGather(regionField, plusEqOp<Type>());
-        Pstream::listCombineAllGather(regionCount, plusEqOp<label>());
+        Pstream::listCombineReduce(regionField, plusEqOp<Type>());
+        Pstream::listCombineReduce(regionCount, plusEqOp<label>());
 
         forAll(regionField, regioni)
         {
diff --git a/src/functionObjects/field/externalCoupled/externalCoupled.C b/src/functionObjects/field/externalCoupled/externalCoupled.C
index 0feb198e42..4b45fb5df1 100644
--- a/src/functionObjects/field/externalCoupled/externalCoupled.C
+++ b/src/functionObjects/field/externalCoupled/externalCoupled.C
@@ -430,7 +430,7 @@ void Foam::functionObjects::externalCoupled::initCoupling()
                  || isFile(dir/"patchFaces");
             }
 
-            Pstream::scatter(geomExists);
+            Pstream::broadcast(geomExists);
 
             if (!geomExists)
             {
diff --git a/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C b/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
index b97268833d..d0ae95a792 100644
--- a/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
+++ b/src/functionObjects/field/extractEulerianParticles/extractEulerianParticles/extractEulerianParticles.C
@@ -333,7 +333,7 @@ void Foam::functionObjects::extractEulerianParticles::calculateAddressing
 
     // Create map from new regions to slots in particles list
     // - filter through new-to-new addressing to identify new particles
-    Pstream::listCombineAllGather(newToNewRegion, maxEqOp<label>());
+    Pstream::listCombineReduce(newToNewRegion, maxEqOp<label>());
 
     label nParticle = -1;
     labelHashSet newRegions;
@@ -352,7 +352,7 @@ void Foam::functionObjects::extractEulerianParticles::calculateAddressing
 
     // Accumulate old region data or create a new particle if there is no
     // mapping from the old-to-new region
-    Pstream::listCombineAllGather(oldToNewRegion, maxEqOp<label>());
+    Pstream::listCombineReduce(oldToNewRegion, maxEqOp<label>());
 
     List<eulerianParticle> newParticles(newRegionToParticleMap.size());
     forAll(oldToNewRegion, oldRegioni)
diff --git a/src/functionObjects/field/regionSizeDistribution/regionSizeDistribution.C b/src/functionObjects/field/regionSizeDistribution/regionSizeDistribution.C
index 3292d9e2af..eac6555f3d 100644
--- a/src/functionObjects/field/regionSizeDistribution/regionSizeDistribution.C
+++ b/src/functionObjects/field/regionSizeDistribution/regionSizeDistribution.C
@@ -66,7 +66,7 @@ static Map<Type> regionSum(const regionSplit& regions, const Field<Type>& fld)
         regionToSum(regioni, Type(Zero)) += fld[celli];
     }
 
-    Pstream::mapCombineAllGather(regionToSum, plusEqOp<Type>());
+    Pstream::mapCombineReduce(regionToSum, plusEqOp<Type>());
 
     return regionToSum;
 }
@@ -214,7 +214,7 @@ Foam::functionObjects::regionSizeDistribution::findPatchRegions
 
 
     // Make sure all the processors have the same set of regions
-    Pstream::mapCombineAllGather(patchRegions, minEqOp<label>());
+    Pstream::mapCombineReduce(patchRegions, minEqOp<label>());
 
     return patchRegions;
 }
diff --git a/src/functionObjects/field/streamLine/streamLineBase.C b/src/functionObjects/field/streamLine/streamLineBase.C
index d29e436313..71a476e83a 100644
--- a/src/functionObjects/field/streamLine/streamLineBase.C
+++ b/src/functionObjects/field/streamLine/streamLineBase.C
@@ -800,7 +800,7 @@ bool Foam::functionObjects::streamLineBase::writeToFile()
 
 
     // File names generated on the master but setProperty needed everywher
-    Pstream::scatter(outputFileNames);
+    Pstream::broadcast(outputFileNames);
 
     forAllConstIters(outputFileNames, iter)
     {
diff --git a/src/functionObjects/forces/propellerInfo/propellerInfo.C b/src/functionObjects/forces/propellerInfo/propellerInfo.C
index b7d3d5d660..96f120b79f 100644
--- a/src/functionObjects/forces/propellerInfo/propellerInfo.C
+++ b/src/functionObjects/forces/propellerInfo/propellerInfo.C
@@ -470,7 +470,7 @@ void Foam::functionObjects::propellerInfo::updateSampleDiskCells()
         }
     }
 
-    Pstream::listCombineAllGather(pointMask_, orEqOp<bool>());
+    Pstream::listCombineReduce(pointMask_, orEqOp<bool>());
 }
 
 
@@ -785,7 +785,7 @@ Foam::tmp<Foam::Field<Type>> Foam::functionObjects::propellerInfo::interpolate
         }
     }
 
-    Pstream::listCombineAllGather(field, maxEqOp<Type>());
+    Pstream::listCombineReduce(field, maxEqOp<Type>());
 
     return tfield;
 }
diff --git a/src/functionObjects/lagrangian/vtkCloud/vtkCloudTemplates.C b/src/functionObjects/lagrangian/vtkCloud/vtkCloudTemplates.C
index 0917da8c46..c28bc1fe4c 100644
--- a/src/functionObjects/lagrangian/vtkCloud/vtkCloudTemplates.C
+++ b/src/functionObjects/lagrangian/vtkCloud/vtkCloudTemplates.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2018-2021 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -56,11 +56,8 @@ Foam::wordList Foam::functionObjects::vtkCloud::writeFields
     // Thus need to resolve names between all processors.
 
     wordList fieldNames(obrTmp.names<IOField<Type>>());
-    Pstream::combineGather(fieldNames, ListOps::uniqueEqOp<word>());
-    Pstream::broadcast(fieldNames);
-
-    // Consistent order on all processors
-    Foam::sort(fieldNames);
+    Pstream::combineReduce(fieldNames, ListOps::uniqueEqOp<word>());
+    Foam::sort(fieldNames);  // Consistent order
 
     for (const word& fieldName : fieldNames)
     {
diff --git a/src/functionObjects/utilities/abort/abort.C b/src/functionObjects/utilities/abort/abort.C
index c8a8e0d531..639072e7d8 100644
--- a/src/functionObjects/utilities/abort/abort.C
+++ b/src/functionObjects/utilities/abort/abort.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2016-2021 OpenCFD Ltd.
+    Copyright (C) 2016-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -218,9 +218,9 @@ bool Foam::functionObjects::abort::execute()
             }
         }
 
-        // Send to slaves. Also acts as an MPI barrier
-        label intAction(action);
-        Pstream::scatter(intAction);
+        // Send to sub-ranks. Also acts as an MPI barrier
+        int intAction(action);
+        Pstream::broadcast(intAction);
 
         action = Time::stopAtControls(intAction);
 
diff --git a/src/functionObjects/utilities/areaWrite/areaWrite.C b/src/functionObjects/utilities/areaWrite/areaWrite.C
index d352615f70..1d82cf271c 100644
--- a/src/functionObjects/utilities/areaWrite/areaWrite.C
+++ b/src/functionObjects/utilities/areaWrite/areaWrite.C
@@ -267,7 +267,7 @@ bool Foam::areaWrite::write()
         }
 
         // Parallel consistency (no-op in serial)
-        Pstream::mapCombineAllGather(selected, HashSetOps::plusEqOp<word>());
+        Pstream::mapCombineReduce(selected, HashSetOps::plusEqOp<word>());
 
         missed.clear();
 
diff --git a/src/functionObjects/utilities/areaWrite/areaWriteTemplates.C b/src/functionObjects/utilities/areaWrite/areaWriteTemplates.C
index b68d656a35..ebb1ce3cc6 100644
--- a/src/functionObjects/utilities/areaWrite/areaWriteTemplates.C
+++ b/src/functionObjects/utilities/areaWrite/areaWriteTemplates.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2019-2021 OpenCFD Ltd.
+    Copyright (C) 2019-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -73,16 +73,12 @@ void Foam::areaWrite::performAction
     {
         fieldNames = areaMesh.thisDb().names<GeoField>(fieldSelection_);
 
-        // With syncPar
+        // Synchronize names
         if (Pstream::parRun())
         {
-            // Synchronize names
-            Pstream::combineGather(fieldNames, ListOps::uniqueEqOp<word>());
-            Pstream::broadcast(fieldNames);
+            Pstream::combineReduce(fieldNames, ListOps::uniqueEqOp<word>());
         }
-
-        // Sort for consistent order on all processors
-        Foam::sort(fieldNames);
+        Foam::sort(fieldNames);  // Consistent order
     }
 
     for (const word& fieldName : fieldNames)
diff --git a/src/functionObjects/utilities/parProfiling/parProfiling.C b/src/functionObjects/utilities/parProfiling/parProfiling.C
index d144dff1f0..3ba33caf6e 100644
--- a/src/functionObjects/utilities/parProfiling/parProfiling.C
+++ b/src/functionObjects/utilities/parProfiling/parProfiling.C
@@ -27,7 +27,6 @@ License
 
 #include "parProfiling.H"
 #include "addToRunTimeSelectionTable.H"
-#include "UPstream.H"
 #include "Pstream.H"
 #include "PstreamReduceOps.H"
 #include "profilingPstream.H"
diff --git a/src/functionObjects/utilities/systemCall/systemCall.C b/src/functionObjects/utilities/systemCall/systemCall.C
index 1538f38735..f5252fa98a 100644
--- a/src/functionObjects/utilities/systemCall/systemCall.C
+++ b/src/functionObjects/utilities/systemCall/systemCall.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2018-2020 OpenCFD Ltd.
+    Copyright (C) 2018-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -73,7 +73,7 @@ Foam::label Foam::functionObjects::systemCall::dispatch(const stringList& calls)
     // MPI barrier
     if (masterOnly_)
     {
-        Pstream::scatter(nCalls);
+        Pstream::broadcast(nCalls);
     }
 
     return nCalls;
diff --git a/src/lagrangian/basic/Cloud/CloudIO.C b/src/lagrangian/basic/Cloud/CloudIO.C
index 993fef90f1..d9eed02792 100644
--- a/src/lagrangian/basic/Cloud/CloudIO.C
+++ b/src/lagrangian/basic/Cloud/CloudIO.C
@@ -104,7 +104,7 @@ void Foam::Cloud<ParticleType>::writeCloudUniformProperties() const
     labelList np(Pstream::nProcs(), Zero);
     np[Pstream::myProcNo()] = ParticleType::particleCount_;
 
-    Pstream::listCombineAllGather(np, maxEqOp<label>());
+    Pstream::listCombineReduce(np, maxEqOp<label>());
 
     uniformPropsDict.add
     (
diff --git a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
index 5f3c92bb17..d01800976c 100644
--- a/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
+++ b/src/lagrangian/intermediate/submodels/CloudFunctionObjects/ParticleZoneInfo/ParticleZoneInfo.C
@@ -361,8 +361,7 @@ void Foam::ParticleZoneInfo<CloudType>::write()
     {
         // Find number of particles per proc
         labelList allMaxIDs(maxIDs_);
-        Pstream::listCombineGather(allMaxIDs, maxEqOp<label>());
-        Pstream::broadcast(allMaxIDs);
+        Pstream::listCombineReduce(allMaxIDs, maxEqOp<label>());
 
         // Combine into single list
         label n = returnReduce(data_.size(), sumOp<label>());
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
index cade4faea9..4993effd61 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/CellZoneInjection/CellZoneInjection.C
@@ -120,7 +120,7 @@ void Foam::CellZoneInjection<CloudType>::setPositions
         globalPositions.localStart(Pstream::myProcNo())
     ) = positions;
 
-    Pstream::listCombineAllGather(allPositions, minEqOp<point>());
+    Pstream::listCombineReduce(allPositions, minEqOp<point>());
 
     // Gather local cell tet and tet-point Ids, but leave non-local ids set -1
     SubList<label>
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InflationInjection/InflationInjection.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InflationInjection/InflationInjection.C
index 227aefcf5f..d65aa96c97 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InflationInjection/InflationInjection.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InflationInjection/InflationInjection.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -417,7 +417,7 @@ Foam::label Foam::InflationInjection<CloudType>::parcelsToInject
             newParticles_ = combinedNewParticles;
         }
 
-        Pstream::scatter(newParticles_);
+        Pstream::broadcast(newParticles_);
     }
 
     return newParticles_.size();
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleDistributionInjection/InjectedParticleDistributionInjection.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleDistributionInjection/InjectedParticleDistributionInjection.C
index 5dadeb83e6..d033f433eb 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleDistributionInjection/InjectedParticleDistributionInjection.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleDistributionInjection/InjectedParticleDistributionInjection.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -62,8 +62,7 @@ void Foam::InjectedParticleDistributionInjection<CloudType>::initialise()
     {
         List<List<label>> procTag(Pstream::nProcs());
         procTag[Pstream::myProcNo()].transfer(tag);
-        Pstream::gatherList(procTag);
-        Pstream::scatterList(procTag);
+        Pstream::allGatherList(procTag);
         tag =
             ListListOps::combine<List<label>>
             (
@@ -72,8 +71,7 @@ void Foam::InjectedParticleDistributionInjection<CloudType>::initialise()
 
         List<List<point>> procPosition(Pstream::nProcs());
         procPosition[Pstream::myProcNo()].transfer(position);
-        Pstream::gatherList(procPosition);
-        Pstream::scatterList(procPosition);
+        Pstream::allGatherList(procPosition);
         position =
             ListListOps::combine<List<point>>
             (
@@ -82,8 +80,7 @@ void Foam::InjectedParticleDistributionInjection<CloudType>::initialise()
 
         List<List<vector>> procU(Pstream::nProcs());
         procU[Pstream::myProcNo()].transfer(U);
-        Pstream::gatherList(procU);
-        Pstream::scatterList(procU);
+        Pstream::allGatherList(procU);
         U =
             ListListOps::combine<List<vector>>
             (
@@ -92,8 +89,7 @@ void Foam::InjectedParticleDistributionInjection<CloudType>::initialise()
 
         List<List<scalar>> procSOI(Pstream::nProcs());
         procSOI[Pstream::myProcNo()].transfer(soi);
-        Pstream::gatherList(procSOI);
-        Pstream::scatterList(procSOI);
+        Pstream::allGatherList(procSOI);
         soi =
             ListListOps::combine<List<scalar>>
             (
@@ -102,8 +98,7 @@ void Foam::InjectedParticleDistributionInjection<CloudType>::initialise()
 
         List<List<scalar>> procD(Pstream::nProcs());
         procD[Pstream::myProcNo()].transfer(d);
-        Pstream::gatherList(procD);
-        Pstream::scatterList(procD);
+        Pstream::allGatherList(procD);
         d =
             ListListOps::combine<List<scalar>>
             (
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleInjection/InjectedParticleInjection.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleInjection/InjectedParticleInjection.C
index 1057ea9cd2..9e8b6597e4 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleInjection/InjectedParticleInjection.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/InjectedParticleInjection/InjectedParticleInjection.C
@@ -5,7 +5,7 @@
     \\  /    A nd           | www.openfoam.com
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -62,8 +62,7 @@ void Foam::InjectedParticleInjection<CloudType>::initialise()
     {
         List<List<scalar>> procTime(Pstream::nProcs());
         procTime[Pstream::myProcNo()].transfer(time);
-        Pstream::gatherList(procTime);
-        Pstream::scatterList(procTime);
+        Pstream::allGatherList(procTime);
         time =
             ListListOps::combine<List<scalar>>
             (
@@ -72,8 +71,7 @@ void Foam::InjectedParticleInjection<CloudType>::initialise()
 
         List<List<point>> procPosition(Pstream::nProcs());
         procPosition[Pstream::myProcNo()].transfer(position);
-        Pstream::gatherList(procPosition);
-        Pstream::scatterList(procPosition);
+        Pstream::allGatherList(procPosition);
         position =
             ListListOps::combine<List<point>>
             (
@@ -82,8 +80,7 @@ void Foam::InjectedParticleInjection<CloudType>::initialise()
 
         List<List<scalar>> procD(Pstream::nProcs());
         procD[Pstream::myProcNo()].transfer(diameter);
-        Pstream::gatherList(procD);
-        Pstream::scatterList(procD);
+        Pstream::allGatherList(procD);
         diameter =
             ListListOps::combine<List<scalar>>
             (
@@ -92,8 +89,7 @@ void Foam::InjectedParticleInjection<CloudType>::initialise()
 
         List<List<vector>> procU(Pstream::nProcs());
         procU[Pstream::myProcNo()].transfer(U);
-        Pstream::gatherList(procU);
-        Pstream::scatterList(procU);
+        Pstream::allGatherList(procU);
         U =
             ListListOps::combine<List<vector>>
             (
diff --git a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/PatchInjection/patchInjectionBase.C b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/PatchInjection/patchInjectionBase.C
index 2f5043d418..36b5a7d874 100644
--- a/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/PatchInjection/patchInjectionBase.C
+++ b/src/lagrangian/intermediate/submodels/Kinematic/InjectionModel/PatchInjection/patchInjectionBase.C
@@ -114,7 +114,7 @@ void Foam::patchInjectionBase::updateMesh(const polyMesh& mesh)
     sumTriMagSf_ = Zero;
     sumTriMagSf_[Pstream::myProcNo() + 1] = sum(triMagSf);
 
-    Pstream::listCombineAllGather(sumTriMagSf_, maxEqOp<scalar>());
+    Pstream::listCombineReduce(sumTriMagSf_, maxEqOp<scalar>());
 
     for (label i = 1; i < triMagSf.size(); i++)
     {
diff --git a/src/lagrangian/spray/clouds/Templates/SprayCloud/SprayCloudI.H b/src/lagrangian/spray/clouds/Templates/SprayCloud/SprayCloudI.H
index 4ce6c576bc..8e2a817dab 100644
--- a/src/lagrangian/spray/clouds/Templates/SprayCloud/SprayCloudI.H
+++ b/src/lagrangian/spray/clouds/Templates/SprayCloud/SprayCloudI.H
@@ -181,7 +181,7 @@ inline Foam::scalar Foam::SprayCloud<CloudType>::penetration
         }
     }
 
-    Pstream::scatter(distance);
+    Pstream::broadcast(distance);
 
     return distance;
 }
diff --git a/src/lumpedPointMotion/movement/lumpedPointMovement.C b/src/lumpedPointMotion/movement/lumpedPointMovement.C
index 5a5d28929a..dcfc841ad2 100644
--- a/src/lumpedPointMotion/movement/lumpedPointMovement.C
+++ b/src/lumpedPointMotion/movement/lumpedPointMovement.C
@@ -880,7 +880,7 @@ Foam::List<Foam::scalar> Foam::lumpedPointMovement::areas
         }
     }
 
-    Pstream::listCombineAllGather(zoneAreas, plusEqOp<scalar>());
+    Pstream::listCombineReduce(zoneAreas, plusEqOp<scalar>());
 
     return zoneAreas;
 }
@@ -1008,8 +1008,8 @@ bool Foam::lumpedPointMovement::forcesAndMoments
         Info<<"No pressure field" << endl;
     }
 
-    Pstream::listCombineAllGather(forces, plusEqOp<vector>());
-    Pstream::listCombineAllGather(moments, plusEqOp<vector>());
+    Pstream::listCombineReduce(forces, plusEqOp<vector>());
+    Pstream::listCombineReduce(moments, plusEqOp<vector>());
 
     return true;
 }
diff --git a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
index 7e8ed9e187..3122030b02 100644
--- a/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
+++ b/src/mesh/snappyHexMesh/meshRefinement/meshRefinement.C
@@ -1973,7 +1973,7 @@ Foam::autoPtr<Foam::mapDistributePolyMesh> Foam::meshRefinement::balance
             labelList nProcCells(distributor.countCells(distribution));
             Pout<< "Wanted distribution:" << nProcCells << endl;
 
-            Pstream::listCombineAllGather(nProcCells, plusEqOp<label>());
+            Pstream::listCombineReduce(nProcCells, plusEqOp<label>());
 
             Pout<< "Wanted resulting decomposition:" << endl;
             forAll(nProcCells, proci)
diff --git a/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C b/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
index cefd97b46e..152ab78853 100644
--- a/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
+++ b/src/mesh/snappyHexMesh/meshRefinement/meshRefinementBaffles.C
@@ -823,7 +823,7 @@ Foam::autoPtr<Foam::mapPolyMesh> Foam::meshRefinement::createZoneBaffles
 
         if (nTotalBaffles > 0)
         {
-            Pstream::listCombineAllGather(nBaffles, plusEqOp<label>());
+            Pstream::listCombineReduce(nBaffles, plusEqOp<label>());
 
             Info<< nl
                 << setf(ios_base::left)
@@ -1953,7 +1953,7 @@ void Foam::meshRefinement::findCellZoneTopo
     // - region numbers are identical on all processors
     // - keepRegion is identical ,,
     // - cellZones are identical ,,
-    Pstream::listCombineAllGather(regionToCellZone, maxEqOp<label>());
+    Pstream::listCombineReduce(regionToCellZone, maxEqOp<label>());
 
 
     // Find the region containing the keepPoint
@@ -2003,7 +2003,7 @@ void Foam::meshRefinement::findCellZoneTopo
         // - cellZones are identical ,,
         // This done at top of loop to account for geometric matching
         // not being synchronised.
-        Pstream::listCombineAllGather(regionToCellZone, maxEqOp<label>());
+        Pstream::listCombineReduce(regionToCellZone, maxEqOp<label>());
 
 
         bool changed = false;
@@ -5862,7 +5862,7 @@ Foam::autoPtr<Foam::mapPolyMesh> Foam::meshRefinement::zonify
 
         // 2.Combine faceZoneNames allocated on different processors
 
-        Pstream::mapCombineAllGather(zonesToFaceZone, eqOp<word>());
+        Pstream::mapCombineReduce(zonesToFaceZone, eqOp<word>());
 
 
         // 3. Allocate faceZones from (now synchronised) faceZoneNames
@@ -6085,7 +6085,7 @@ Foam::autoPtr<Foam::mapPolyMesh> Foam::meshRefinement::zonify
                     nPosOrientation.find(faceToConnectedZone[faceI])() += n;
                 }
             }
-            Pstream::mapCombineAllGather(nPosOrientation, plusEqOp<label>());
+            Pstream::mapCombineReduce(nPosOrientation, plusEqOp<label>());
 
 
             Info<< "Split " << nFreeStanding << " free-standing zone faces"
diff --git a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
index 7fc5cccc86..ff5af5aedf 100644
--- a/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
+++ b/src/mesh/snappyHexMesh/snappyHexMeshDriver/snappyRefineDriver.C
@@ -3263,9 +3263,9 @@ void Foam::snappyRefineDriver::deleteSmallRegions
         nCellsPerRegion[regioni]++;
         nCellsPerZone[zonei]++;
     }
-    Pstream::listCombineAllGather(nCellsPerRegion, plusEqOp<label>());
-    Pstream::listCombineAllGather(regionToZone, maxEqOp<label>());
-    Pstream::listCombineAllGather(nCellsPerZone, plusEqOp<label>());
+    Pstream::listCombineReduce(nCellsPerRegion, plusEqOp<label>());
+    Pstream::listCombineReduce(regionToZone, maxEqOp<label>());
+    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
 
 
     // Mark small regions. Note that all processors have the same information
diff --git a/src/meshTools/coupling/externalFileCoupler.C b/src/meshTools/coupling/externalFileCoupler.C
index 95c6611f3f..19a544f3a2 100644
--- a/src/meshTools/coupling/externalFileCoupler.C
+++ b/src/meshTools/coupling/externalFileCoupler.C
@@ -282,9 +282,9 @@ Foam::externalFileCoupler::waitForMaster() const
         }
     }
 
-    label intAction(action);
-
-    Pstream::scatter(intAction); // Also acts as MPI barrier
+    // Send to sub-ranks. Also acts as an MPI barrier
+    int intAction(action);
+    Pstream::broadcast(intAction);
 
     return Time::stopAtControls(intAction);
 }
@@ -326,9 +326,9 @@ Foam::externalFileCoupler::waitForSlave() const
         Log << type() << ": found lock file " << lck << endl;
     }
 
-    label intAction(action);
-
-    Pstream::scatter(intAction); // Also acts as MPI barrier
+    // Send to sub-ranks. Also acts as an MPI barrier
+    int intAction(action);
+    Pstream::broadcast(intAction);
 
     return Time::stopAtControls(intAction);
 }
diff --git a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
index a1ea79bf9e..e4928adc3b 100644
--- a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
+++ b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
@@ -668,7 +668,7 @@ void Foam::mappedPatchBase::findSamples
 
 
     // Find nearest - globally consistent
-    Pstream::listCombineAllGather
+    Pstream::listCombineReduce
     (
         nearest,
         nearestWorldEqOp(),
diff --git a/src/meshTools/multiWorld/multiWorldConnectionsObject.C b/src/meshTools/multiWorld/multiWorldConnectionsObject.C
index f8d2c438ed..21efa3169e 100644
--- a/src/meshTools/multiWorld/multiWorldConnectionsObject.C
+++ b/src/meshTools/multiWorld/multiWorldConnectionsObject.C
@@ -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.
@@ -241,12 +241,7 @@ void Foam::multiWorldConnections::createComms()
 
     if (Pstream::parRun())
     {
-        Pstream::combineGather
-        (
-            allConnections,
-            worldConnectBitOrEq()
-        );
-        Pstream::scatter(allConnections);
+        Pstream::combineReduce(allConnections, worldConnectBitOrEq());
     }
 
     // Check for mismatched connections
diff --git a/src/meshTools/output/vtk/topoSet/foamVtkWriteTopoSet.H b/src/meshTools/output/vtk/topoSet/foamVtkWriteTopoSet.H
index 5f5a60e0d1..220ecb151b 100644
--- a/src/meshTools/output/vtk/topoSet/foamVtkWriteTopoSet.H
+++ b/src/meshTools/output/vtk/topoSet/foamVtkWriteTopoSet.H
@@ -70,7 +70,7 @@ bool writeTopoSet
     const topoSet& set,
     const vtk::outputOptions opts,
     const fileName& file,
-    bool parallel = Pstream::parRun()
+    bool parallel = UPstream::parRun()
 );
 
 
@@ -83,7 +83,7 @@ bool writeFaceSet
     const faceSet& set,
     const vtk::outputOptions opts,
     const fileName& file,
-    bool parallel = Pstream::parRun()
+    bool parallel = UPstream::parRun()
 );
 
 
@@ -96,7 +96,7 @@ bool writeCellSetFaces
     const cellSet& set,
     const vtk::outputOptions opts,
     const fileName& file,
-    bool parallel = Pstream::parRun()
+    bool parallel = UPstream::parRun()
 );
 
 
@@ -109,7 +109,7 @@ bool writePointSet
     const pointSet& set,
     const vtk::outputOptions opts,
     const fileName& file,
-    bool parallel = Pstream::parRun()
+    bool parallel = UPstream::parRun()
 );
 
 
diff --git a/src/meshTools/regionSplit2D/regionSplit2D.C b/src/meshTools/regionSplit2D/regionSplit2D.C
index d11518a062..dc22cde350 100644
--- a/src/meshTools/regionSplit2D/regionSplit2D.C
+++ b/src/meshTools/regionSplit2D/regionSplit2D.C
@@ -139,7 +139,7 @@ Foam::regionSplit2D::regionSplit2D
     // Ensure regionToCompactAddr consistent across all processors
     // - not concerned about the op (keys are unique)
     // - map size will be the number of regions in the set of faces
-    Pstream::mapCombineAllGather(regionToCompactAddr, minEqOp<label>());
+    Pstream::mapCombineReduce(regionToCompactAddr, minEqOp<label>());
 
     nRegions_ = regionToCompactAddr.size();
 
diff --git a/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C b/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
index af5db52e6f..1acd5127d0 100644
--- a/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
+++ b/src/meshTools/searchableSurfaces/triSurfaceMesh/triSurfaceMesh.C
@@ -462,7 +462,7 @@ Foam::triSurfaceMesh::triSurfaceMesh(const IOobject& io, const readAction r)
                     triSurface s2(actualFile);
                     triSurface::transfer(s2);
                 }
-                Pstream::scatter(triSurface::patches());
+                Pstream::broadcast(triSurface::patches());
                 if (debug)
                 {
                     Pout<< "triSurfaceMesh(const IOobject& io) :"
@@ -587,7 +587,7 @@ Foam::triSurfaceMesh::triSurfaceMesh
                     triSurface s2(actualFile, surfType, scaleFactor);
                     triSurface::transfer(s2);
                 }
-                Pstream::scatter(triSurface::patches());
+                Pstream::broadcast(triSurface::patches());
                 if (debug)
                 {
                     Pout<< "triSurfaceMesh(const IOobject& io) :"
diff --git a/src/meshTools/topoSet/cellSources/nearestToCell/nearestToCell.C b/src/meshTools/topoSet/cellSources/nearestToCell/nearestToCell.C
index d8560bc828..5ee762e039 100644
--- a/src/meshTools/topoSet/cellSources/nearestToCell/nearestToCell.C
+++ b/src/meshTools/topoSet/cellSources/nearestToCell/nearestToCell.C
@@ -85,7 +85,7 @@ void Foam::nearestToCell::combine(topoSet& set, const bool add) const
         );
     }
 
-    Pstream::listCombineAllGather(nearest, mappedPatchBase::nearestEqOp());
+    Pstream::listCombineReduce(nearest, mappedPatchBase::nearestEqOp());
 
     for (const auto& near : nearest)
     {
diff --git a/src/meshTools/topoSet/faceSources/regionToFace/regionToFace.C b/src/meshTools/topoSet/faceSources/regionToFace/regionToFace.C
index 8bbec46fc4..0df7ba37df 100644
--- a/src/meshTools/topoSet/faceSources/regionToFace/regionToFace.C
+++ b/src/meshTools/topoSet/faceSources/regionToFace/regionToFace.C
@@ -176,7 +176,7 @@ void Foam::regionToFace::combine(topoSet& set, const bool add) const
     }
 
     // Globally reduce
-    Pstream::combineAllGather(ni, mappedPatchBase::nearestEqOp());
+    Pstream::combineReduce(ni, mappedPatchBase::nearestEqOp());
 
     if (verbose_)
     {
diff --git a/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C b/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
index 45fd131a9d..c7cdff5f78 100644
--- a/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
+++ b/src/meshTools/topoSet/faceZoneSources/planeToFaceZone/planeToFaceZone.C
@@ -217,7 +217,7 @@ void Foam::planeToFaceZone::combine(faceZoneSet& fzSet, const bool add) const
                     regionRegions[regioni].unset(regioni);
                 }
             }
-            Pstream::listCombineAllGather(regionRegions, bitOrEqOp<bitSet>());
+            Pstream::listCombineReduce(regionRegions, bitOrEqOp<bitSet>());
 
             // Collapse the region connections into a map between each region
             // and the lowest numbered region that it connects to
@@ -258,7 +258,7 @@ void Foam::planeToFaceZone::combine(faceZoneSet& fzSet, const bool add) const
             {
                 ++ regionNFaces[regioni];
             }
-            Pstream::listCombineAllGather(regionNFaces, plusEqOp<label>());
+            Pstream::listCombineReduce(regionNFaces, plusEqOp<label>());
 
             Info<< "    Found " << nRegions << " contiguous regions with "
                 << regionNFaces << " faces" << endl;
diff --git a/src/meshTools/topoSet/pointSources/nearestToPoint/nearestToPoint.C b/src/meshTools/topoSet/pointSources/nearestToPoint/nearestToPoint.C
index d2deace74a..b5ec828161 100644
--- a/src/meshTools/topoSet/pointSources/nearestToPoint/nearestToPoint.C
+++ b/src/meshTools/topoSet/pointSources/nearestToPoint/nearestToPoint.C
@@ -104,7 +104,7 @@ void Foam::nearestToPoint::combine(topoSet& set, const bool add) const
     }
 
 
-    Pstream::listCombineAllGather(nearest, mappedPatchBase::nearestEqOp());
+    Pstream::listCombineReduce(nearest, mappedPatchBase::nearestEqOp());
 
     for (const auto& near : nearest)
     {
diff --git a/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C b/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
index 7c28e78019..89839e07b6 100644
--- a/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
+++ b/src/optimisation/adjointOptimisation/adjoint/parameterization/NURBS/NURBS3DVolume/NURBS3DVolume/NURBS3DVolume.C
@@ -1010,7 +1010,7 @@ Foam::vectorField Foam::NURBS3DVolume::computeControlPointSensitivities
     }
 
     // Sum contributions from all processors
-    Pstream::listCombineAllGather(controlPointDerivs, plusEqOp<vector>());
+    Pstream::listCombineReduce(controlPointDerivs, plusEqOp<vector>());
 
     return controlPointDerivs;
 }
@@ -1095,7 +1095,7 @@ Foam::vectorField Foam::NURBS3DVolume::computeControlPointSensitivities
         }
     }
     // Sum contributions from all processors
-    Pstream::listCombineAllGather(controlPointDerivs, plusEqOp<vector>());
+    Pstream::listCombineReduce(controlPointDerivs, plusEqOp<vector>());
 
     return controlPointDerivs;
 }
diff --git a/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C b/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
index 7883ca13c4..f57895b958 100644
--- a/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
+++ b/src/overset/cellCellStencil/cellVolumeWeight/cellVolumeWeightCellCellStencil.C
@@ -377,7 +377,7 @@ void Foam::cellCellStencils::cellVolumeWeight::findHoles
     {
         // Synchronise region status on processors
         // (could instead swap status through processor patches)
-        Pstream::listCombineAllGather(regionType, maxEqOp<label>());
+        Pstream::listCombineReduce(regionType, maxEqOp<label>());
 
         // Communicate region status through interpolative cells
         labelList cellRegionType(labelUIndList(regionType, cellRegion));
@@ -754,7 +754,7 @@ bool Foam::cellCellStencils::cellVolumeWeight::update()
     {
         nCellsPerZone[zoneID[cellI]]++;
     }
-    Pstream::listCombineAllGather(nCellsPerZone, plusEqOp<label>());
+    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
 
 
     Info<< typeName << " : detected " << nZones
diff --git a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
index a78a239fbd..ee52182aac 100644
--- a/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
+++ b/src/overset/cellCellStencil/inverseDistance/inverseDistanceCellCellStencil.C
@@ -1118,7 +1118,7 @@ void Foam::cellCellStencils::inverseDistance::findHoles
     {
         // Synchronise region status on processors
         // (could instead swap status through processor patches)
-        Pstream::listCombineAllGather(regionType, maxEqOp<label>());
+        Pstream::listCombineReduce(regionType, maxEqOp<label>());
 
         DebugInfo<< FUNCTION_NAME << " : Gathered region type" << endl;
 
@@ -1722,7 +1722,7 @@ bool Foam::cellCellStencils::inverseDistance::update()
     {
         nCellsPerZone[zoneID[cellI]]++;
     }
-    Pstream::listCombineAllGather(nCellsPerZone, plusEqOp<label>());
+    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
 
     const boundBox& allBb(mesh_.bounds());
 
diff --git a/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C b/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
index 66da7861bf..9b91a0f5bf 100644
--- a/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
+++ b/src/overset/cellCellStencil/trackingInverseDistance/trackingInverseDistanceCellCellStencil.C
@@ -517,7 +517,7 @@ Foam::cellCellStencils::trackingInverseDistance::trackingInverseDistance
     {
         nCellsPerZone[zoneID[celli]]++;
     }
-    Pstream::listCombineAllGather(nCellsPerZone, plusEqOp<label>());
+    Pstream::listCombineReduce(nCellsPerZone, plusEqOp<label>());
 
     meshParts_.setSize(nZones);
     forAll(meshParts_, zonei)
diff --git a/src/overset/regionsToCell/findRefCells.C b/src/overset/regionsToCell/findRefCells.C
index b949b80ec1..0704f355ba 100644
--- a/src/overset/regionsToCell/findRefCells.C
+++ b/src/overset/regionsToCell/findRefCells.C
@@ -68,7 +68,7 @@ void Foam::setRefCells
             }
         }
 
-        Pstream::listCombineAllGather(regionNeedReference, orEqOp<bool>());
+        Pstream::listCombineReduce(regionNeedReference, orEqOp<bool>());
     }
 
 
@@ -188,7 +188,7 @@ void Foam::setRefCells
             }
         }
 
-        Pstream::listCombineAllGather(hasRef, plusEqOp<label>());
+        Pstream::listCombineReduce(hasRef, plusEqOp<label>());
 
         forAll(hasRef, regionI)
         {
diff --git a/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C b/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
index 588a233c99..28d7e1dc78 100644
--- a/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
+++ b/src/parallel/decompose/decompositionMethods/decompositionMethod/decompositionMethod.C
@@ -480,7 +480,7 @@ void Foam::decompositionMethod::calcCellCells
     // Create global cell numbers
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-    const globalIndex globalAgglom(nLocalCoarse, Pstream::worldComm, parallel);
+    const globalIndex globalAgglom(nLocalCoarse, UPstream::worldComm, parallel);
 
 
     // Get agglomerate owner on other side of coupled faces
@@ -673,7 +673,7 @@ void Foam::decompositionMethod::calcCellCells
     // Create global cell numbers
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-    const globalIndex globalAgglom(nLocalCoarse, Pstream::worldComm, parallel);
+    const globalIndex globalAgglom(nLocalCoarse, UPstream::worldComm, parallel);
 
 
     // Get agglomerate owner on other side of coupled faces
diff --git a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
index e541e49a7c..f291df37ff 100644
--- a/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
+++ b/src/parallel/decompose/decompositionMethods/multiLevelDecomp/multiLevelDecomp.C
@@ -419,11 +419,7 @@ void Foam::multiLevelDecomp::decompose
 
             label nPoints = returnReduce(domainPoints.size(), sumOp<label>());
 
-            Pstream::listCombineAllGather
-            (
-                nOutsideConnections,
-                plusEqOp<label>()
-            );
+            Pstream::listCombineReduce(nOutsideConnections, plusEqOp<label>());
             label nPatches = 0;
             label nFaces = 0;
             for (const label nConnect : nOutsideConnections)
@@ -530,7 +526,7 @@ void Foam::multiLevelDecomp::decompose
                 }
 
                 reduce(nPoints, sumOp<label>());
-                Pstream::listCombineAllGather
+                Pstream::listCombineReduce
                 (
                     nOutsideConnections,
                     plusEqOp<label>()
diff --git a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
index 7516828651..e8b3345785 100644
--- a/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
+++ b/src/parallel/reconstruct/faReconstruct/faMeshReconstructor.C
@@ -101,7 +101,7 @@ void Foam::faMeshReconstructor::calcAddressing
               ? 0
               : singlePatchFaceLabels_.first()
             );
-            Pstream::scatter(patchFirstMeshfacei);
+            Pstream::broadcast(patchFirstMeshfacei);
 
             for (label& facei : faFaceProcAddr_)
             {
@@ -169,7 +169,7 @@ void Foam::faMeshReconstructor::calcAddressing
     }
 
     // Broadcast the same information everywhere
-    Pstream::scatter(singlePatchFaceLabels_);
+    Pstream::broadcast(singlePatchFaceLabels_);
 
 
     // ------------------
@@ -283,7 +283,7 @@ void Foam::faMeshReconstructor::calcAddressing
                 mpm[mp[i]] = i;
             }
         }
-        Pstream::scatter(mpm);
+        Pstream::broadcast(mpm);
 
         // Rewrite pointToGlobal according to the correct point order
         for (label& pointi : pointToGlobal)
@@ -299,8 +299,8 @@ void Foam::faMeshReconstructor::calcAddressing
     }
 
     // Broadcast the same information everywhere
-    Pstream::scatter(singlePatchFaces_);
-    Pstream::scatter(singlePatchPoints_);
+    Pstream::broadcast(singlePatchFaces_);
+    Pstream::broadcast(singlePatchPoints_);
 
     // Now have enough global information to determine global edge mappings
 
@@ -383,13 +383,8 @@ void Foam::faMeshReconstructor::calcAddressing
         // OR patchEdgeLabels =
         // UIndirectList<label>(faEdgeProcAddr_, fap.edgeLabels());
 
-
-        // Collect from all processors
-        Pstream::combineAllGather
-        (
-            patchEdgeLabels,
-            ListOps::appendEqOp<label>()
-        );
+        // Combine from all processors
+        Pstream::combineReduce(patchEdgeLabels, ListOps::appendEqOp<label>());
 
         // Sorted order will be the original non-decomposed order
         Foam::sort(patchEdgeLabels);
diff --git a/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C b/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
index fb2f837509..ff95490d56 100644
--- a/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
+++ b/src/regionModels/regionModel/singleLayerRegion/singleLayerRegion.C
@@ -142,7 +142,7 @@ void Foam::regionModels::singleLayerRegion::initialise()
         }
     }
 
-    Pstream::listCombineAllGather(passivePatchIDs_, maxEqOp<label>());
+    Pstream::listCombineReduce(passivePatchIDs_, maxEqOp<label>());
 
     magSf.field() = 0.5*(magSf + passiveMagSf);
     magSf.correctBoundaryConditions();
diff --git a/src/rigidBodyDynamics/rigidBodyMotion/rigidBodyMotion.C b/src/rigidBodyDynamics/rigidBodyMotion/rigidBodyMotion.C
index 1430ad67fd..cc03840da3 100644
--- a/src/rigidBodyDynamics/rigidBodyMotion/rigidBodyMotion.C
+++ b/src/rigidBodyDynamics/rigidBodyMotion/rigidBodyMotion.C
@@ -190,7 +190,7 @@ void Foam::RBD::rigidBodyMotion::solve
         solver_->solve(tau, fx);
     }
 
-    Pstream::scatter(motionState_);
+    Pstream::broadcast(motionState_);
 
     // Update the body-state to correspond to the current joint-state
     forwardDynamicsCorrection(motionState_);
diff --git a/src/sampling/probes/patchProbes.C b/src/sampling/probes/patchProbes.C
index 7ea65d3c0f..08515512e4 100644
--- a/src/sampling/probes/patchProbes.C
+++ b/src/sampling/probes/patchProbes.C
@@ -166,7 +166,7 @@ void Foam::patchProbes::findElements(const fvMesh& mesh)
 
 
     // Find nearest - globally consistent
-    Pstream::listCombineAllGather(nearest, mappedPatchBase::nearestEqOp());
+    Pstream::listCombineReduce(nearest, mappedPatchBase::nearestEqOp());
 
     oldPoints_.resize(this->size());
 
diff --git a/src/sampling/probes/patchProbesTemplates.C b/src/sampling/probes/patchProbesTemplates.C
index 1666236eb7..c8c82e5ce0 100644
--- a/src/sampling/probes/patchProbesTemplates.C
+++ b/src/sampling/probes/patchProbesTemplates.C
@@ -111,7 +111,7 @@ Foam::patchProbes::sample(const VolumeField<Type>& vField) const
         }
     }
 
-    Pstream::listCombineAllGather(values, isNotEqOp<Type>());
+    Pstream::listCombineReduce(values, isNotEqOp<Type>());
 
     return tvalues;
 }
@@ -141,7 +141,7 @@ Foam::patchProbes::sample(const SurfaceField<Type>& sField) const
         }
     }
 
-    Pstream::listCombineAllGather(values, isNotEqOp<Type>());
+    Pstream::listCombineReduce(values, isNotEqOp<Type>());
 
     return tvalues;
 }
diff --git a/src/sampling/probes/probesTemplates.C b/src/sampling/probes/probesTemplates.C
index ea5bef4b5e..72c44fc914 100644
--- a/src/sampling/probes/probesTemplates.C
+++ b/src/sampling/probes/probesTemplates.C
@@ -225,7 +225,7 @@ Foam::probes::sample(const VolumeField<Type>& vField) const
         }
     }
 
-    Pstream::listCombineAllGather(values, isNotEqOp<Type>());
+    Pstream::listCombineReduce(values, isNotEqOp<Type>());
 
     return tvalues;
 }
@@ -248,7 +248,7 @@ Foam::probes::sample(const SurfaceField<Type>& sField) const
         }
     }
 
-    Pstream::listCombineAllGather(values, isNotEqOp<Type>());
+    Pstream::listCombineReduce(values, isNotEqOp<Type>());
 
     return tvalues;
 }
diff --git a/src/sampling/sampledSet/cloud/cloudSet.C b/src/sampling/sampledSet/cloud/cloudSet.C
index 48f61a1eb8..42045d473c 100644
--- a/src/sampling/sampledSet/cloud/cloudSet.C
+++ b/src/sampling/sampledSet/cloud/cloudSet.C
@@ -84,8 +84,8 @@ void Foam::cloudSet::calcSamples
             minFoundProc[i] = foundProc[i];
         }
     }
-    Pstream::listCombineAllGather(minFoundProc, minEqOp<label>());
-    Pstream::listCombineAllGather(maxFoundProc, maxEqOp<label>());
+    Pstream::listCombineReduce(minFoundProc, minEqOp<label>());
+    Pstream::listCombineReduce(maxFoundProc, maxEqOp<label>());
 
 
     DynamicField<point> missingPoints(sampleCoords_.size());
diff --git a/src/sampling/sampledSet/patchCloud/patchCloudSet.C b/src/sampling/sampledSet/patchCloud/patchCloudSet.C
index f97a1848ff..3b3a9567fc 100644
--- a/src/sampling/sampledSet/patchCloud/patchCloudSet.C
+++ b/src/sampling/sampledSet/patchCloud/patchCloudSet.C
@@ -155,7 +155,7 @@ void Foam::patchCloudSet::calcSamples
 
 
     // Find nearest - globally consistent
-    Pstream::listCombineAllGather(nearest, mappedPatchBase::nearestEqOp());
+    Pstream::listCombineReduce(nearest, mappedPatchBase::nearestEqOp());
 
 
     if (debug && Pstream::master())
diff --git a/src/sampling/sampledSet/patchSeed/patchSeedSet.C b/src/sampling/sampledSet/patchSeed/patchSeedSet.C
index 390300e4cd..b2efaa46ce 100644
--- a/src/sampling/sampledSet/patchSeed/patchSeedSet.C
+++ b/src/sampling/sampledSet/patchSeed/patchSeedSet.C
@@ -178,11 +178,7 @@ void Foam::patchSeedSet::calcSamples
             // 2. Reduce on master. Select nearest processor.
 
             // Find nearest - globally consistent
-            Pstream::listCombineAllGather
-            (
-                nearest,
-                mappedPatchBase::nearestEqOp()
-            );
+            Pstream::listCombineReduce(nearest, mappedPatchBase::nearestEqOp());
 
             // 3. Pick up my local faces that have won
 
diff --git a/src/sampling/sampledSet/sampledSets/sampledSets.C b/src/sampling/sampledSet/sampledSets/sampledSets.C
index 63248a47ae..cafe0ef330 100644
--- a/src/sampling/sampledSet/sampledSets/sampledSets.C
+++ b/src/sampling/sampledSet/sampledSets/sampledSets.C
@@ -196,7 +196,7 @@ Foam::IOobjectList Foam::sampledSets::preCheckFields(unsigned request)
 
     // Parallel consistency (no-op in serial)
     // Probably not needed...
-    /// Pstream::mapCombineAllGather(selected, HashSetOps::plusEqOp<word>());
+    /// Pstream::mapCombineReduce(selected, HashSetOps::plusEqOp<word>());
 
 
     DynamicList<label> missed(fieldSelection_.size());
diff --git a/src/sampling/sampledSet/shortestPath/shortestPathSet.C b/src/sampling/sampledSet/shortestPath/shortestPathSet.C
index 8e09eabfdf..12fb3059ef 100644
--- a/src/sampling/sampledSet/shortestPath/shortestPathSet.C
+++ b/src/sampling/sampledSet/shortestPath/shortestPathSet.C
@@ -264,7 +264,7 @@ void Foam::shortestPathSet::sync
             celli,
             Tuple2<point, bool>(origin, findMinDistance)
         );
-        Pstream::combineAllGather
+        Pstream::combineReduce
         (
             searchData,
             [](ProcData& x, const ProcData& y)
diff --git a/src/sampling/sampledSurface/sampledMeshedSurface/sampledMeshedSurface.C b/src/sampling/sampledSurface/sampledMeshedSurface/sampledMeshedSurface.C
index 24b0180a92..2cb85c8425 100644
--- a/src/sampling/sampledSurface/sampledMeshedSurface/sampledMeshedSurface.C
+++ b/src/sampling/sampledSurface/sampledMeshedSurface/sampledMeshedSurface.C
@@ -227,7 +227,7 @@ bool Foam::sampledMeshedSurface::update(const meshSearch& meshSearcher)
     // See which processor has the nearest. Mark and subset
     // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-    Pstream::listCombineAllGather(nearest, minFirstEqOp<scalar>{});
+    Pstream::listCombineReduce(nearest, minFirstEqOp<scalar>{});
 
     labelList cellOrFaceLabels(fc.size(), -1);
 
diff --git a/src/sampling/sampledSurface/sampledSurfaces/sampledSurfaces.C b/src/sampling/sampledSurface/sampledSurfaces/sampledSurfaces.C
index aaa102c9bb..d187fb3b76 100644
--- a/src/sampling/sampledSurface/sampledSurfaces/sampledSurfaces.C
+++ b/src/sampling/sampledSurface/sampledSurfaces/sampledSurfaces.C
@@ -119,7 +119,7 @@ Foam::IOobjectList Foam::sampledSurfaces::preCheckFields()
     }
 
     // Parallel consistency (no-op in serial)
-    Pstream::mapCombineAllGather(selected, HashSetOps::plusEqOp<word>());
+    Pstream::mapCombineReduce(selected, HashSetOps::plusEqOp<word>());
 
 
     DynamicList<label> missed(fieldSelection_.size());
diff --git a/src/sampling/surface/isoSurface/isoSurfacePoint.C b/src/sampling/surface/isoSurface/isoSurfacePoint.C
index b4be87d417..348a2bce34 100644
--- a/src/sampling/surface/isoSurface/isoSurfacePoint.C
+++ b/src/sampling/surface/isoSurface/isoSurfacePoint.C
@@ -262,7 +262,7 @@ void Foam::isoSurfacePoint::syncUnseparatedPoints
         }
 
         // Globally consistent
-        Pstream::listCombineAllGather(sharedPts, minEqOp<point>());
+        Pstream::listCombineReduce(sharedPts, minEqOp<point>());
 
         // Now we will all have the same information. Merge it back with
         // my local information.
diff --git a/src/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.C b/src/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.C
index 6e3d91d315..8240a1305c 100644
--- a/src/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.C
+++ b/src/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion/sixDoFRigidBodyMotion.C
@@ -323,7 +323,7 @@ void Foam::sixDoFRigidBodyMotion::update
         }
     }
 
-    Pstream::scatter(motionState_);
+    Pstream::broadcast(motionState_);
 }
 
 
diff --git a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/TDACChemistryModel.C b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/TDACChemistryModel.C
index 8bfbca15fb..6d355fbe23 100644
--- a/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/TDACChemistryModel.C
+++ b/src/thermophysicalModels/chemistryModel/chemistryModel/TDACChemistryModel/TDACChemistryModel.C
@@ -867,7 +867,7 @@ Foam::scalar Foam::TDACChemistryModel<ReactionThermo, ThermoType>::solve
     if (reduced && Pstream::parRun())
     {
         List<bool> active(composition.active());
-        Pstream::listCombineAllGather(active, orEqOp<bool>());
+        Pstream::listCombineReduce(active, orEqOp<bool>());
 
         forAll(active, i)
         {
diff --git a/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C b/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
index db623f1d84..2013255abc 100644
--- a/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
+++ b/src/thermophysicalModels/radiation/radiationModels/solarLoad/faceReflecting/faceReflecting.C
@@ -329,8 +329,8 @@ void Foam::faceReflecting::calculate()
     // Distribute ray indexes to all proc's
     // Make sure all the processors have the same information
 
-    Pstream::listCombineAllGather(refDisDirsIndex, maxEqOp<label>());
-    Pstream::mapCombineAllGather(refFacesDirIndex, minEqOp<label>());
+    Pstream::listCombineReduce(refDisDirsIndex, maxEqOp<label>());
+    Pstream::mapCombineReduce(refFacesDirIndex, minEqOp<label>());
 
     scalar maxBounding = 5.0*mag(mesh_.bounds().max() - mesh_.bounds().min());
 
diff --git a/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C b/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
index 29e9994da5..4ead682bbb 100644
--- a/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
+++ b/src/thermophysicalModels/radiation/radiationModels/viewFactor/viewFactor.C
@@ -977,13 +977,9 @@ void Foam::radiation::viewFactor::calculate()
                 qrExt[compactGlobalIds[i]] = compactCoarseHo[i];
             }
 
-            Pstream::listCombineGather(T4, maxEqOp<scalar>());
-            Pstream::listCombineGather(E, maxEqOp<scalar>());
-            Pstream::listCombineGather(qrExt, maxEqOp<scalar>());
-
-            Pstream::listCombineScatter(T4);
-            Pstream::listCombineScatter(E);
-            Pstream::listCombineScatter(qrExt);
+            Pstream::listCombineReduce(T4, maxEqOp<scalar>());
+            Pstream::listCombineReduce(E, maxEqOp<scalar>());
+            Pstream::listCombineReduce(qrExt, maxEqOp<scalar>());
 
             if (Pstream::master())
             {