From af8161925be8fb8e72e1bba9d221fac459b60ef3 Mon Sep 17 00:00:00 2001
From: Mark Olesen <Mark.Olesen@esi-group.com>
Date: Fri, 25 Feb 2022 17:42:57 +0100
Subject: [PATCH] ENH: use mpi gather for list values in a few places

- avoid gatherList/scatterList when value are only need on master
---
 .../laserDTRM/Make/options                    |   2 +
 .../laserDTRM/laserDTRM.C                     |  55 +++-----
 .../redistributePar/redistributePar.C         |  12 +-
 .../surfaceRedistributePar.C                  |  57 ++++----
 .../db/IOstreams/Fstreams/masterOFstream.C    |   7 +-
 .../AMIInterpolation/AMIInterpolation.C       |  52 +++----
 .../mappedPolyPatch/mappedPatchBase.C         |  18 +--
 .../distributedTriSurfaceMesh.C               | 129 ++++++++++--------
 .../meshToMesh/meshToMeshParallelOps.C        |  47 +++----
 9 files changed, 180 insertions(+), 199 deletions(-)

diff --git a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/Make/options b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/Make/options
index 43f3302bba..f5f200dd5f 100644
--- a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/Make/options
+++ b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/Make/options
@@ -3,12 +3,14 @@ phaseSystem = $(LIB_SRC)/phaseSystemModels/multiphaseInter
 EXE_INC = \
     -I${phaseSystem}/phasesSystem/lnInclude \
     -I$(LIB_SRC)/finiteVolume/lnInclude \
+    -I$(LIB_SRC)/fileFormats/lnInclude \
     -I$(LIB_SRC)/meshTools/lnInclude \
     -I$(LIB_SRC)/lagrangian/basic/lnInclude \
     -I$(LIB_SRC)/thermophysicalModels/radiation/lnInclude
 
 LIB_LIBS = \
     -lfiniteVolume \
+    -lfileFormats \
     -lmeshTools \
     -llagrangian \
     -lradiationModels \
diff --git a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/laserDTRM.C b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/laserDTRM.C
index 4e75bf8c40..1ebeb9601d 100644
--- a/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/laserDTRM.C
+++ b/applications/solvers/multiphase/icoReactingMultiphaseInterFoam/laserDTRM/laserDTRM.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.
@@ -31,11 +31,12 @@ License
 #include "absorptionEmissionModel.H"
 #include "scatterModel.H"
 #include "constants.H"
-#include "addToRunTimeSelectionTable.H"
 #include "unitConversion.H"
 #include "interpolationCell.H"
 #include "interpolationCellPoint.H"
 #include "Random.H"
+#include "OBJstream.H"
+#include "addToRunTimeSelectionTable.H"
 
 using namespace Foam::constant;
 
@@ -679,44 +680,28 @@ void Foam::radiation::laserDTRM::calculate()
         Info<< "Final number of particles..."
             << returnReduce(DTRMCloud_.size(), sumOp<label>()) << endl;
 
-        OFstream osRef(type() + ":particlePath.obj");
-        label vertI = 0;
-
-        List<pointField> positions(Pstream::nProcs());
-        List<pointField> p0(Pstream::nProcs());
-
-        DynamicList<point>  positionsMyProc;
-        DynamicList<point>  p0MyProc;
-
-        for (const DTRMParticle& p : DTRMCloud_)
+        pointField lines(2*DTRMCloud_.size());
         {
-            positionsMyProc.append(p.position());
-            p0MyProc.append(p.p0());
-        }
-
-        positions[Pstream::myProcNo()].transfer(positionsMyProc);
-        p0[Pstream::myProcNo()].transfer(p0MyProc);
-
-        Pstream::gatherList(positions);
-        Pstream::scatterList(positions);
-        Pstream::gatherList(p0);
-        Pstream::scatterList(p0);
-
-        for (const int proci : Pstream::allProcs())
-        {
-            const pointField& pos = positions[proci];
-            const pointField& pfinal = p0[proci];
-            forAll(pos, i)
+            label i = 0;
+            for (const DTRMParticle& p : DTRMCloud_)
             {
-                meshTools::writeOBJ(osRef, pos[i]);
-                vertI++;
-                meshTools::writeOBJ(osRef, pfinal[i]);
-                vertI++;
-                osRef << "l " << vertI-1 << ' ' << vertI << nl;
+                lines[i] = p.position();
+                lines[i+1] = p.p0();
+                i += 2;
             }
         }
 
-        osRef.flush();
+        globalIndex::gatherInplaceOp(lines);
+
+        if (Pstream::master())
+        {
+            OBJstream os(type() + ":particlePath.obj");
+
+            for (label pointi = 0; pointi < lines.size(); pointi += 2)
+            {
+                os.write(linePointRef(lines[pointi], lines[pointi+1]));
+            }
+        }
 
         scalar totalQ = gSum(Q_.primitiveFieldRef()*mesh_.V());
         Info << "Total energy absorbed [W]: " << totalQ << endl;
diff --git a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
index 03c3097dea..cca7e2d2c0 100644
--- a/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
+++ b/applications/utilities/parallelProcessing/redistributePar/redistributePar.C
@@ -261,15 +261,17 @@ boolList haveFacesFile(const fileName& meshPath)
 {
     const fileName facesPath(meshPath/"faces");
     Info<< "Checking for mesh in " << facesPath << nl << endl;
-    boolList haveMesh(Pstream::nProcs(), false);
-    haveMesh[Pstream::myProcNo()] = fileHandler().isFile
+    boolList haveMesh
     (
-        fileHandler().filePath(facesPath)
+        UPstream::listGatherValues<bool>
+        (
+            fileHandler().isFile(fileHandler().filePath(facesPath))
+        )
     );
-    Pstream::gatherList(haveMesh);
-    Pstream::scatterList(haveMesh);
     Info<< "Per processor mesh availability:" << nl
         << "    " << flatOutput(haveMesh) << nl << endl;
+
+    Pstream::broadcast(haveMesh);
     return haveMesh;
 }
 
diff --git a/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C b/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
index f85a35534e..8728809ffd 100644
--- a/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
+++ b/applications/utilities/surface/surfaceRedistributePar/surfaceRedistributePar.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -63,41 +63,38 @@ void writeProcStats
 {
     // Determine surface bounding boxes, faces, points
     List<treeBoundBox> surfBb(Pstream::nProcs());
+    surfBb[Pstream::myProcNo()] = treeBoundBox(s.points());
+    Pstream::gatherList(surfBb);
+
+    labelList nPoints(UPstream::listGatherValues<label>(s.points().size()));
+    labelList nFaces(UPstream::listGatherValues<label>(s.size()));
+
+    if (Pstream::master())
     {
-        surfBb[Pstream::myProcNo()] = treeBoundBox(s.points());
-        Pstream::gatherList(surfBb);
-        Pstream::scatterList(surfBb);
-    }
-
-    labelList nPoints(Pstream::nProcs());
-    nPoints[Pstream::myProcNo()] = s.points().size();
-    Pstream::gatherList(nPoints);
-    Pstream::scatterList(nPoints);
-
-    labelList nFaces(Pstream::nProcs());
-    nFaces[Pstream::myProcNo()] = s.size();
-    Pstream::gatherList(nFaces);
-    Pstream::scatterList(nFaces);
-
-    forAll(surfBb, proci)
-    {
-        Info<< "processor" << proci << nl;
-
-        const List<treeBoundBox>& bbs = meshBb[proci];
-        if (bbs.size())
+        forAll(surfBb, proci)
         {
-            Info<< "\tMesh bounds          : " << bbs[0] << nl;
-            for (label i = 1; i < bbs.size(); i++)
+            Info<< "processor" << proci << nl;
+
+            const List<treeBoundBox>& bbs = meshBb[proci];
+            forAll(bbs, i)
             {
-                Info<< "\t                       " << bbs[i]<< nl;
+                if (!i)
+                {
+                    Info<< "\tMesh bounds          : ";
+                }
+                else
+                {
+                    Info<< "\t                       ";
+                }
+                Info<< bbs[i] << nl;
             }
+            Info<< "\tSurface bounding box : " << surfBb[proci] << nl
+                << "\tTriangles            : " << nFaces[proci] << nl
+                << "\tVertices             : " << nPoints[proci]
+                << endl;
         }
-        Info<< "\tSurface bounding box : " << surfBb[proci] << nl
-            << "\tTriangles            : " << nFaces[proci] << nl
-            << "\tVertices             : " << nPoints[proci]
-            << endl;
+        Info<< endl;
     }
-    Info<< endl;
 }
 
 
diff --git a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
index f6608a5b7c..c8de005a4d 100644
--- a/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
+++ b/src/OpenFOAM/db/IOstreams/Fstreams/masterOFstream.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2017 OpenFOAM Foundation
-    Copyright (C) 2020-2021 OpenCFD Ltd.
+    Copyright (C) 2020-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -115,10 +115,7 @@ void Foam::masterOFstream::commit()
             return;
         }
 
-        boolList valid(Pstream::nProcs());
-        valid[Pstream::myProcNo()] = valid_;
-        Pstream::gatherList(valid);
-
+        boolList valid(UPstream::listGatherValues<bool>(valid_));
 
         // Different files
         PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
diff --git a/src/meshTools/AMIInterpolation/AMIInterpolation/AMIInterpolation.C b/src/meshTools/AMIInterpolation/AMIInterpolation/AMIInterpolation.C
index 36887ad927..382ddfa653 100644
--- a/src/meshTools/AMIInterpolation/AMIInterpolation/AMIInterpolation.C
+++ b/src/meshTools/AMIInterpolation/AMIInterpolation/AMIInterpolation.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.
@@ -79,47 +79,37 @@ Foam::label Foam::AMIInterpolation::calcDistribution
     const primitivePatch& tgtPatch
 ) const
 {
+    // Either not parallel or no faces on any processor
     label proci = 0;
 
     if (Pstream::parRun())
     {
-        labelList facesPresentOnProc(Pstream::nProcs(), Zero);
-        if ((srcPatch.size() > 0) || (tgtPatch.size() > 0))
+        const bitSet hasFaces
+        (
+            UPstream::listGatherValues<bool>
+            (
+                srcPatch.size() > 0 || tgtPatch.size() > 0
+            )
+        );
+
+        const auto nHaveFaces = hasFaces.count();
+
+        if (nHaveFaces == 1)
         {
-            facesPresentOnProc[Pstream::myProcNo()] = 1;
+            proci = hasFaces.find_first();
+            DebugInFunction
+                << "AMI local to processor" << proci << endl;
         }
-        else
-        {
-            facesPresentOnProc[Pstream::myProcNo()] = 0;
-        }
-
-        Pstream::gatherList(facesPresentOnProc);
-        Pstream::scatterList(facesPresentOnProc);
-
-        label nHaveFaces = sum(facesPresentOnProc);
-
-        if (nHaveFaces > 1)
+        else if (nHaveFaces > 1)
         {
             proci = -1;
-            if (debug)
-            {
-                InfoInFunction
-                    << "AMI split across multiple processors" << endl;
-            }
-        }
-        else if (nHaveFaces == 1)
-        {
-            proci = facesPresentOnProc.find(1);
-            if (debug)
-            {
-                InfoInFunction
-                    << "AMI local to processor" << proci << endl;
-            }
+            DebugInFunction
+                << "AMI split across multiple processors" << endl;
         }
+
+        Pstream::broadcast(proci);
     }
 
-
-    // Either not parallel or no faces on any processor
     return proci;
 }
 
diff --git a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
index 20da1aaaf7..1857ffa774 100644
--- a/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
+++ b/src/meshTools/mappedPatches/mappedPolyPatch/mappedPatchBase.C
@@ -241,15 +241,17 @@ void Foam::mappedPatchBase::collectSamples
     }
 
     {
-        labelList procToWorldIndex(nProcs);
-        procToWorldIndex[myRank] = mySampleWorld;
-        Pstream::gatherList(procToWorldIndex, Pstream::msgType(), myComm);
-        Pstream::scatterList(procToWorldIndex, Pstream::msgType(), myComm);
+        labelList procToWorldIndex
+        (
+            UPstream::listGatherValues<label>(mySampleWorld, myComm)
+        );
+        Pstream::broadcast(procToWorldIndex, myComm);
 
-        labelList nPerProc(nProcs);
-        nPerProc[myRank] = patch_.size();
-        Pstream::gatherList(nPerProc, Pstream::msgType(), myComm);
-        Pstream::scatterList(nPerProc, Pstream::msgType(), myComm);
+        labelList nPerProc
+        (
+            UPstream::listGatherValues<label>(patch_.size(), myComm)
+        );
+        Pstream::broadcast(nPerProc, myComm);
 
         patchFaceWorlds.setSize(patchFaces.size());
         patchFaceProcs.setSize(patchFaces.size());
diff --git a/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C b/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
index 0f2ab38b60..81d02cc131 100644
--- a/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
+++ b/src/parallel/distributed/distributedTriSurfaceMesh/distributedTriSurfaceMesh.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2020 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -2475,18 +2475,21 @@ Foam::distributedTriSurfaceMesh::distributedTriSurfaceMesh
         InfoInFunction << "Constructed from triSurface:" << endl;
         writeStats(Info);
 
-        labelList nTris(Pstream::nProcs());
-        nTris[Pstream::myProcNo()] = triSurface::size();
-        Pstream::gatherList(nTris);
-        Pstream::scatterList(nTris);
+        labelList nTris
+        (
+            UPstream::listGatherValues<label>(triSurface::size())
+        );
 
-        Info<< endl<< "\tproc\ttris\tbb" << endl;
-        forAll(nTris, proci)
+        if (Pstream::master())
         {
-            Info<< '\t' << proci << '\t' << nTris[proci]
-                 << '\t' << procBb_[proci] << endl;
+            Info<< endl<< "\tproc\ttris\tbb" << endl;
+            forAll(nTris, proci)
+            {
+                Info<< '\t' << proci << '\t' << nTris[proci]
+                    << '\t' << procBb_[proci] << endl;
+            }
+            Info<< endl;
         }
-        Info<< endl;
     }
 }
 
@@ -2573,18 +2576,21 @@ Foam::distributedTriSurfaceMesh::distributedTriSurfaceMesh(const IOobject& io)
                 << "Read distributedTriSurface " << io.name()
                 << " from actual path " << actualFile << ':' << endl;
 
-            labelList nTris(Pstream::nProcs());
-            nTris[Pstream::myProcNo()] = triSurface::size();
-            Pstream::gatherList(nTris);
-            Pstream::scatterList(nTris);
+            labelList nTris
+            (
+                UPstream::listGatherValues<label>(triSurface::size())
+            );
 
-            Info<< endl<< "\tproc\ttris\tbb" << endl;
-            forAll(nTris, proci)
+            if (Pstream::master())
             {
-                Info<< '\t' << proci << '\t' << nTris[proci]
-                     << '\t' << procBb_[proci] << endl;
+                Info<< endl<< "\tproc\ttris\tbb" << endl;
+                forAll(nTris, proci)
+                {
+                    Info<< '\t' << proci << '\t' << nTris[proci]
+                        << '\t' << procBb_[proci] << endl;
+                }
+                Info<< endl;
             }
-            Info<< endl;
         }
     }
     if (debug)
@@ -2714,18 +2720,21 @@ Foam::distributedTriSurfaceMesh::distributedTriSurfaceMesh
                 << " from actual path " << actualFile
                 << " and dictionary:" << endl;
 
-            labelList nTris(Pstream::nProcs());
-            nTris[Pstream::myProcNo()] = triSurface::size();
-            Pstream::gatherList(nTris);
-            Pstream::scatterList(nTris);
+            labelList nTris
+            (
+                UPstream::listGatherValues<label>(triSurface::size())
+            );
 
-            Info<< endl<< "\tproc\ttris\tbb" << endl;
-            forAll(nTris, proci)
+            if (Pstream::master())
             {
-                Info<< '\t' << proci << '\t' << nTris[proci]
-                     << '\t' << procBb_[proci] << endl;
+                Info<< endl<< "\tproc\ttris\tbb" << endl;
+                forAll(nTris, proci)
+                {
+                    Info<< '\t' << proci << '\t' << nTris[proci]
+                        << '\t' << procBb_[proci] << endl;
+                }
+                Info<< endl;
             }
-            Info<< endl;
         }
     }
     if (debug)
@@ -4534,19 +4543,22 @@ void Foam::distributedTriSurfaceMesh::distribute
     // Debug information
     if (debug)
     {
-        labelList nTris(Pstream::nProcs());
-        nTris[Pstream::myProcNo()] = triSurface::size();
-        Pstream::gatherList(nTris);
-        Pstream::scatterList(nTris);
+        labelList nTris
+        (
+            UPstream::listGatherValues<label>(triSurface::size())
+        );
 
-        InfoInFunction
-            << "before distribution:" << endl << "\tproc\ttris" << endl;
-
-        forAll(nTris, proci)
+        if (Pstream::master())
         {
-            Info<< '\t' << proci << '\t' << nTris[proci] << endl;
+            InfoInFunction
+                << "before distribution:" << endl << "\tproc\ttris" << endl;
+
+            forAll(nTris, proci)
+            {
+                Info<< '\t' << proci << '\t' << nTris[proci] << endl;
+            }
+            Info<< endl;
         }
-        Info<< endl;
     }
 
 
@@ -4757,32 +4769,33 @@ void Foam::distributedTriSurfaceMesh::distribute
 
     if (debug)
     {
-        labelList nTris(Pstream::nProcs());
-        nTris[Pstream::myProcNo()] = triSurface::size();
-        Pstream::gatherList(nTris);
-        Pstream::scatterList(nTris);
+        labelList nTris
+        (
+            UPstream::listGatherValues<label>(triSurface::size())
+        );
 
-        InfoInFunction
-            << "after distribution:" << endl << "\tproc\ttris" << endl;
-
-        forAll(nTris, proci)
+        if (Pstream::master())
         {
-            Info<< '\t' << proci << '\t' << nTris[proci] << endl;
+            InfoInFunction
+                << "after distribution:" << endl << "\tproc\ttris" << endl;
+
+            forAll(nTris, proci)
+            {
+                Info<< '\t' << proci << '\t' << nTris[proci] << endl;
+            }
+            Info<< endl;
         }
-        Info<< endl;
 
         if (debug & 2)
         {
             OBJstream str(searchableSurface::time().path()/"after.obj");
             Info<< "Writing local bounding box to " << str.name() << endl;
             const List<treeBoundBox>& myBbs = procBb_[Pstream::myProcNo()];
-            forAll(myBbs, i)
+            for (const treeBoundBox& bb : myBbs)
             {
-                pointField pts(myBbs[i].points());
-                const edgeList& es = treeBoundBox::edges;
-                forAll(es, ei)
+                pointField pts(bb.points());
+                for (const edge& e : treeBoundBox::edges)
                 {
-                    const edge& e = es[ei];
                     str.write(linePointRef(pts[e[0]], pts[e[1]]));
                 }
             }
@@ -4791,15 +4804,13 @@ void Foam::distributedTriSurfaceMesh::distribute
         {
             OBJstream str(searchableSurface::time().path()/"after_all.obj");
             Info<< "Writing all bounding boxes to " << str.name() << endl;
-            for (auto myBbs : procBb_)
+            for (const auto& myBbs : procBb_)
             {
-                forAll(myBbs, i)
+                for (const treeBoundBox& bb : myBbs)
                 {
-                    pointField pts(myBbs[i].points());
-                    const edgeList& es = treeBoundBox::edges;
-                    forAll(es, ei)
+                    pointField pts(bb.points());
+                    for (const edge& e : treeBoundBox::edges)
                     {
-                        const edge& e = es[ei];
                         str.write(linePointRef(pts[e[0]], pts[e[1]]));
                     }
                 }
diff --git a/src/sampling/meshToMesh/meshToMeshParallelOps.C b/src/sampling/meshToMesh/meshToMeshParallelOps.C
index b58d795239..71e89311a5 100644
--- a/src/sampling/meshToMesh/meshToMeshParallelOps.C
+++ b/src/sampling/meshToMesh/meshToMeshParallelOps.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2017 OpenFOAM Foundation
-    Copyright (C) 2015-2021 OpenCFD Ltd.
+    Copyright (C) 2015-2022 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,35 +48,30 @@ Foam::label Foam::meshToMesh::calcDistribution
 
     if (Pstream::parRun())
     {
-        List<label> cellsPresentOnProc(Pstream::nProcs(), Zero);
-        if ((src.nCells() > 0) || (tgt.nCells() > 0))
+        const bitSet hasMesh
+        (
+            UPstream::listGatherValues<bool>
+            (
+                src.nCells() > 0 || tgt.nCells() > 0
+            )
+        );
+
+        const auto nHaveMesh = hasMesh.count();
+
+        if (nHaveMesh == 1)
         {
-            cellsPresentOnProc[Pstream::myProcNo()] = 1;
-        }
-        else
-        {
-            cellsPresentOnProc[Pstream::myProcNo()] = 0;
-        }
-
-        Pstream::gatherList(cellsPresentOnProc);
-        Pstream::scatterList(cellsPresentOnProc);
-
-        label nHaveCells = sum(cellsPresentOnProc);
-
-        if (nHaveCells > 1)
-        {
-            proci = -1;
-
-            DebugInFunction
-                << "Meshes split across multiple processors" << endl;
-        }
-        else if (nHaveCells == 1)
-        {
-            proci = cellsPresentOnProc.find(1);
-
+            proci = hasMesh.find_first();
             DebugInFunction
                 << "Meshes local to processor" << proci << endl;
         }
+        else if (nHaveMesh > 1)
+        {
+            proci = -1;
+            DebugInFunction
+                << "Meshes split across multiple processors" << endl;
+        }
+
+        Pstream::broadcast(proci);
     }
 
     return proci;