ENH: parallel makeFaMesh with addressing and field decomposition (#2084)

applications/utilities/finiteArea/makeFaMesh/Make/options

 EXE_INC = \
     -I$(LIB_SRC)/finiteArea/lnInclude \
-    -I$(LIB_SRC)/finiteVolume/lnInclude \
     -I$(LIB_SRC)/fileFormats/lnInclude \
     -I$(LIB_SRC)/meshTools/lnInclude \
-    -I$(LIB_SRC)/cfdTools/general/lnInclude
+    -I$(LIB_SRC)/parallel/decompose/faDecompose/lnInclude \
+    -I$(LIB_SRC)/parallel/reconstruct/faReconstruct/lnInclude
 
 EXE_LIBS = \
     -lfiniteArea \
-    -lfiniteVolume \
     -lfileFormats \
-    -lmeshTools
+    -lmeshTools \
+    -lfaDecompose \
+    -lfaReconstruct

applications/utilities/finiteArea/makeFaMesh/decomposeFaFields.H

@@ -11,13 +11,84 @@ License
     This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
 
 Description
-    placeholder for decomposing fields
+    Decompose area fields, when mesh was generated in parallel
 
 \*---------------------------------------------------------------------------*/
 
 if (Pstream::parRun())
 {
-}
+    faMeshReconstructor reconstructor(areaMesh);
+    reconstructor.writeAddressing();
+
+    // Handle area fields
+    // ------------------
+
+    PtrList<areaScalarField> areaScalarFields;
+    PtrList<areaVectorField> areaVectorFields;
+    PtrList<areaSphericalTensorField> areaSphTensorFields;
+    PtrList<areaSymmTensorField> areaSymmTensorFields;
+    PtrList<areaTensorField> areaTensorFields;
+
+    const faMesh& fullMesh = reconstructor.mesh();
+
+    {
+        // Use uncollated (or master uncollated) file handler here.
+        // - each processor is reading in the identical serial fields.
+        // - nothing should be parallel-coordinated.
+
+        // Similarly, if we write the serial finite-area mesh, this is only
+        // done from one processor!
+
+        reconstructor.writeMesh();
+
+        const bool oldDistributed = fileHandler().distributed();
+        auto oldHandler = fileHandler(fileOperation::NewUncollated());
+        fileHandler().distributed(true);
 
+        IOobjectList objects(fullMesh.time(), runTime.timeName());
+
+        faFieldDecomposer::readFields(fullMesh, objects, areaScalarFields);
+        faFieldDecomposer::readFields(fullMesh, objects, areaVectorFields);
+        faFieldDecomposer::readFields(fullMesh, objects, areaSphTensorFields);
+        faFieldDecomposer::readFields(fullMesh, objects, areaSymmTensorFields);
+        faFieldDecomposer::readFields(fullMesh, objects, areaTensorFields);
+
+        // Restore old settings
+        if (oldHandler)
+        {
+            fileHandler(std::move(oldHandler));
+        }
+        fileHandler().distributed(oldDistributed);
+    }
+
+    const label nAreaFields =
+    (
+        areaScalarFields.size()
+      + areaVectorFields.size()
+      + areaSphTensorFields.size()
+      + areaSymmTensorFields.size()
+      + areaTensorFields.size()
+    );
+
+    if (nAreaFields)
+    {
+        Info<< "Decomposing " << nAreaFields << " area fields" << nl << endl;
+
+        faFieldDecomposer fieldDecomposer
+        (
+            fullMesh,
+            areaMesh,
+            reconstructor.edgeProcAddressing(),
+            reconstructor.faceProcAddressing(),
+            reconstructor.boundaryProcAddressing()
+        );
+
+        fieldDecomposer.decomposeFields(areaScalarFields);
+        fieldDecomposer.decomposeFields(areaVectorFields);
+        fieldDecomposer.decomposeFields(areaSphTensorFields);
+        fieldDecomposer.decomposeFields(areaSymmTensorFields);
+        fieldDecomposer.decomposeFields(areaTensorFields);
+    }
+}
 
 // ************************************************************************* //

applications/utilities/finiteArea/makeFaMesh/faMeshWriteEdgesOBJ.H

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2021 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM, distributed under GPL-3.0-or-later.
+
+Description
+    OBJ output of faMesh edges
+
+\*---------------------------------------------------------------------------*/
+
+{
+    Info<< "Writing edges in obj format" << endl;
+
+    word outputName("faMesh-edges.obj");
+
+    if (Pstream::parRun())
+    {
+        outputName = word
+        (
+            "faMesh-edges-" + Foam::name(Pstream::myProcNo()) + ".obj"
+        );
+    }
+
+    OBJstream os(runTime.globalPath()/outputName);
+
+    os.writeQuoted
+    (
+        ("# " + outputName + "\n"),
+        false
+    );
+
+    os.write(areaMesh.patch().edges(), areaMesh.patch().localPoints());
+}
+
+
+// ************************************************************************* //

applications/utilities/finiteArea/makeFaMesh/makeFaMesh.C

@@ -29,6 +29,8 @@ Application
 
 Description
     A mesh generator for finiteArea mesh.
+    When called in parallel, it will also try to act like decomposePar,
+    create procAddressing and decompose serial finite-area fields.
 
 Author
     Zeljko Tukovic, FAMENA
@@ -36,15 +38,17 @@ Author
 
 \*---------------------------------------------------------------------------*/
 
-#include "objectRegistry.H"
 #include "Time.H"
 #include "argList.H"
 #include "OSspecific.H"
 #include "faMesh.H"
-#include "fvMesh.H"
 #include "IOdictionary.H"
-#include "globalIndex.H"
-#include "globalMeshData.H"
+#include "IOobjectList.H"
+
+#include "areaFields.H"
+#include "faFieldDecomposer.H"
+#include "faMeshReconstructor.H"
+#include "OBJstream.H"
 
 using namespace Foam;
 
@@ -65,10 +69,17 @@ int main(int argc, char *argv[])
     );
     argList::addOption("dict", "file", "Alternative faMeshDefinition");
 
+    argList::addBoolOption
+    (
+        "write-edges-obj",
+        "Write mesh edges as obj files and exit",
+        false  // could make an advanced option
+    );
+
     #include "addRegionOption.H"
     #include "setRootCase.H"
     #include "createTime.H"
-    #include "createNamedMesh.H"
+    #include "createNamedPolyMesh.H"
 
     // Reading faMeshDefinition dictionary
     #include "findMeshDefinitionDict.H"
@@ -80,12 +91,29 @@ int main(int argc, char *argv[])
         meshDefDict.add("emptyPatch", patchName, true);
     }
 
-    // Creation
+    // Create
     faMesh areaMesh(mesh, meshDefDict);
 
-    // Writing faMesh
-    Info << "Write finite area mesh ... ";
+    bool quickExit = false;
+
+    if (args.found("write-edges-obj"))
+    {
+        quickExit = true;
+        #include "faMeshWriteEdgesOBJ.H"
+    }
+
+    if (quickExit)
+    {
+        Info<< "\nEnd\n" << endl;
+        return 0;
+    }
+
+    // Set the precision of the points data to 10
+    IOstream::defaultPrecision(10);
+
+    Info<< nl << "Write finite area mesh." << nl;
     areaMesh.write();
+    Info<< endl;
 
     #include "decomposeFaFields.H"