data/src/mesh/snappyHexMesh/meshRefinement/meshRefinementMerge.C

/*---------------------------------------------------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Copyright (C) 2011-2026 OpenFOAM Foundation
     \\/     M anipulation  |
-------------------------------------------------------------------------------
License
    This file is part of OpenFOAM.

    OpenFOAM is free software: you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    for more details.

    You should have received a copy of the GNU General Public License
    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.

\*---------------------------------------------------------------------------*/

#include "meshRefinement.H"
#include "combineFaces.H"
#include "polyTopoChange.H"
#include "removePoints.H"
#include "faceSet.H"
#include "Time.H"
#include "meshCheck.H"
#include "syncTools.H"

// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //

//// Merge faces that are in-line.
//Foam::label Foam::meshRefinement::mergePatchFaces
//(
//    const scalar minCos,
//    const scalar concaveCos,
//    const labelList& patchIDs
//)
//{
//    // Patch face merging engine
//    combineFaces faceCombiner(mesh_);
//
//    const polyBoundaryMesh& patches = mesh_.poly().boundary();
//
//    // Pick up all candidate cells on boundary
//    labelHashSet boundaryCells(mesh_.nFaces()-mesh_.nInternalFaces());
//
//    forAll(patchIDs, i)
//    {
//        label patchi = patchIDs[i];
//
//        const polyPatch& patch = patches[patchi];
//
//        if (!patch.coupled())
//        {
//            forAll(patch, i)
//            {
//                boundaryCells.insert(mesh_.faceOwner()[patch.start()+i]);
//            }
//        }
//    }
//
//    // Get all sets of faces that can be merged
//    labelListList mergeSets
//    (
//        faceCombiner.getMergeSets
//        (
//            minCos,
//            concaveCos,
//            boundaryCells
//        )
//    );
//
//    label nFaceSets = returnReduce(mergeSets.size(), sumOp());
//
//    Info<< "mergePatchFaces : Merging " << nFaceSets
//        << " sets of faces." << endl;
//
//    if (nFaceSets > 0)
//    {
//        // Topology changes container
//        polyTopoChange meshMod(mesh_);
//
//        // Merge all faces of a set into the first face of the set. Remove
//        // unused points.
//        faceCombiner.setRefinement(mergeSets, meshMod);
//
//        // Change the mesh (without keeping old points)
//        autoPtr<polyTopoChangeMap> map =
//            meshMod.changeMesh(mesh_, true);
//
//        // Update fields
//        mesh_.topoChange(map);
//
//        // Reset the instance for if in overwrite mode
//        mesh_.setInstance(name());
//
//        faceCombiner.topoChange(map);
//
//        // Get the kept faces that need to be recalculated.
//        // Merging two boundary faces might shift the cell centre
//        // (unless the faces are absolutely planar)
//        labelHashSet retestFaces(6*mergeSets.size());
//
//        forAll(mergeSets, seti)
//        {
//            label oldMasterI = mergeSets[seti][0];
//
//            label facei = map().reverseFaceMap()[oldMasterI];
//
//            // facei is always uncoupled boundary face
//            const cell& cFaces = mesh_.cells()[mesh_.faceOwner()[facei]];
//
//            forAll(cFaces, i)
//            {
//                retestFaces.insert(cFaces[i]);
//            }
//        }
//        topoChange(map, retestFaces.toc());
//    }
//
//
//    return nFaceSets;
//}
//
//
//// Remove points not used by any face or points used by only two faces where
//// the edges are in line
//Foam::autoPtr<Foam::polyTopoChangeMap> Foam::meshRefinement::mergeEdges
//(
//    const scalar minCos
//)
//{
//    // Point removal analysis engine
//    removePoints pointRemover(mesh_);
//
//    // Count usage of points
//    boolList pointCanBeDeleted;
//    label nRemove = pointRemover.countPointUsage(minCos, pointCanBeDeleted);
//
//    Info<< "Removing " << nRemove
//        << " straight edge points." << endl;
//
//    autoPtr<polyTopoChangeMap> map;
//
//    if (nRemove > 0)
//    {
//        // Save my local faces that will change. These changed faces might
//        // cause a shift in the cell centre which needs to be retested.
//        // Have to do this before changing mesh since point will be removed.
//        labelHashSet retestOldFaces(nRemove / Pstream::nProcs());
//
//        {
//            const faceList& faces = mesh_.faces();
//
//            forAll(faces, facei)
//            {
//                const face& f = faces[facei];
//
//                forAll(f, fp)
//                {
//                    if (pointCanBeDeleted[f[fp]])
//                    {
//                        retestOldFaces.insert(facei);
//                        break;
//                    }
//                }
//            }
//        }
//
//        // Topology changes container
//        polyTopoChange meshMod(mesh_);
//
//        pointRemover.setRefinement(pointCanBeDeleted, meshMod);
//
//        // Change the mesh (without keeping old points)
//        map = meshMod.changeMesh(mesh_, true);
//
//        // Update fields
//        mesh_.topoChange(map);
//
//        // Reset the instance for if in overwrite mode
//        mesh_.setInstance(name());
//
//        pointRemover.topoChange(map);
//
//        // Get the kept faces that need to be recalculated.
//        labelHashSet retestFaces(6*retestOldFaces.size());
//
//        const cellList& cells = mesh_.cells();
//
//        forAllConstIter(labelHashSet, retestOldFaces, iter)
//        {
//            label facei = map().reverseFaceMap()[iter.key()];
//
//            const cell& ownFaces = cells[mesh_.faceOwner()[facei]];
//
//            forAll(ownFaces, i)
//            {
//                retestFaces.insert(ownFaces[i]);
//            }
//
//            if (mesh_.isInternalFace(facei))
//            {
//                const cell& neiFaces = cells[mesh_.faceNeighbour()[facei]];
//
//                forAll(neiFaces, i)
//                {
//                    retestFaces.insert(neiFaces[i]);
//                }
//            }
//        }
//        topoChange(map, retestFaces.toc());
//    }
//
//    return map;
//}


Foam::label Foam::meshRefinement::mergePatchFacesUndo
(
    const scalar minCos,
    const scalar concaveCos,
    const labelHashSet& patchIDs,
    const dictionary& motionDict,
    const labelList& preserveFaces
)
{
    // Patch face merging engine
    combineFaces faceCombiner(mesh_, true);

    // Get all sets of faces that can be merged. Since only faces on the same
    // patch get merged there is no risk of e.g. patchID faces getting merged
    // with original patches (or even processor patches). There is a risk
    // though of original patch faces getting merged if they make a small
    // angle. Would be pretty weird starting mesh though.
    labelListList allFaceSets
    (
        faceCombiner.getMergeSets(minCos, concaveCos, patchIDs)
    );

    // Filter out any set that contains any preserveFace
    label compactI = 0;
    forAll(allFaceSets, i)
    {
        const labelList& set = allFaceSets[i];

        bool keep = true;
        forAll(set, j)
        {
            if (preserveFaces[set[j]] != -1)
            {
                keep = false;
                break;
            }
        }

        if (keep)
        {
            if (compactI != i)
            {
                allFaceSets[compactI] = set;
            }

            compactI++;
        }
    }
    allFaceSets.setSize(compactI);

    label nFaceSets = returnReduce(allFaceSets.size(), sumOp());

    Info<< "Merging " << nFaceSets << " sets of faces." << nl << endl;

    if (nFaceSets > 0)
    {
        if (debug&meshRefinement::MESH)
        {
            faceSet allSets(mesh_, "allFaceSets", allFaceSets.size());
            forAll(allFaceSets, seti)
            {
                forAll(allFaceSets[seti], i)
                {
                    allSets.insert(allFaceSets[seti][i]);
                }
            }
            Pout<< "Writing all faces to be merged to set "
                << allSets.objectPath() << endl;
            allSets.instance() = name();
            allSets.write();

            const_cast<Time&>(mesh_.time())++;
        }


        // Topology changes container
        polyTopoChange meshMod(mesh_);

        // Merge all faces of a set into the first face of the set.
        faceCombiner.setRefinement(allFaceSets, meshMod);

        // Change the mesh
        autoPtr<polyTopoChangeMap> map = meshMod.changeMesh(mesh_, true);

        // Update fields
        mesh_.topoChange(map);

        // Reset the instance for if in overwrite mode
        mesh_.setInstance(name());

        faceCombiner.topoChange(map);

        // Get the kept faces that need to be recalculated.
        // Merging two boundary faces might shift the cell centre
        // (unless the faces are absolutely planar)
        labelHashSet retestFaces(2*allFaceSets.size());

        forAll(allFaceSets, seti)
        {
            const label oldMasterI = allFaceSets[seti][0];
            retestFaces.insert(map().reverseFaceMap()[oldMasterI]);
        }
        topoChange(map, growFaceCellFace(retestFaces));

        if (debug&meshRefinement::MESH)
        {
            // Check sync
            Pout<< "Checking sync after initial merging " << nFaceSets
                << " faces." << endl;
            checkData();

            Pout<< "Writing initial merged-faces mesh to time "
                << name() << nl << endl;
            write();
        }

        for (label iteration = 0; iteration < 100; iteration++)
        {
            Info<< nl
                << "Undo iteration " << iteration << nl
                << "----------------" << endl;


            // Check mesh for errors
            // ~~~~~~~~~~~~~~~~~~~~~

            faceSet errorFaces
            (
                mesh_,
                "errorFaces",
                mesh_.nFaces()-mesh_.nInternalFaces()
            );
            bool hasErrors = meshCheck::checkMesh
            (
                false,  // report
                mesh_,
                motionDict,
                errorFaces
            );

            // if (checkEdgeConnectivity)
            //{
            //    Info<< "Checking edge-face connectivity (duplicate faces"
            //        << " or non-consecutive shared vertices)" << endl;
            //
            //    label nOldSize = errorFaces.size();
            //
            //    hasErrors =
            //        mesh_.checkFaceFaces
            //        (
            //            false,
            //            &errorFaces
            //        )
            //     || hasErrors;
            //
            //    Info<< "Detected additional "
            //        <<  returnReduce
            //            (
            //                errorFaces.size() - nOldSize,
            //                sumOp()
            //            )
            //        << " faces with illegal face-face connectivity"
            //        << endl;
            //}

            if (!hasErrors)
            {
                break;
            }


            if (debug&meshRefinement::MESH)
            {
                errorFaces.instance() = name();
                Pout<< "Writing all faces in error to faceSet "
                    << errorFaces.objectPath() << nl << endl;
                errorFaces.write();
            }


            // Check any master cells for using any of the error faces
            // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

            DynamicList<label> mastersToRestore(allFaceSets.size());

            forAll(allFaceSets, seti)
            {
                const label masterFacei = faceCombiner.masterFace()[seti];

                if (masterFacei != -1)
                {
                    const label masterCellII = mesh_.faceOwner()[masterFacei];

                    const cell& cFaces = mesh_.cells()[masterCellII];

                    forAll(cFaces, i)
                    {
                        if (errorFaces.found(cFaces[i]))
                        {
                            mastersToRestore.append(masterFacei);
                            break;
                        }
                    }
                }
            }
            mastersToRestore.shrink();

            const label nRestore = returnReduce
            (
                mastersToRestore.size(),
                sumOp()
            );

            Info<< "Masters that need to be restored:"
                << nRestore << endl;

            if (debug&meshRefinement::MESH)
            {
                faceSet restoreSet(mesh_, "mastersToRestore", mastersToRestore);
                restoreSet.instance() = name();
                Pout<< "Writing all " << mastersToRestore.size()
                    << " masterfaces to be restored to set "
                    << restoreSet.objectPath() << endl;
                restoreSet.write();
            }


            if (nRestore == 0)
            {
                break;
            }


            // Undo
            // ~~~~

            if (debug)
            {
                const_cast<Time&>(mesh_.time())++;
            }

            // Topology changes container
            polyTopoChange meshMod(mesh_);

            // Merge all faces of a set into the first face of the set.
            Map<label> restoredFaces(0);
            faceCombiner.setUnrefinement
            (
                mastersToRestore,
                meshMod,
                restoredFaces
            );

            // Change the mesh (without keeping old points)
            autoPtr<polyTopoChangeMap> map = meshMod.changeMesh(mesh_, true);

            // Update fields
            mesh_.topoChange(map);

            // Reset the instance for if in overwrite mode
            mesh_.setInstance(name());

            faceCombiner.topoChange(map);

            // Renumber restore maps
            inplaceMapKey(map().reverseFaceMap(), restoredFaces);

            // Get the kept faces that need to be recalculated.
            // Merging two boundary faces might shift the cell centre
            // (unless the faces are absolutely planar)
            labelHashSet retestFaces(2*restoredFaces.size());
            forAllConstIter(Map<label>, restoredFaces, iter)
            {
                retestFaces.insert(iter.key());
            }

            topoChange(map, growFaceCellFace(retestFaces));

            if (debug&meshRefinement::MESH)
            {
                // Check sync
                Pout<< "Checking sync after restoring " << retestFaces.size()
                    << " faces." << endl;
                checkData();

                Pout<< "Writing merged-faces mesh to time "
                    << name() << nl << endl;
                write();
            }

            Info<< endl;
        }
    }
    else
    {
        Info<< "No faces merged ..." << endl;
    }

    return nFaceSets;
}


// Remove points. pointCanBeDeleted is parallel synchronised.
Foam::autoPtr<Foam::polyTopoChangeMap> Foam::meshRefinement::doRemovePoints
(
    removePoints& pointRemover,
    const boolList& pointCanBeDeleted
)
{
    // Topology changes container
    polyTopoChange meshMod(mesh_);

    pointRemover.setRefinement(pointCanBeDeleted, meshMod);

    // Change the mesh
    autoPtr<polyTopoChangeMap> map = meshMod.changeMesh(mesh_, true);

    // Update fields
    mesh_.topoChange(map);

    // Reset the instance for if in overwrite mode
    mesh_.setInstance(name());

    pointRemover.topoChange(map);


    // Retest all affected faces and all the cells using them
    labelHashSet retestFaces(pointRemover.savedFaceLabels().size());
    forAll(pointRemover.savedFaceLabels(), i)
    {
        const label facei = pointRemover.savedFaceLabels()[i];
        if (facei >= 0)
        {
            retestFaces.insert(facei);
        }
    }
    topoChange(map, growFaceCellFace(retestFaces));

    if (debug)
    {
        // Check sync
        Pout<< "Checking sync after removing points." << endl;
        checkData();
    }

    return map;
}


Foam::autoPtr<Foam::polyTopoChangeMap> Foam::meshRefinement::doRestorePoints
(
    removePoints& pointRemover,
    const labelList& facesToRestore
)
{
    // Topology changes container
    polyTopoChange meshMod(mesh_);

    // Determine sets of points and faces to restore
    labelList localFaces, localPoints;
    pointRemover.getUnrefimentSet
    (
        facesToRestore,
        localFaces,
        localPoints
    );

    // Undo the changes on the faces that are in error.
    pointRemover.setUnrefinement
    (
        localFaces,
        localPoints,
        meshMod
    );

    // Change the mesh
    autoPtr<polyTopoChangeMap> map = meshMod.changeMesh(mesh_, true);

    // Update fields
    mesh_.topoChange(map);

    // Reset the instance for if in overwrite mode
    mesh_.setInstance(name());

    pointRemover.topoChange(map);

    labelHashSet retestFaces(2*facesToRestore.size());
    forAll(facesToRestore, i)
    {
        const label facei = map().reverseFaceMap()[facesToRestore[i]];
        if (facei >= 0)
        {
            retestFaces.insert(facei);
        }
    }
    topoChange(map, growFaceCellFace(retestFaces));

    if (debug)
    {
        // Check sync
        Pout<< "Checking sync after restoring points on "
            << facesToRestore.size() << " faces." << endl;
        checkData();
    }

    return map;
}


// Collect all faces that are both in candidateFaces and in the set.
// If coupled face also collects the coupled face.
Foam::labelList Foam::meshRefinement::collectFaces
(
    const labelList& candidateFaces,
    const labelHashSet& set
) const
{
    // Has face been selected?
    boolList selected(mesh_.nFaces(), false);

    forAll(candidateFaces, i)
    {
        const label facei = candidateFaces[i];

        if (set.found(facei))
        {
            selected[facei] = true;
        }
    }
    syncTools::syncFaceList
    (
        mesh_,
        selected,
        orEqOp()      // combine operator
    );

    labelList selectedFaces(findIndices(selected, true));

    return selectedFaces;
}


// Pick up faces of cells of faces in set.
Foam::labelList Foam::meshRefinement::growFaceCellFace
(
    const labelHashSet& set
) const
{
    boolList selected(mesh_.nFaces(), false);

    forAllConstIter(faceSet, set, iter)
    {
        const label facei = iter.key();
        const label own = mesh_.faceOwner()[facei];

        const cell& ownFaces = mesh_.cells()[own];
        forAll(ownFaces, ownFacei)
        {
            selected[ownFaces[ownFacei]] = true;
        }

        if (mesh_.isInternalFace(facei))
        {
            const label nbr = mesh_.faceNeighbour()[facei];

            const cell& nbrFaces = mesh_.cells()[nbr];
            forAll(nbrFaces, nbrFacei)
            {
                selected[nbrFaces[nbrFacei]] = true;
            }
        }
    }
    syncTools::syncFaceList
    (
        mesh_,
        selected,
        orEqOp()      // combine operator
    );
    return findIndices(selected, true);
}


// Remove points not used by any face or points used by only two faces where
// the edges are in line
Foam::label Foam::meshRefinement::mergeEdgesUndo
(
    const scalar minCos,
    const dictionary& motionDict
)
{
    Info<< nl
        << "Merging all points on surface that" << nl
        << "- are used by only two boundary faces and" << nl
        << "- make an angle with a cosine of more than " << minCos
        << "." << nl << endl;

    // Point removal analysis engine with undo
    removePoints pointRemover(mesh_, true);

    // Count usage of points
    boolList pointCanBeDeleted;
    label nRemove = pointRemover.countPointUsage(minCos, pointCanBeDeleted);

    if (nRemove > 0)
    {
        Info<< "Removing " << nRemove
            << " straight edge points ..." << nl << endl;

        // Remove points
        // ~~~~~~~~~~~~~

        doRemovePoints(pointRemover, pointCanBeDeleted);


        for (label iteration = 0; iteration < 100; iteration++)
        {
            Info<< nl
                << "Undo iteration " << iteration << nl
                << "----------------" << endl;


            // Check mesh for errors
            // ~~~~~~~~~~~~~~~~~~~~~

            faceSet errorFaces
            (
                mesh_,
                "errorFaces",
                mesh_.nFaces()-mesh_.nInternalFaces()
            );
            bool hasErrors = meshCheck::checkMesh
            (
                false,  // report
                mesh_,
                motionDict,
                errorFaces
            );
            // if (checkEdgeConnectivity)
            //{
            //    Info<< "Checking edge-face connectivity (duplicate faces"
            //        << " or non-consecutive shared vertices)" << endl;
            //
            //    label nOldSize = errorFaces.size();
            //
            //    hasErrors =
            //        mesh_.checkFaceFaces
            //        (
            //            false,
            //            &errorFaces
            //        )
            //     || hasErrors;
            //
            //    Info<< "Detected additional "
            //        << returnReduce(errorFaces.size()-nOldSize,sumOp())
            //        << " faces with illegal face-face connectivity"
            //        << endl;
            //}

            if (!hasErrors)
            {
                break;
            }

            if (debug&meshRefinement::MESH)
            {
                errorFaces.instance() = name();
                Pout<< "**Writing all faces in error to faceSet "
                    << errorFaces.objectPath() << nl << endl;
                errorFaces.write();
            }

            labelList masterErrorFaces
            (
                collectFaces
                (
                    pointRemover.savedFaceLabels(),
                    errorFaces
                )
            );

            const label n = returnReduce
            (
                masterErrorFaces.size(),
                sumOp()
            );

            Info<< "Detected " << n
                << " error faces on boundaries that have been merged."
                << " These will be restored to their original faces." << nl
                << endl;

            if (n == 0)
            {
                if (hasErrors)
                {
                    Info<< "Detected "
                        << returnReduce(errorFaces.size(), sumOp())
                        << " error faces in mesh."
                        << " Restoring neighbours of faces in error." << nl
                        << endl;

                    labelList expandedErrorFaces
                    (
                        growFaceCellFace
                        (
                            errorFaces
                        )
                    );

                    doRestorePoints(pointRemover, expandedErrorFaces);
                }

                break;
            }

            doRestorePoints(pointRemover, masterErrorFaces);
        }

        if (debug&meshRefinement::MESH)
        {
            const_cast<Time&>(mesh_.time())++;
            Pout<< "Writing merged-edges mesh to time "
                << name() << nl << endl;
            write();
        }
    }
    else
    {
        Info<< "No straight edges simplified and no points removed ..." << endl;
    }

    return nRemove;
}


// ************************************************************************* //