Date: 2026-03-31T05:46:07+00:00

Actual source code: plexfvm.c

      1: #include <petsc/private/dmpleximpl.h>
      2: #include <petscsf.h>

      4: #include <petsc/private/petscfeimpl.h>
      5: #include <petsc/private/petscfvimpl.h>

      7: static PetscErrorCode DMPlexApplyLimiter_Internal(DM dm, DM dmCell, PetscLimiter lim, PetscInt dim, PetscInt dof, PetscInt cell, PetscInt field, PetscInt face, PetscInt fStart, PetscInt fEnd, PetscReal *cellPhi, const PetscScalar *x, const PetscScalar *cellgeom, const PetscFVCellGeom *cg, const PetscScalar *cx, const PetscScalar *cgrad)
      8: {
      9:   const PetscInt *children;
     10:   PetscInt        numChildren;

     12:   PetscFunctionBegin;
     13:   PetscCall(DMPlexGetTreeChildren(dm, face, &numChildren, &children));
     14:   if (numChildren) {
     15:     PetscInt c;

     17:     for (c = 0; c < numChildren; c++) {
     18:       PetscInt childFace = children[c];

     20:       if (childFace >= fStart && childFace < fEnd) PetscCall(DMPlexApplyLimiter_Internal(dm, dmCell, lim, dim, dof, cell, field, childFace, fStart, fEnd, cellPhi, x, cellgeom, cg, cx, cgrad));
     21:     }
     22:   } else {
     23:     PetscScalar     *ncx;
     24:     PetscFVCellGeom *ncg;
     25:     const PetscInt  *fcells;
     26:     PetscInt         Ns, ncell, d;
     27:     PetscReal        v[3];

     29:     PetscCall(DMPlexGetSupport(dm, face, &fcells));
     30:     PetscCall(DMPlexGetSupportSize(dm, face, &Ns));
     31:     if (Ns < 2) {
     32:       for (d = 0; d < dof; ++d) cellPhi[d] = 1.0;
     33:       PetscFunctionReturn(PETSC_SUCCESS);
     34:     }
     35:     ncell = cell == fcells[0] ? fcells[1] : fcells[0];
     36:     if (field >= 0) PetscCall(DMPlexPointLocalFieldRead(dm, ncell, field, x, &ncx));
     37:     else PetscCall(DMPlexPointLocalRead(dm, ncell, x, &ncx));
     38:     PetscCall(DMPlexPointLocalRead(dmCell, ncell, cellgeom, &ncg));
     39:     DMPlex_WaxpyD_Internal(dim, -1, cg->centroid, ncg->centroid, v);
     40:     for (d = 0; d < dof; ++d) {
     41:       /* We use the symmetric slope limited form of Berger, Aftosmis, and Murman 2005 */
     42:       PetscReal denom = DMPlex_DotD_Internal(dim, &cgrad[d * dim], v);
     43:       PetscReal fact  = denom == 0 ? 1.0e+30 : 1 / denom;
     44:       PetscReal phi, flim = 0.5 * PetscRealPart(ncx[d] - cx[d]) * fact;

     46:       PetscCall(PetscLimiterLimit(lim, flim, &phi));
     47:       cellPhi[d] = PetscMin(cellPhi[d], phi);
     48:     }
     49:   }
     50:   PetscFunctionReturn(PETSC_SUCCESS);
     51: }

     53: PetscErrorCode DMPlexReconstructGradients_Internal(DM dm, PetscFV fvm, PetscInt fStart, PetscInt fEnd, Vec faceGeometry, Vec cellGeometry, Vec locX, Vec grad)
     54: {
     55:   DM                 dmFace, dmCell, dmGrad;
     56:   DMLabel            ghostLabel;
     57:   PetscDS            prob;
     58:   PetscLimiter       lim;
     59:   PetscLimiterType   limType;
     60:   const PetscScalar *facegeom, *cellgeom, *x;
     61:   PetscScalar       *gr;
     62:   PetscReal         *cellPhi;
     63:   PetscInt           dim, face, cell, field, dof, cStart, cEnd, nFields;

     65:   PetscFunctionBegin;
     66:   PetscCall(DMGetDimension(dm, &dim));
     67:   PetscCall(DMGetDS(dm, &prob));
     68:   PetscCall(PetscDSGetNumFields(prob, &nFields));
     69:   PetscCall(PetscDSGetFieldIndex(prob, (PetscObject)fvm, &field));
     70:   PetscCall(PetscDSGetFieldSize(prob, field, &dof));
     71:   PetscCall(DMGetLabel(dm, "ghost", &ghostLabel));
     72:   PetscCall(PetscFVGetLimiter(fvm, &lim));
     73:   PetscCall(VecGetDM(faceGeometry, &dmFace));
     74:   PetscCall(VecGetArrayRead(faceGeometry, &facegeom));
     75:   PetscCall(VecGetDM(cellGeometry, &dmCell));
     76:   PetscCall(VecGetArrayRead(cellGeometry, &cellgeom));
     77:   PetscCall(VecGetArrayRead(locX, &x));
     78:   PetscCall(VecGetDM(grad, &dmGrad));
     79:   PetscCall(VecZeroEntries(grad));
     80:   PetscCall(VecGetArray(grad, &gr));
     81:   /* Reconstruct gradients */
     82:   for (face = fStart; face < fEnd; ++face) {
     83:     const PetscInt  *cells;
     84:     PetscFVFaceGeom *fg;
     85:     PetscScalar     *cx[2];
     86:     PetscScalar     *cgrad[2];
     87:     PetscBool        boundary;
     88:     PetscInt         ghost, c, pd, d, numChildren, numCells;

     90:     PetscCall(DMLabelGetValue(ghostLabel, face, &ghost));
     91:     PetscCall(DMIsBoundaryPoint(dm, face, &boundary));
     92:     PetscCall(DMPlexGetTreeChildren(dm, face, &numChildren, NULL));
     93:     if (ghost >= 0 || boundary || numChildren) continue;
     94:     PetscCall(DMPlexGetSupportSize(dm, face, &numCells));
     95:     PetscCheck(numCells == 2, PETSC_COMM_SELF, PETSC_ERR_PLIB, "facet %" PetscInt_FMT " has %" PetscInt_FMT " support points: expected 2", face, numCells);
     96:     PetscCall(DMPlexGetSupport(dm, face, &cells));
     97:     PetscCall(DMPlexPointLocalRead(dmFace, face, facegeom, &fg));
     98:     for (c = 0; c < 2; ++c) {
     99:       if (nFields > 1) PetscCall(DMPlexPointLocalFieldRead(dm, cells[c], field, x, &cx[c]));
    100:       else PetscCall(DMPlexPointLocalRead(dm, cells[c], x, &cx[c]));
    101:       PetscCall(DMPlexPointGlobalRef(dmGrad, cells[c], gr, &cgrad[c]));
    102:     }
    103:     for (pd = 0; pd < dof; ++pd) {
    104:       PetscScalar delta = cx[1][pd] - cx[0][pd];

    106:       for (d = 0; d < dim; ++d) {
    107:         if (cgrad[0]) cgrad[0][pd * dim + d] += fg->grad[0][d] * delta;
    108:         if (cgrad[1]) cgrad[1][pd * dim + d] -= fg->grad[1][d] * delta;
    109:       }
    110:     }
    111:   }
    112:   /* Limit interior gradients (using cell-based loop because it generalizes better to vector limiters) */
    113:   PetscCall(PetscLimiterGetType(lim, &limType));
    114:   PetscCall(DMPlexGetSimplexOrBoxCells(dm, 0, &cStart, &cEnd));
    115:   PetscCall(DMGetWorkArray(dm, dof, MPIU_REAL, &cellPhi));
    116:   for (cell = (dmGrad && lim) ? cStart : cEnd; cell < cEnd; ++cell) {
    117:     const PetscInt  *faces;
    118:     PetscScalar     *cx;
    119:     PetscFVCellGeom *cg;
    120:     PetscScalar     *cgrad;
    121:     PetscInt         coneSize, f, pd, d;

    123:     PetscCall(DMPlexGetConeSize(dm, cell, &coneSize));
    124:     PetscCall(DMPlexGetCone(dm, cell, &faces));
    125:     if (nFields > 1) PetscCall(DMPlexPointLocalFieldRead(dm, cell, field, x, &cx));
    126:     else PetscCall(DMPlexPointLocalRead(dm, cell, x, &cx));
    127:     PetscCall(DMPlexPointLocalRead(dmCell, cell, cellgeom, &cg));
    128:     PetscCall(DMPlexPointGlobalRef(dmGrad, cell, gr, &cgrad));
    129:     if (!cgrad) continue; /* Unowned overlap cell, we do not compute */
    130:     if (limType) {
    131:       /* Limiter will be minimum value over all neighbors */
    132:       for (d = 0; d < dof; ++d) cellPhi[d] = PETSC_MAX_REAL;
    133:       for (f = 0; f < coneSize; ++f) PetscCall(DMPlexApplyLimiter_Internal(dm, dmCell, lim, dim, dof, cell, nFields > 1 ? field : -1, faces[f], fStart, fEnd, cellPhi, x, cellgeom, cg, cx, cgrad));
    134:     } else {
    135:       for (d = 0; d < dof; ++d) cellPhi[d] = 1.0;
    136:     }
    137:     /* Apply limiter to gradient */
    138:     for (pd = 0; pd < dof; ++pd) /* Scalar limiter applied to each component separately */
    139:       for (d = 0; d < dim; ++d) cgrad[pd * dim + d] *= cellPhi[pd];
    140:   }
    141:   PetscCall(DMRestoreWorkArray(dm, dof, MPIU_REAL, &cellPhi));
    142:   PetscCall(VecRestoreArrayRead(faceGeometry, &facegeom));
    143:   PetscCall(VecRestoreArrayRead(cellGeometry, &cellgeom));
    144:   PetscCall(VecRestoreArrayRead(locX, &x));
    145:   PetscCall(VecRestoreArray(grad, &gr));
    146:   PetscFunctionReturn(PETSC_SUCCESS);
    147: }

    149: /*@
    150:   DMPlexReconstructGradientsFVM - reconstruct the gradient of a vector using a finite volume method.

    152:   Input Parameters:
    153: + dm   - the mesh
    154: - locX - the local representation of the vector

    156:   Output Parameter:
    157: . grad - the global representation of the gradient

    159:   Level: developer

    161: .seealso: [](ch_unstructured), `DM`, `Vec`, `DMPlexGetGradientDM()`
    162: @*/
    163: PetscErrorCode DMPlexReconstructGradientsFVM(DM dm, Vec locX, Vec grad)
    164: {
    165:   PetscDS          prob;
    166:   PetscInt         Nf, f, fStart, fEnd;
    167:   PetscBool        useFVM = PETSC_FALSE;
    168:   PetscFV          fvm    = NULL;
    169:   Vec              faceGeometryFVM, cellGeometryFVM;
    170:   PetscFVCellGeom *cgeomFVM = NULL;
    171:   PetscFVFaceGeom *fgeomFVM = NULL;
    172:   DM               dmGrad   = NULL;

    174:   PetscFunctionBegin;
    175:   PetscCall(DMGetDS(dm, &prob));
    176:   PetscCall(PetscDSGetNumFields(prob, &Nf));
    177:   for (f = 0; f < Nf; ++f) {
    178:     PetscObject  obj;
    179:     PetscClassId id;

    181:     PetscCall(PetscDSGetDiscretization(prob, f, &obj));
    182:     PetscCall(PetscObjectGetClassId(obj, &id));
    183:     if (id == PETSCFV_CLASSID) {
    184:       useFVM = PETSC_TRUE;
    185:       fvm    = (PetscFV)obj;
    186:     }
    187:   }
    188:   PetscCheck(useFVM, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "This dm does not have a finite volume discretization");
    189:   PetscCall(DMPlexGetDataFVM(dm, fvm, &cellGeometryFVM, &faceGeometryFVM, &dmGrad));
    190:   PetscCheck(dmGrad, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "This dm's finite volume discretization does not reconstruct gradients");
    191:   PetscCall(VecGetArrayRead(faceGeometryFVM, (const PetscScalar **)&fgeomFVM));
    192:   PetscCall(VecGetArrayRead(cellGeometryFVM, (const PetscScalar **)&cgeomFVM));
    193:   PetscCall(DMPlexGetHeightStratum(dm, 1, &fStart, &fEnd));
    194:   PetscCall(DMPlexReconstructGradients_Internal(dm, fvm, fStart, fEnd, faceGeometryFVM, cellGeometryFVM, locX, grad));
    195:   PetscFunctionReturn(PETSC_SUCCESS);
    196: }