Date: 2022-03-31T04:47:32+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,
      8:                                                   PetscReal *cellPhi, const PetscScalar *x, const PetscScalar *cellgeom, const PetscFVCellGeom *cg, const PetscScalar *cx, const PetscScalar *cgrad)
      9: {
     10:   const PetscInt *children;
     11:   PetscInt        numChildren;

     13:   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) {
     21:         DMPlexApplyLimiter_Internal(dm,dmCell,lim,dim,dof,cell,field,childFace,fStart,fEnd,cellPhi,x,cellgeom,cg,cx,cgrad);
     22:       }
     23:     }
     24:   } else {
     25:     PetscScalar     *ncx;
     26:     PetscFVCellGeom *ncg;
     27:     const PetscInt  *fcells;
     28:     PetscInt         ncell, d;
     29:     PetscReal        v[3];

     31:     DMPlexGetSupport(dm, face, &fcells);
     32:     ncell = cell == fcells[0] ? fcells[1] : fcells[0];
     33:     if (field >= 0) {
     34:       DMPlexPointLocalFieldRead(dm, ncell, field, x, &ncx);
     35:     } else {
     36:       DMPlexPointLocalRead(dm, ncell, x, &ncx);
     37:     }
     38:     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 phi, flim = 0.5 * PetscRealPart(ncx[d] - cx[d]) / denom;

     45:       PetscLimiterLimit(lim, flim, &phi);
     46:       cellPhi[d] = PetscMin(cellPhi[d], phi);
     47:     }
     48:   }
     49:   return 0;
     50: }

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

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

     87:     DMLabelGetValue(ghostLabel, face, &ghost);
     88:     DMIsBoundaryPoint(dm, face, &boundary);
     89:     DMPlexGetTreeChildren(dm, face, &numChildren, NULL);
     90:     if (ghost >= 0 || boundary || numChildren) continue;
     91:     DMPlexGetSupportSize(dm, face, &numCells);
     93:     DMPlexGetSupport(dm, face, &cells);
     94:     DMPlexPointLocalRead(dmFace, face, facegeom, &fg);
     95:     for (c = 0; c < 2; ++c) {
     96:       if (nFields > 1) {
     97:         DMPlexPointLocalFieldRead(dm, cells[c], field, x, &cx[c]);
     98:       } else {
     99:         DMPlexPointLocalRead(dm, cells[c], x, &cx[c]);
    100:       }
    101:       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:   DMPlexGetSimplexOrBoxCells(dm, 0, &cStart, &cEnd);
    114:   DMGetWorkArray(dm, dof, MPIU_REAL, &cellPhi);
    115:   for (cell = (dmGrad && lim) ? cStart : cEnd; cell < cEnd; ++cell) {
    116:     const PetscInt        *faces;
    117:     PetscScalar           *cx;
    118:     PetscFVCellGeom       *cg;
    119:     PetscScalar           *cgrad;
    120:     PetscInt               coneSize, f, pd, d;

    122:     DMPlexGetConeSize(dm, cell, &coneSize);
    123:     DMPlexGetCone(dm, cell, &faces);
    124:     if (nFields > 1) {
    125:       DMPlexPointLocalFieldRead(dm, cell, field, x, &cx);
    126:     }
    127:     else {
    128:       DMPlexPointLocalRead(dm, cell, x, &cx);
    129:     }
    130:     DMPlexPointLocalRead(dmCell, cell, cellgeom, &cg);
    131:     DMPlexPointGlobalRef(dmGrad, cell, gr, &cgrad);
    132:     if (!cgrad) continue; /* Unowned overlap cell, we do not compute */
    133:     /* Limiter will be minimum value over all neighbors */
    134:     for (d = 0; d < dof; ++d) cellPhi[d] = PETSC_MAX_REAL;
    135:     for (f = 0; f < coneSize; ++f) {
    136:       DMPlexApplyLimiter_Internal(dm,dmCell,lim,dim,dof,cell,nFields > 1 ? field : -1,faces[f],fStart,fEnd,cellPhi,x,cellgeom,cg,cx,cgrad);
    137:     }
    138:     /* Apply limiter to gradient */
    139:     for (pd = 0; pd < dof; ++pd)
    140:       /* Scalar limiter applied to each component separately */
    141:       for (d = 0; d < dim; ++d) cgrad[pd*dim+d] *= cellPhi[pd];
    142:   }
    143:   DMRestoreWorkArray(dm, dof, MPIU_REAL, &cellPhi);
    144:   VecRestoreArrayRead(faceGeometry, &facegeom);
    145:   VecRestoreArrayRead(cellGeometry, &cellgeom);
    146:   VecRestoreArrayRead(locX, &x);
    147:   VecRestoreArray(grad, &gr);
    148:   return 0;
    149: }

    151: /*@
    152:   DMPlexReconstructGradientsFVM - reconstruct the gradient of a vector using a finite volume method.

    154:   Input Parameters:
    155: + dm - the mesh
    156: - locX - the local representation of the vector

    158:   Output Parameter:
    159: . grad - the global representation of the gradient

    161:   Level: developer

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

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

    182:     PetscDSGetDiscretization(prob, f, &obj);
    183:     PetscObjectGetClassId(obj, &id);
    184:     if (id == PETSCFV_CLASSID) {useFVM = PETSC_TRUE; fvm = (PetscFV) obj;}
    185:   }
    187:   DMPlexGetDataFVM(dm, fvm, &cellGeometryFVM, &faceGeometryFVM, &dmGrad);
    189:   VecGetArrayRead(faceGeometryFVM, (const PetscScalar **) &fgeomFVM);
    190:   VecGetArrayRead(cellGeometryFVM, (const PetscScalar **) &cgeomFVM);
    191:   DMPlexGetHeightStratum(dm, 1, &fStart, &fEnd);
    192:   DMPlexReconstructGradients_Internal(dm, fvm, fStart, fEnd, faceGeometryFVM, cellGeometryFVM, locX, grad);
    193:   return 0;
    194: }