Actual source code: plexfvm.c

petsc-master 2020-08-10
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  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;
 12:   PetscErrorCode  ierr;

 15:   DMPlexGetTreeChildren(dm,face,&numChildren,&children);
 16:   if (numChildren) {
 17:     PetscInt c;

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

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

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

 47:       PetscLimiterLimit(lim, flim, &phi);
 48:       cellPhi[d] = PetscMin(cellPhi[d], phi);
 49:     }
 50:   }
 51:   return(0);
 52: }

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

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

 91:     DMLabelGetValue(ghostLabel, face, &ghost);
 92:     DMIsBoundaryPoint(dm, face, &boundary);
 93:     DMPlexGetTreeChildren(dm, face, &numChildren, NULL);
 94:     if (ghost >= 0 || boundary || numChildren) continue;
 95:     DMPlexGetSupportSize(dm, face, &numCells);
 96:     if (numCells != 2) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_PLIB, "facet %d has %d support points: expected 2",face,numCells);
 97:     DMPlexGetSupport(dm, face, &cells);
 98:     DMPlexPointLocalRead(dmFace, face, facegeom, &fg);
 99:     for (c = 0; c < 2; ++c) {
100:       if (nFields > 1) {
101:         DMPlexPointLocalFieldRead(dm, cells[c], field, x, &cx[c]);
102:       } else {
103:         DMPlexPointLocalRead(dm, cells[c], x, &cx[c]);
104:       }
105:       DMPlexPointGlobalRef(dmGrad, cells[c], gr, &cgrad[c]);
106:     }
107:     for (pd = 0; pd < dof; ++pd) {
108:       PetscScalar delta = cx[1][pd] - cx[0][pd];

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

126:     DMPlexGetConeSize(dm, cell, &coneSize);
127:     DMPlexGetCone(dm, cell, &faces);
128:     if (nFields > 1) {
129:       DMPlexPointLocalFieldRead(dm, cell, field, x, &cx);
130:     }
131:     else {
132:       DMPlexPointLocalRead(dm, cell, x, &cx);
133:     }
134:     DMPlexPointLocalRead(dmCell, cell, cellgeom, &cg);
135:     DMPlexPointGlobalRef(dmGrad, cell, gr, &cgrad);
136:     if (!cgrad) continue; /* Unowned overlap cell, we do not compute */
137:     /* Limiter will be minimum value over all neighbors */
138:     for (d = 0; d < dof; ++d) cellPhi[d] = PETSC_MAX_REAL;
139:     for (f = 0; f < coneSize; ++f) {
140:       DMPlexApplyLimiter_Internal(dm,dmCell,lim,dim,dof,cell,nFields > 1 ? field : -1,faces[f],fStart,fEnd,cellPhi,x,cellgeom,cg,cx,cgrad);
141:     }
142:     /* Apply limiter to gradient */
143:     for (pd = 0; pd < dof; ++pd)
144:       /* Scalar limiter applied to each component separately */
145:       for (d = 0; d < dim; ++d) cgrad[pd*dim+d] *= cellPhi[pd];
146:   }
147:   DMRestoreWorkArray(dm, dof, MPIU_REAL, &cellPhi);
148:   VecRestoreArrayRead(faceGeometry, &facegeom);
149:   VecRestoreArrayRead(cellGeometry, &cellgeom);
150:   VecRestoreArrayRead(locX, &x);
151:   VecRestoreArray(grad, &gr);
152:   return(0);
153: }

155: /*@
156:   DMPlexReconstructGradientsFVM - reconstruct the gradient of a vector using a finite volume method.

158:   Input Parameters:
159: + dm - the mesh
160: - locX - the local representation of the vector

162:   Output Parameter:
163: . grad - the global representation of the gradient

165:   Level: developer

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

182:   DMGetDS(dm, &prob);
183:   PetscDSGetNumFields(prob, &Nf);
184:   for (f = 0; f < Nf; ++f) {
185:     PetscObject  obj;
186:     PetscClassId id;

188:     PetscDSGetDiscretization(prob, f, &obj);
189:     PetscObjectGetClassId(obj, &id);
190:     if (id == PETSCFV_CLASSID) {useFVM = PETSC_TRUE; fvm = (PetscFV) obj;}
191:   }
192:   if (!useFVM) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"This dm does not have a finite volume discretization");
193:   DMPlexGetDataFVM(dm, fvm, &cellGeometryFVM, &faceGeometryFVM, &dmGrad);
194:   if (!dmGrad) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"This dm's finite volume discretization does not reconstruct gradients");
195:   VecGetArrayRead(faceGeometryFVM, (const PetscScalar **) &fgeomFVM);
196:   VecGetArrayRead(cellGeometryFVM, (const PetscScalar **) &cgeomFVM);
197:   DMPlexGetHeightStratum(dm, 1, &fStart, &fEnd);
198:   DMPlexReconstructGradients_Internal(dm, fvm, fStart, fEnd, faceGeometryFVM, cellGeometryFVM, locX, grad);
199:   return(0);
200: }