Esempio n. 1
0
/*@
  DMPlexTSComputeBoundary - Insert the essential boundary values for the local input X and/or its time derivative X_t using pointwise functions specified by the user

  Input Parameters:
+ dm - The mesh
. t - The time
. locX  - Local solution
. locX_t - Local solution time derivative, or NULL
- user - The user context

  Level: developer

.seealso: DMPlexComputeJacobianActionFEM()
@*/
PetscErrorCode DMPlexTSComputeBoundary(DM dm, PetscReal time, Vec locX, Vec locX_t, void *user)
{
  DM             plex;
  Vec            faceGeometryFVM = NULL;
  PetscInt       Nf, f;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = DMTSConvertPlex(dm, &plex, PETSC_TRUE);CHKERRQ(ierr);
  ierr = DMGetNumFields(plex, &Nf);CHKERRQ(ierr);
  if (!locX_t) {
    /* This is the RHS part */
    for (f = 0; f < Nf; f++) {
      PetscObject  obj;
      PetscClassId id;

      ierr = DMGetField(plex, f, &obj);CHKERRQ(ierr);
      ierr = PetscObjectGetClassId(obj, &id);CHKERRQ(ierr);
      if (id == PETSCFV_CLASSID) {
        ierr = DMPlexSNESGetGeometryFVM(plex, &faceGeometryFVM, NULL, NULL);CHKERRQ(ierr);
        break;
      }
    }
  }
  ierr = DMPlexInsertBoundaryValues(plex, PETSC_TRUE, locX, time, faceGeometryFVM, NULL, NULL);CHKERRQ(ierr);
  /* TODO: locX_t */
  ierr = DMDestroy(&plex);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
Esempio n. 2
0
PetscErrorCode CreatePressureNullSpace(DM dm, AppCtx *user, MatNullSpace *nullSpace)
{
  Vec            vec, localVec;
  PetscErrorCode ierr;

  PetscFunctionBeginUser;
  ierr = DMGetGlobalVector(dm, &vec);CHKERRQ(ierr);
  ierr = DMGetLocalVector(dm, &localVec);CHKERRQ(ierr);
  ierr = VecSet(vec,  0.0);CHKERRQ(ierr);
  /* Put a constant in for all pressures
     Could change this to project the constant function onto the pressure space (when that is finished) */
  {
    PetscSection section;
    PetscInt     pStart, pEnd, p;
    PetscScalar  *a;

    ierr = DMGetDefaultSection(dm, &section);CHKERRQ(ierr);
    ierr = PetscSectionGetChart(section, &pStart, &pEnd);CHKERRQ(ierr);
    ierr = VecGetArray(localVec, &a);CHKERRQ(ierr);
    for (p = pStart; p < pEnd; ++p) {
      PetscInt fDim, off, d;

      ierr = PetscSectionGetFieldDof(section, p, 1, &fDim);CHKERRQ(ierr);
      ierr = PetscSectionGetFieldOffset(section, p, 1, &off);CHKERRQ(ierr);
      for (d = 0; d < fDim; ++d) a[off+d] = 1.0;
    }
    ierr = VecRestoreArray(localVec, &a);CHKERRQ(ierr);
  }
  ierr = DMLocalToGlobalBegin(dm, localVec, INSERT_VALUES, vec);CHKERRQ(ierr);
  ierr = DMLocalToGlobalEnd(dm, localVec, INSERT_VALUES, vec);CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(dm, &localVec);CHKERRQ(ierr);
  ierr = VecNormalize(vec, NULL);CHKERRQ(ierr);
  if (user->debug) {
    ierr = PetscPrintf(PetscObjectComm((PetscObject)dm), "Pressure Null Space\n");CHKERRQ(ierr);
    ierr = VecView(vec, PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
  }
  ierr = MatNullSpaceCreate(PetscObjectComm((PetscObject)dm), PETSC_FALSE, 1, &vec, nullSpace);CHKERRQ(ierr);
  ierr = DMRestoreGlobalVector(dm, &vec);CHKERRQ(ierr);
  /* New style for field null spaces */
  {
    PetscObject  pressure;
    MatNullSpace nullSpacePres;

    ierr = DMGetField(dm, 1, &pressure);CHKERRQ(ierr);
    ierr = MatNullSpaceCreate(PetscObjectComm(pressure), PETSC_TRUE, 0, NULL, &nullSpacePres);CHKERRQ(ierr);
    ierr = PetscObjectCompose(pressure, "nullspace", (PetscObject) nullSpacePres);CHKERRQ(ierr);
    ierr = MatNullSpaceDestroy(&nullSpacePres);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}
Esempio n. 3
0
/*@C
  DMPlexTSSetRHSFunctionLocal - set a local residual evaluation function

  Logically Collective

  Input Arguments:
+ dm      - DM to associate callback with
. riemann - Riemann solver
- ctx     - optional context for Riemann solve

  Calling sequence for riemann:

$ riemann(const PetscReal x[], const PetscReal n[], const PetscScalar uL[], const PetscScalar uR[], PetscScalar flux[], void *ctx)

+ x    - The coordinates at a point on the interface
. n    - The normal vector to the interface
. uL   - The state vector to the left of the interface
. uR   - The state vector to the right of the interface
. flux - output array of flux through the interface
- ctx  - optional user context

  Level: beginner

.seealso: DMTSSetRHSFunctionLocal()
@*/
PetscErrorCode DMPlexTSSetRHSFunctionLocal(DM dm, void (*riemann)(const PetscReal x[], const PetscReal n[], const PetscScalar uL[], const PetscScalar uR[], PetscScalar flux[], void *ctx), void *ctx)
{
  DMTS           dmts;
  DMTS_Plex     *dmplexts;
  PetscFV        fvm;
  PetscInt       Nf;
  PetscBool      computeGradients;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm, DM_CLASSID, 1);
  ierr = DMGetDMTSWrite(dm, &dmts);CHKERRQ(ierr);
  ierr = DMPlexTSGetContext(dm, dmts, &dmplexts);CHKERRQ(ierr);
  dmplexts->riemann             = riemann;
  dmplexts->rhsfunctionlocalctx = ctx;
  ierr = DMGetNumFields(dm, &Nf);CHKERRQ(ierr);
  ierr = DMGetField(dm, 0, (PetscObject *) &fvm);CHKERRQ(ierr);
  ierr = DMPlexTSSetupGeometry(dm, fvm, dmplexts);CHKERRQ(ierr);
  ierr = PetscFVGetComputeGradients(fvm, &computeGradients);CHKERRQ(ierr);
  if (computeGradients) {ierr = DMPlexTSSetupGradient(dm, fvm, dmplexts);CHKERRQ(ierr);}
  ierr = DMTSSetRHSFunction(dm, TSComputeRHSFunction_DMPlex, dmplexts);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
Esempio n. 4
0
int main(int argc,char **args)
{
  Mat            Amat;
  PetscErrorCode ierr;
  SNES           snes;
  KSP            ksp;
  MPI_Comm       comm;
  PetscMPIInt    npe,rank;
  PetscLogStage  stage[7];
  PetscBool      test_nonzero_cols=PETSC_FALSE,use_nearnullspace=PETSC_TRUE;
  Vec            xx,bb;
  PetscInt       iter,i,N,dim=3,cells[3]={1,1,1},max_conv_its,local_sizes[7],run_type=1;
  DM             dm,distdm,basedm;
  PetscBool      flg;
  char           convType[256];
  PetscReal      Lx,mdisp[10],err[10];
  const char * const options[10] = {"-ex56_dm_refine 0",
                                    "-ex56_dm_refine 1",
                                    "-ex56_dm_refine 2",
                                    "-ex56_dm_refine 3",
                                    "-ex56_dm_refine 4",
                                    "-ex56_dm_refine 5",
                                    "-ex56_dm_refine 6",
                                    "-ex56_dm_refine 7",
                                    "-ex56_dm_refine 8",
                                    "-ex56_dm_refine 9"};
  PetscFunctionBeginUser;
  ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
  comm = PETSC_COMM_WORLD;
  ierr = MPI_Comm_rank(comm, &rank);CHKERRQ(ierr);
  ierr = MPI_Comm_size(comm, &npe);CHKERRQ(ierr);
  /* options */
  ierr = PetscOptionsBegin(comm,NULL,"3D bilinear Q1 elasticity options","");CHKERRQ(ierr);
  {
    i = 3;
    ierr = PetscOptionsIntArray("-cells", "Number of (flux tube) processor in each dimension", "ex56.c", cells, &i, NULL);CHKERRQ(ierr);

    Lx = 1.; /* or ne for rod */
    max_conv_its = 3;
    ierr = PetscOptionsInt("-max_conv_its","Number of iterations in convergence study","",max_conv_its,&max_conv_its,NULL);CHKERRQ(ierr);
    if (max_conv_its<=0 || max_conv_its>7) SETERRQ1(PETSC_COMM_WORLD, PETSC_ERR_USER, "Bad number of iterations for convergence test (%D)",max_conv_its);
    ierr = PetscOptionsReal("-lx","Length of domain","",Lx,&Lx,NULL);CHKERRQ(ierr);
    ierr = PetscOptionsReal("-alpha","material coefficient inside circle","",s_soft_alpha,&s_soft_alpha,NULL);CHKERRQ(ierr);
    ierr = PetscOptionsBool("-test_nonzero_cols","nonzero test","",test_nonzero_cols,&test_nonzero_cols,NULL);CHKERRQ(ierr);
    ierr = PetscOptionsBool("-use_mat_nearnullspace","MatNearNullSpace API test","",use_nearnullspace,&use_nearnullspace,NULL);CHKERRQ(ierr);
    ierr = PetscOptionsInt("-run_type","0: twisting load on cantalever, 1: 3rd order accurate convergence test","",run_type,&run_type,NULL);CHKERRQ(ierr);
    i = 3;
    ierr = PetscOptionsInt("-mat_block_size","","",i,&i,&flg);CHKERRQ(ierr);
    if (!flg || i!=3) SETERRQ2(PETSC_COMM_WORLD, PETSC_ERR_USER, "'-mat_block_size 3' must be set (%D) and = 3 (%D)",flg,flg? i : 3);
  }
  ierr = PetscOptionsEnd();CHKERRQ(ierr);
  ierr = PetscLogStageRegister("Mesh Setup", &stage[6]);CHKERRQ(ierr);
  ierr = PetscLogStageRegister("1st Setup", &stage[0]);CHKERRQ(ierr);
  ierr = PetscLogStageRegister("1st Solve", &stage[1]);CHKERRQ(ierr);

  /* create DM, Plex calls DMSetup */
  ierr = PetscLogStagePush(stage[6]);CHKERRQ(ierr);
  ierr = DMPlexCreateHexBoxMesh(comm, dim, cells, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, DM_BOUNDARY_NONE, &dm);CHKERRQ(ierr);
  {
    DMLabel         label;
    IS              is;
    ierr = DMCreateLabel(dm, "boundary");CHKERRQ(ierr);
    ierr = DMGetLabel(dm, "boundary", &label);CHKERRQ(ierr);
    ierr = DMPlexMarkBoundaryFaces(dm, label);CHKERRQ(ierr);
    if (run_type==0) {
      ierr = DMGetStratumIS(dm, "boundary", 1,  &is);CHKERRQ(ierr);
      ierr = DMCreateLabel(dm,"Faces");CHKERRQ(ierr);
      if (is) {
        PetscInt        d, f, Nf;
        const PetscInt *faces;
        PetscInt        csize;
        PetscSection    cs;
        Vec             coordinates ;
        DM              cdm;
        ierr = ISGetLocalSize(is, &Nf);CHKERRQ(ierr);
        ierr = ISGetIndices(is, &faces);CHKERRQ(ierr);
        ierr = DMGetCoordinatesLocal(dm, &coordinates);CHKERRQ(ierr);
        ierr = DMGetCoordinateDM(dm, &cdm);CHKERRQ(ierr);
        ierr = DMGetDefaultSection(cdm, &cs);CHKERRQ(ierr);
        /* Check for each boundary face if any component of its centroid is either 0.0 or 1.0 */
        for (f = 0; f < Nf; ++f) {
          PetscReal   faceCoord;
          PetscInt    b,v;
          PetscScalar *coords = NULL;
          PetscInt    Nv;
          ierr = DMPlexVecGetClosure(cdm, cs, coordinates, faces[f], &csize, &coords);CHKERRQ(ierr);
          Nv   = csize/dim; /* Calculate mean coordinate vector */
          for (d = 0; d < dim; ++d) {
            faceCoord = 0.0;
            for (v = 0; v < Nv; ++v) faceCoord += PetscRealPart(coords[v*dim+d]);
            faceCoord /= Nv;
            for (b = 0; b < 2; ++b) {
              if (PetscAbs(faceCoord - b) < PETSC_SMALL) { /* domain have not been set yet, still [0,1]^3 */
                ierr = DMSetLabelValue(dm, "Faces", faces[f], d*2+b+1);CHKERRQ(ierr);
              }
            }
          }
          ierr = DMPlexVecRestoreClosure(cdm, cs, coordinates, faces[f], &csize, &coords);CHKERRQ(ierr);
        }
        ierr = ISRestoreIndices(is, &faces);CHKERRQ(ierr);
      }
      ierr = ISDestroy(&is);CHKERRQ(ierr);
      ierr = DMGetLabel(dm, "Faces", &label);CHKERRQ(ierr);
      ierr = DMPlexLabelComplete(dm, label);CHKERRQ(ierr);
    }
  }
  {
    PetscInt dimEmbed, i;
    PetscInt nCoords;
    PetscScalar *coords,bounds[] = {0,Lx,-.5,.5,-.5,.5,}; /* x_min,x_max,y_min,y_max */
    Vec coordinates;
    if (run_type==1) {
      for (i = 0; i < 2*dim; i++) bounds[i] = (i%2) ? 1 : 0;
    }
    ierr = DMGetCoordinatesLocal(dm,&coordinates);CHKERRQ(ierr);
    ierr = DMGetCoordinateDim(dm,&dimEmbed);CHKERRQ(ierr);
    if (dimEmbed != dim) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"dimEmbed != dim %D",dimEmbed);CHKERRQ(ierr);
    ierr = VecGetLocalSize(coordinates,&nCoords);CHKERRQ(ierr);
    if (nCoords % dimEmbed) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Coordinate vector the wrong size");CHKERRQ(ierr);
    ierr = VecGetArray(coordinates,&coords);CHKERRQ(ierr);
    for (i = 0; i < nCoords; i += dimEmbed) {
      PetscInt j;
      PetscScalar *coord = &coords[i];
      for (j = 0; j < dimEmbed; j++) {
        coord[j] = bounds[2 * j] + coord[j] * (bounds[2 * j + 1] - bounds[2 * j]);
      }
    }
    ierr = VecRestoreArray(coordinates,&coords);CHKERRQ(ierr);
    ierr = DMSetCoordinatesLocal(dm,coordinates);CHKERRQ(ierr);
  }

  /* convert to p4est, and distribute */

  ierr = PetscOptionsBegin(comm, "", "Mesh conversion options", "DMPLEX");CHKERRQ(ierr);
  ierr = PetscOptionsFList("-dm_type","Convert DMPlex to another format (should not be Plex!)","ex56.c",DMList,DMPLEX,convType,256,&flg);CHKERRQ(ierr);
  ierr = PetscOptionsEnd();
  if (flg) {
    DM newdm;
    ierr = DMConvert(dm,convType,&newdm);CHKERRQ(ierr);
    if (newdm) {
      const char *prefix;
      PetscBool isForest;
      ierr = PetscObjectGetOptionsPrefix((PetscObject)dm,&prefix);CHKERRQ(ierr);
      ierr = PetscObjectSetOptionsPrefix((PetscObject)newdm,prefix);CHKERRQ(ierr);
      ierr = DMIsForest(newdm,&isForest);CHKERRQ(ierr);
      if (isForest) {
      } else SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_USER, "Converted to non Forest?");
      ierr = DMDestroy(&dm);CHKERRQ(ierr);
      dm   = newdm;
    } else SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_USER, "Convert failed?");
  } else {
    /* Plex Distribute mesh over processes */
    ierr = DMPlexDistribute(dm, 0, NULL, &distdm);CHKERRQ(ierr);
    if (distdm) {
      const char *prefix;
      ierr = PetscObjectGetOptionsPrefix((PetscObject)dm,&prefix);CHKERRQ(ierr);
      ierr = PetscObjectSetOptionsPrefix((PetscObject)distdm,prefix);CHKERRQ(ierr);
      ierr = DMDestroy(&dm);CHKERRQ(ierr);
      dm   = distdm;
    }
  }
  ierr = PetscLogStagePop();CHKERRQ(ierr);
  basedm = dm; dm = NULL;

  for (iter=0 ; iter<max_conv_its ; iter++) {
    ierr = PetscLogStagePush(stage[6]);CHKERRQ(ierr);
    /* make new DM */
    ierr = DMClone(basedm, &dm);CHKERRQ(ierr);
    ierr = PetscObjectSetOptionsPrefix((PetscObject) dm, "ex56_");CHKERRQ(ierr);
    ierr = PetscObjectSetName( (PetscObject)dm,"Mesh");CHKERRQ(ierr);
    ierr = PetscOptionsClearValue(NULL,"-ex56_dm_refine");CHKERRQ(ierr);
    ierr = PetscOptionsInsertString(NULL,options[iter]);CHKERRQ(ierr);
    ierr = DMSetFromOptions(dm);CHKERRQ(ierr); /* refinement done here in Plex, p4est */
    /* snes */
    ierr = SNESCreate(comm, &snes);CHKERRQ(ierr);
    ierr = SNESSetDM(snes, dm);CHKERRQ(ierr);
    /* fem */
    {
      const PetscInt Ncomp = dim;
      const PetscInt components[] = {0,1,2};
      const PetscInt Nfid = 1, Npid = 1;
      const PetscInt fid[] = {1}; /* The fixed faces (x=0) */
      const PetscInt pid[] = {2}; /* The faces with loading (x=L_x) */
      PetscFE         fe;
      PetscDS         prob;
      DM              cdm = dm;

      ierr = PetscFECreateDefault(dm, dim, dim, PETSC_FALSE, NULL, PETSC_DECIDE, &fe);CHKERRQ(ierr); /* elasticity */
      ierr = PetscObjectSetName((PetscObject) fe, "deformation");CHKERRQ(ierr);
      /* FEM prob */
      ierr = DMGetDS(dm, &prob);CHKERRQ(ierr);
      ierr = PetscDSSetDiscretization(prob, 0, (PetscObject) fe);CHKERRQ(ierr);
      /* setup problem */
      if (run_type==1) {
        ierr = PetscDSSetJacobian(prob, 0, 0, NULL, NULL, NULL, g3_uu_3d);CHKERRQ(ierr);
        ierr = PetscDSSetResidual(prob, 0, f0_u_x4, f1_u_3d);CHKERRQ(ierr);
      } else {
        ierr = PetscDSSetJacobian(prob, 0, 0, NULL, NULL, NULL, g3_uu_3d_alpha);CHKERRQ(ierr);
        ierr = PetscDSSetResidual(prob, 0, f0_u, f1_u_3d_alpha);CHKERRQ(ierr);
        ierr = PetscDSSetBdResidual(prob, 0, f0_bd_u_3d, f1_bd_u);CHKERRQ(ierr);
      }
      /* bcs */
      if (run_type==1) {
        PetscInt id = 1;
        ierr = DMAddBoundary(dm, DM_BC_ESSENTIAL, "wall", "boundary", 0, 0, NULL, (void (*)()) zero, 1, &id, NULL);CHKERRQ(ierr);
      } else {
        ierr = PetscDSAddBoundary(prob, DM_BC_ESSENTIAL, "fixed", "Faces", 0, Ncomp, components, (void (*)()) zero, Nfid, fid, NULL);CHKERRQ(ierr);
        ierr = PetscDSAddBoundary(prob, DM_BC_NATURAL, "traction", "Faces", 0, Ncomp, components, NULL, Npid, pid, NULL);CHKERRQ(ierr);
      }
      while (cdm) {
        ierr = DMSetDS(cdm,prob);CHKERRQ(ierr);
        ierr = DMGetCoarseDM(cdm, &cdm);CHKERRQ(ierr);
      }
      ierr = PetscFEDestroy(&fe);CHKERRQ(ierr);
    }
    /* vecs & mat */
    ierr = DMCreateGlobalVector(dm,&xx);CHKERRQ(ierr);
    ierr = VecDuplicate(xx, &bb);CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject) bb, "b");CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject) xx, "u");CHKERRQ(ierr);
    ierr = DMCreateMatrix(dm, &Amat);CHKERRQ(ierr);
    ierr = VecGetSize(bb,&N);CHKERRQ(ierr);
    local_sizes[iter] = N;
    ierr = PetscPrintf(PETSC_COMM_WORLD,"[%d]%s %d global equations, %d vertices\n",rank,PETSC_FUNCTION_NAME,N,N/dim);CHKERRQ(ierr);
    if (use_nearnullspace && N/dim > 1) {
      /* Set up the near null space (a.k.a. rigid body modes) that will be used by the multigrid preconditioner */
      DM           subdm;
      MatNullSpace nearNullSpace;
      PetscInt     fields = 0;
      PetscObject  deformation;
      ierr = DMCreateSubDM(dm, 1, &fields, NULL, &subdm);CHKERRQ(ierr);
      ierr = DMPlexCreateRigidBody(subdm, &nearNullSpace);CHKERRQ(ierr);
      ierr = DMGetField(dm, 0, &deformation);CHKERRQ(ierr);
      ierr = PetscObjectCompose(deformation, "nearnullspace", (PetscObject) nearNullSpace);CHKERRQ(ierr);
      ierr = DMDestroy(&subdm);CHKERRQ(ierr);
      ierr = MatNullSpaceDestroy(&nearNullSpace);CHKERRQ(ierr); /* created by DM and destroyed by Mat */
    }
    ierr = DMPlexSetSNESLocalFEM(dm,NULL,NULL,NULL);CHKERRQ(ierr);
    ierr = SNESSetJacobian(snes, Amat, Amat, NULL, NULL);CHKERRQ(ierr);
    ierr = SNESSetFromOptions(snes);CHKERRQ(ierr);
    ierr = DMSetUp(dm);CHKERRQ(ierr);
    ierr = PetscLogStagePop();CHKERRQ(ierr);
    ierr = PetscLogStagePush(stage[0]);CHKERRQ(ierr);
    /* ksp */
    ierr = SNESGetKSP(snes, &ksp);CHKERRQ(ierr);
    ierr = KSPSetComputeSingularValues(ksp,PETSC_TRUE);CHKERRQ(ierr);
    /* test BCs */
    ierr = VecZeroEntries(xx);CHKERRQ(ierr);
    if (test_nonzero_cols) {
      if (rank==0) ierr = VecSetValue(xx,0,1.0,INSERT_VALUES);CHKERRQ(ierr);
      ierr = VecAssemblyBegin(xx);CHKERRQ(ierr);
      ierr = VecAssemblyEnd(xx);CHKERRQ(ierr);
    }
    ierr = VecZeroEntries(bb);CHKERRQ(ierr);
    ierr = VecGetSize(bb,&i);CHKERRQ(ierr);
    local_sizes[iter] = i;
    ierr = PetscPrintf(PETSC_COMM_WORLD,"[%d]%s %d equations in vector, %d vertices\n",rank,PETSC_FUNCTION_NAME,i,i/dim);CHKERRQ(ierr);
    /* setup solver, dummy solve to really setup */
    if (0) {
      ierr = KSPSetTolerances(ksp,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,1);CHKERRQ(ierr);
      ierr = SNESSolve(snes, bb, xx);CHKERRQ(ierr);
      ierr = KSPSetTolerances(ksp,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,50);CHKERRQ(ierr);
      ierr = VecZeroEntries(xx);CHKERRQ(ierr);
    }
    ierr = PetscLogStagePop();CHKERRQ(ierr);
    /* solve */
    ierr = PetscLogStagePush(stage[1]);CHKERRQ(ierr);
    ierr = SNESSolve(snes, bb, xx);CHKERRQ(ierr);
    ierr = PetscLogStagePop();CHKERRQ(ierr);
    ierr = VecNorm(xx,NORM_INFINITY,&mdisp[iter]);CHKERRQ(ierr);
    ierr = DMViewFromOptions(dm, NULL, "-dm_view");CHKERRQ(ierr);
    {
      PetscViewer       viewer = NULL;
      PetscViewerFormat fmt;
      ierr = PetscOptionsGetViewer(comm,"ex56_","-vec_view",&viewer,&fmt,&flg);CHKERRQ(ierr);
      if (flg) {
        ierr = PetscViewerPushFormat(viewer,fmt);CHKERRQ(ierr);
        ierr = VecView(xx,viewer);CHKERRQ(ierr);
        ierr = VecView(bb,viewer);CHKERRQ(ierr);
        ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
      }
      ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
    }
    /* Free work space */
    ierr = DMDestroy(&dm);CHKERRQ(ierr);
    ierr = SNESDestroy(&snes);CHKERRQ(ierr);
    ierr = VecDestroy(&xx);CHKERRQ(ierr);
    ierr = VecDestroy(&bb);CHKERRQ(ierr);
    ierr = MatDestroy(&Amat);CHKERRQ(ierr);
  }
  ierr = DMDestroy(&basedm);CHKERRQ(ierr);
  if (run_type==1) {
    err[0] = 59.975208 - mdisp[0]; /* error with what I think is the exact solution */
  } else {
    err[0] = 171.038 - mdisp[0];
  }
  for (iter=1 ; iter<max_conv_its ; iter++) {
    if (run_type==1) {
      err[iter] = 59.975208 - mdisp[iter];
    } else {
      err[iter] = 171.038 - mdisp[iter];
    }
    PetscPrintf(PETSC_COMM_WORLD,"[%d]%s %D) N=%12D, max displ=%9.7e, disp diff=%9.2e, error=%4.3e, rate=%3.2g\n",
                rank,PETSC_FUNCTION_NAME,iter,local_sizes[iter],mdisp[iter],
                mdisp[iter]-mdisp[iter-1],err[iter],log(err[iter-1]/err[iter])/log(2.));
  }

  ierr = PetscFinalize();
  return ierr;
}
Esempio n. 5
0
static PetscErrorCode TSComputeRHSFunction_DMPlex(TS ts, PetscReal time, Vec X, Vec F, void *ctx)
{
  DM                 dm;
  DMTS_Plex         *dmplexts = (DMTS_Plex *) ctx;
  void             (*riemann)(const PetscReal[], const PetscReal[], const PetscScalar[], const PetscScalar[], PetscScalar[], void *) = dmplexts->riemann;
  PetscFV            fvm;
  PetscLimiter       lim;
  Vec                faceGeometry = dmplexts->facegeom;
  Vec                cellGeometry = dmplexts->cellgeom;
  Vec                Grad = NULL, locGrad, locX;
  DM                 dmFace, dmCell;
  DMLabel            ghostLabel;
  PetscCellGeometry  fgeom, cgeom;
  const PetscScalar *facegeom, *cellgeom, *x, *lgrad;
  PetscScalar       *grad, *f, *uL, *uR, *fluxL, *fluxR;
  PetscReal         *centroid, *normal, *vol, *cellPhi;
  PetscBool          computeGradients;
  PetscInt           Nf, dim, pdim, fStart, fEnd, numFaces = 0, face, iface, cell, cStart, cEnd, cEndInterior;
  PetscErrorCode     ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ts,TS_CLASSID,1);
  PetscValidHeaderSpecific(X,VEC_CLASSID,3);
  PetscValidHeaderSpecific(F,VEC_CLASSID,5);
  ierr = TSGetDM(ts, &dm);CHKERRQ(ierr);
  ierr = DMGetLocalVector(dm, &locX);CHKERRQ(ierr);
  ierr = VecZeroEntries(locX);CHKERRQ(ierr);
  ierr = DMGlobalToLocalBegin(dm, X, INSERT_VALUES, locX);CHKERRQ(ierr);
  ierr = DMGlobalToLocalEnd(dm, X, INSERT_VALUES, locX);CHKERRQ(ierr);
  ierr = VecZeroEntries(F);CHKERRQ(ierr);
  ierr = DMPlexGetDimension(dm, &dim);CHKERRQ(ierr);
  ierr = DMGetNumFields(dm, &Nf);CHKERRQ(ierr);
  ierr = DMGetField(dm, 0, (PetscObject *) &fvm);CHKERRQ(ierr);
  ierr = PetscFVGetLimiter(fvm, &lim);CHKERRQ(ierr);
  ierr = PetscFVGetNumComponents(fvm, &pdim);CHKERRQ(ierr);
  ierr = PetscFVGetComputeGradients(fvm, &computeGradients);CHKERRQ(ierr);
  if (computeGradients) {
    ierr = DMGetGlobalVector(dmplexts->dmGrad, &Grad);CHKERRQ(ierr);
    ierr = VecZeroEntries(Grad);CHKERRQ(ierr);
    ierr = VecGetArray(Grad, &grad);CHKERRQ(ierr);
  }
  ierr = DMPlexGetLabel(dm, "ghost", &ghostLabel);CHKERRQ(ierr);
  ierr = DMPlexGetHeightStratum(dm, 1, &fStart, &fEnd);CHKERRQ(ierr);
  ierr = VecGetDM(faceGeometry, &dmFace);CHKERRQ(ierr);
  ierr = VecGetDM(cellGeometry, &dmCell);CHKERRQ(ierr);
  ierr = VecGetArrayRead(faceGeometry, &facegeom);CHKERRQ(ierr);
  ierr = VecGetArrayRead(cellGeometry, &cellgeom);CHKERRQ(ierr);
  ierr = VecGetArrayRead(locX, &x);CHKERRQ(ierr);
  /* Count faces and reconstruct gradients */
  for (face = fStart; face < fEnd; ++face) {
    const PetscInt    *cells;
    const FaceGeom    *fg;
    const PetscScalar *cx[2];
    PetscScalar       *cgrad[2];
    PetscBool          boundary;
    PetscInt           ghost, c, pd, d;

    ierr = DMLabelGetValue(ghostLabel, face, &ghost);CHKERRQ(ierr);
    if (ghost >= 0) continue;
    ++numFaces;
    if (!computeGradients) continue;
    ierr = DMPlexIsBoundaryPoint(dm, face, &boundary);CHKERRQ(ierr);
    if (boundary) continue;
    ierr = DMPlexGetSupport(dm, face, &cells);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dmFace, face, facegeom, &fg);CHKERRQ(ierr);
    for (c = 0; c < 2; ++c) {
      ierr = DMPlexPointLocalRead(dm, cells[c], x, &cx[c]);CHKERRQ(ierr);
      ierr = DMPlexPointGlobalRef(dmplexts->dmGrad, cells[c], grad, &cgrad[c]);CHKERRQ(ierr);
    }
    for (pd = 0; pd < pdim; ++pd) {
      PetscScalar delta = cx[1][pd] - cx[0][pd];

      for (d = 0; d < dim; ++d) {
        if (cgrad[0]) cgrad[0][pd*dim+d] += fg->grad[0][d] * delta;
        if (cgrad[1]) cgrad[1][pd*dim+d] -= fg->grad[1][d] * delta;
      }
    }
  }
  /* Limit interior gradients (using cell-based loop because it generalizes better to vector limiters) */
  ierr = DMPlexGetHeightStratum(dm, 0, &cStart, &cEnd);CHKERRQ(ierr);
  ierr = DMPlexGetHybridBounds(dm, &cEndInterior, NULL, NULL, NULL);CHKERRQ(ierr);
  ierr = DMGetWorkArray(dm, pdim, PETSC_REAL, &cellPhi);CHKERRQ(ierr);
  for (cell = computeGradients && lim ? cStart : cEnd; cell < cEndInterior; ++cell) {
    const PetscInt    *faces;
    const PetscScalar *cx;
    const CellGeom    *cg;
    PetscScalar       *cgrad;
    PetscInt           coneSize, f, pd, d;

    ierr = DMPlexGetConeSize(dm, cell, &coneSize);CHKERRQ(ierr);
    ierr = DMPlexGetCone(dm, cell, &faces);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dm, cell, x, &cx);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dmCell, cell, cellgeom, &cg);CHKERRQ(ierr);
    ierr = DMPlexPointGlobalRef(dmplexts->dmGrad, cell, grad, &cgrad);CHKERRQ(ierr);
    if (!cgrad) continue; /* Unowned overlap cell, we do not compute */
    /* Limiter will be minimum value over all neighbors */
    for (d = 0; d < pdim; ++d) cellPhi[d] = PETSC_MAX_REAL;
    for (f = 0; f < coneSize; ++f) {
      const PetscScalar *ncx;
      const CellGeom    *ncg;
      const PetscInt    *fcells;
      PetscInt           face = faces[f], ncell, ghost;
      PetscReal          v[3];
      PetscBool          boundary;

      ierr = DMLabelGetValue(ghostLabel, face, &ghost);CHKERRQ(ierr);
      ierr = DMPlexIsBoundaryPoint(dm, face, &boundary);CHKERRQ(ierr);
      if ((ghost >= 0) || boundary) continue;
      ierr  = DMPlexGetSupport(dm, face, &fcells);CHKERRQ(ierr);
      ncell = cell == fcells[0] ? fcells[1] : fcells[0];
      ierr  = DMPlexPointLocalRead(dm, ncell, x, &ncx);CHKERRQ(ierr);
      ierr  = DMPlexPointLocalRead(dmCell, ncell, cellgeom, &ncg);CHKERRQ(ierr);
      WaxpyD(dim, -1, cg->centroid, ncg->centroid, v);
      for (d = 0; d < pdim; ++d) {
        /* We use the symmetric slope limited form of Berger, Aftosmis, and Murman 2005 */
        PetscReal phi, flim = 0.5 * PetscRealPart(ncx[d] - cx[d]) / DotD(dim, &cgrad[d*dim], v);

        ierr = PetscLimiterLimit(lim, flim, &phi);CHKERRQ(ierr);
        cellPhi[d] = PetscMin(cellPhi[d], phi);
      }
    }
    /* Apply limiter to gradient */
    for (pd = 0; pd < pdim; ++pd)
      /* Scalar limiter applied to each component separately */
      for (d = 0; d < dim; ++d) cgrad[pd*dim+d] *= cellPhi[pd];
  }
  ierr = DMRestoreWorkArray(dm, pdim, PETSC_REAL, &cellPhi);CHKERRQ(ierr);
  ierr = DMPlexInsertBoundaryValuesFVM_Static(dm, fvm, time, locX, Grad, dmplexts);CHKERRQ(ierr);
  if (computeGradients) {
    ierr = VecRestoreArray(Grad, &grad);CHKERRQ(ierr);
    ierr = DMGetLocalVector(dmplexts->dmGrad, &locGrad);CHKERRQ(ierr);
    ierr = DMGlobalToLocalBegin(dmplexts->dmGrad, Grad, INSERT_VALUES, locGrad);CHKERRQ(ierr);
    ierr = DMGlobalToLocalEnd(dmplexts->dmGrad, Grad, INSERT_VALUES, locGrad);CHKERRQ(ierr);
    ierr = DMRestoreGlobalVector(dmplexts->dmGrad, &Grad);CHKERRQ(ierr);
    ierr = VecGetArrayRead(locGrad, &lgrad);CHKERRQ(ierr);
  }
  ierr = PetscMalloc7(numFaces*dim,&centroid,numFaces*dim,&normal,numFaces*2,&vol,numFaces*pdim,&uL,numFaces*pdim,&uR,numFaces*pdim,&fluxL,numFaces*pdim,&fluxR);CHKERRQ(ierr);
  /* Read out values */
  for (face = fStart, iface = 0; face < fEnd; ++face) {
    const PetscInt    *cells;
    const FaceGeom    *fg;
    const CellGeom    *cgL, *cgR;
    const PetscScalar *xL, *xR, *gL, *gR;
    PetscInt           ghost, d;

    ierr = DMLabelGetValue(ghostLabel, face, &ghost);CHKERRQ(ierr);
    if (ghost >= 0) continue;
    ierr = DMPlexPointLocalRead(dmFace, face, facegeom, &fg);CHKERRQ(ierr);
    ierr = DMPlexGetSupport(dm, face, &cells);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dmCell, cells[0], cellgeom, &cgL);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dmCell, cells[1], cellgeom, &cgR);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dm, cells[0], x, &xL);CHKERRQ(ierr);
    ierr = DMPlexPointLocalRead(dm, cells[1], x, &xR);CHKERRQ(ierr);
    if (computeGradients) {
      PetscReal dxL[3], dxR[3];

      ierr = DMPlexPointLocalRead(dmplexts->dmGrad, cells[0], lgrad, &gL);CHKERRQ(ierr);
      ierr = DMPlexPointLocalRead(dmplexts->dmGrad, cells[1], lgrad, &gR);CHKERRQ(ierr);
      WaxpyD(dim, -1, cgL->centroid, fg->centroid, dxL);
      WaxpyD(dim, -1, cgR->centroid, fg->centroid, dxR);
      for (d = 0; d < pdim; ++d) {
        uL[iface*pdim+d] = xL[d] + DotD(dim, &gL[d*dim], dxL);
        uR[iface*pdim+d] = xR[d] + DotD(dim, &gR[d*dim], dxR);
      }
    } else {
      for (d = 0; d < pdim; ++d) {
        uL[iface*pdim+d] = xL[d];
        uR[iface*pdim+d] = xR[d];
      }
    }
    for (d = 0; d < dim; ++d) {
      centroid[iface*dim+d] = fg->centroid[d];
      normal[iface*dim+d]   = fg->normal[d];
    }
    vol[iface*2+0] = cgL->volume;
    vol[iface*2+1] = cgR->volume;
    ++iface;
  }
  if (computeGradients) {
    ierr = VecRestoreArrayRead(locGrad,&lgrad);CHKERRQ(ierr);
    ierr = DMRestoreLocalVector(dmplexts->dmGrad, &locGrad);CHKERRQ(ierr);
  }
  ierr = VecRestoreArrayRead(locX, &x);CHKERRQ(ierr);
  ierr = VecRestoreArrayRead(faceGeometry, &facegeom);CHKERRQ(ierr);
  ierr = VecRestoreArrayRead(cellGeometry, &cellgeom);CHKERRQ(ierr);
  fgeom.v0  = centroid;
  fgeom.n   = normal;
  cgeom.vol = vol;
  /* Riemann solve */
  ierr = PetscFVIntegrateRHSFunction(fvm, numFaces, Nf, &fvm, 0, fgeom, cgeom, uL, uR, riemann, fluxL, fluxR, dmplexts->rhsfunctionlocalctx);CHKERRQ(ierr);
  /* Insert fluxes */
  ierr = VecGetArray(F, &f);CHKERRQ(ierr);
  for (face = fStart, iface = 0; face < fEnd; ++face) {
    const PetscInt *cells;
    PetscScalar    *fL, *fR;
    PetscInt        ghost, d;

    ierr = DMLabelGetValue(ghostLabel, face, &ghost);CHKERRQ(ierr);
    if (ghost >= 0) continue;
    ierr = DMPlexGetSupport(dm, face, &cells);CHKERRQ(ierr);
    ierr = DMPlexPointGlobalRef(dm, cells[0], f, &fL);CHKERRQ(ierr);
    ierr = DMPlexPointGlobalRef(dm, cells[1], f, &fR);CHKERRQ(ierr);
    for (d = 0; d < pdim; ++d) {
      if (fL) fL[d] -= fluxL[iface*pdim+d];
      if (fR) fR[d] += fluxR[iface*pdim+d];
    }
    ++iface;
  }
  ierr = VecRestoreArray(F, &f);CHKERRQ(ierr);
  ierr = PetscFree7(centroid,normal,vol,uL,uR,fluxL,fluxR);CHKERRQ(ierr);
  ierr = DMRestoreLocalVector(dm, &locX);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
Esempio n. 6
0
File: dmi.c Progetto: plguhur/petsc
/* This assumes that the DM has been cloned prior to the call */
PetscErrorCode DMCreateSubDM_Section_Private(DM dm, PetscInt numFields, PetscInt fields[], IS *is, DM *subdm)
{
  PetscSection   section, sectionGlobal;
  PetscInt      *subIndices;
  PetscInt       subSize = 0, subOff = 0, nF, f, pStart, pEnd, p;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  if (!numFields) PetscFunctionReturn(0);
  ierr = DMGetDefaultSection(dm, &section);CHKERRQ(ierr);
  ierr = DMGetDefaultGlobalSection(dm, &sectionGlobal);CHKERRQ(ierr);
  if (!section) SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Must set default section for DM before splitting fields");
  if (!sectionGlobal) SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Must set default global section for DM before splitting fields");
  ierr = PetscSectionGetNumFields(section, &nF);CHKERRQ(ierr);
  if (numFields > nF) SETERRQ2(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Number of requested fields %d greater than number of DM fields %d", numFields, nF);
  if (is) {
    ierr = PetscSectionGetChart(sectionGlobal, &pStart, &pEnd);CHKERRQ(ierr);
    for (p = pStart; p < pEnd; ++p) {
      PetscInt gdof;

      ierr = PetscSectionGetDof(sectionGlobal, p, &gdof);CHKERRQ(ierr);
      if (gdof > 0) {
        for (f = 0; f < numFields; ++f) {
          PetscInt fdof, fcdof;

          ierr     = PetscSectionGetFieldDof(section, p, fields[f], &fdof);CHKERRQ(ierr);
          ierr     = PetscSectionGetFieldConstraintDof(section, p, fields[f], &fcdof);CHKERRQ(ierr);
          subSize += fdof-fcdof;
        }
      }
    }
    ierr = PetscMalloc1(subSize, &subIndices);CHKERRQ(ierr);
    for (p = pStart; p < pEnd; ++p) {
      PetscInt gdof, goff;

      ierr = PetscSectionGetDof(sectionGlobal, p, &gdof);CHKERRQ(ierr);
      if (gdof > 0) {
        ierr = PetscSectionGetOffset(sectionGlobal, p, &goff);CHKERRQ(ierr);
        for (f = 0; f < numFields; ++f) {
          PetscInt fdof, fcdof, fc, f2, poff = 0;

          /* Can get rid of this loop by storing field information in the global section */
          for (f2 = 0; f2 < fields[f]; ++f2) {
            ierr  = PetscSectionGetFieldDof(section, p, f2, &fdof);CHKERRQ(ierr);
            ierr  = PetscSectionGetFieldConstraintDof(section, p, f2, &fcdof);CHKERRQ(ierr);
            poff += fdof-fcdof;
          }
          ierr = PetscSectionGetFieldDof(section, p, fields[f], &fdof);CHKERRQ(ierr);
          ierr = PetscSectionGetFieldConstraintDof(section, p, fields[f], &fcdof);CHKERRQ(ierr);
          for (fc = 0; fc < fdof-fcdof; ++fc, ++subOff) {
            subIndices[subOff] = goff+poff+fc;
          }
        }
      }
    }
    ierr = ISCreateGeneral(PetscObjectComm((PetscObject)dm), subSize, subIndices, PETSC_OWN_POINTER, is);CHKERRQ(ierr);
  }
  if (subdm) {
    PetscSection subsection;
    PetscBool    haveNull = PETSC_FALSE;
    PetscInt     f, nf = 0;

    ierr = PetscSectionCreateSubsection(section, numFields, fields, &subsection);CHKERRQ(ierr);
    ierr = DMSetDefaultSection(*subdm, subsection);CHKERRQ(ierr);
    ierr = PetscSectionDestroy(&subsection);CHKERRQ(ierr);
    for (f = 0; f < numFields; ++f) {
      (*subdm)->nullspaceConstructors[f] = dm->nullspaceConstructors[fields[f]];
      if ((*subdm)->nullspaceConstructors[f]) {
        haveNull = PETSC_TRUE;
        nf       = f;
      }
    }
    if (haveNull && is) {
      MatNullSpace nullSpace;

      ierr = (*(*subdm)->nullspaceConstructors[nf])(*subdm, nf, &nullSpace);CHKERRQ(ierr);
      ierr = PetscObjectCompose((PetscObject) *is, "nullspace", (PetscObject) nullSpace);CHKERRQ(ierr);
      ierr = MatNullSpaceDestroy(&nullSpace);CHKERRQ(ierr);
    }
    if (dm->prob) {
      PetscInt Nf;

      ierr = PetscDSGetNumFields(dm->prob, &Nf);CHKERRQ(ierr);
      if (nF != Nf) SETERRQ2(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "The number of DM fields %d does not match the number of Section fields %d", Nf, nF);
      ierr = DMSetNumFields(*subdm, numFields);CHKERRQ(ierr);
      for (f = 0; f < numFields; ++f) {
        PetscObject disc;

        ierr = DMGetField(dm, fields[f], &disc);CHKERRQ(ierr);
        ierr = DMSetField(*subdm, f, disc);CHKERRQ(ierr);
      }
      if (numFields == 1 && is) {
        PetscObject disc, space, pmat;

        ierr = DMGetField(*subdm, 0, &disc);CHKERRQ(ierr);
        ierr = PetscObjectQuery(disc, "nullspace", &space);CHKERRQ(ierr);
        if (space) {ierr = PetscObjectCompose((PetscObject) *is, "nullspace", space);CHKERRQ(ierr);}
        ierr = PetscObjectQuery(disc, "nearnullspace", &space);CHKERRQ(ierr);
        if (space) {ierr = PetscObjectCompose((PetscObject) *is, "nearnullspace", space);CHKERRQ(ierr);}
        ierr = PetscObjectQuery(disc, "pmat", &pmat);CHKERRQ(ierr);
        if (pmat) {ierr = PetscObjectCompose((PetscObject) *is, "pmat", pmat);CHKERRQ(ierr);}
      }
    }
  }
#if 0
  /* We need a way to filter the original SF for given fields:
       - Keeping the original section around it too much I think
       - We could keep the distributed section, and subset it
   */
  if (dm->sfNatural) {
    PetscSF sfNatural;

    ierr = PetscSectionCreateSubsection(dm->originalSection, numFields, fields, &(*subdm)->originalSection);CHKERRQ(ierr);
    ierr = DMPlexCreateGlobalToNaturalPetscSF(*subdm, &sfNatural);CHKERRQ(ierr);
    ierr = DMPlexSetGlobalToNaturalPetscSF(*subdm, sfNatural);CHKERRQ(ierr);
  }
#endif
  PetscFunctionReturn(0);
}
Esempio n. 7
0
/*@
  PetscConvEstGetConvRate - Returns an estimate of the convergence rate for the discretization

  Not collective

  Input Parameter:
. ce   - The PetscConvEst object

  Output Parameter:
. alpha - The convergence rate for each field

  Note: The convergence rate alpha is defined by
$ || u_h - u_exact || < C h^alpha
where u_h is the discrete solution, and h is a measure of the discretization size.

We solve a series of problems on refined meshes, calculate an error based upon the exact solution in the DS,
and then fit the result to our model above using linear regression.

  Options database keys:
. -snes_convergence_estimate : Execute convergence estimation and print out the rate

  Level: intermediate

.keywords: PetscConvEst, convergence
.seealso: PetscConvEstSetSolver(), PetscConvEstCreate(), PetscConvEstGetConvRate()
@*/
PetscErrorCode PetscConvEstGetConvRate(PetscConvEst ce, PetscReal alpha[])
{
  DM            *dm;
  PetscObject    disc;
  MPI_Comm       comm;
  const char    *uname, *dmname;
  void          *ctx;
  Vec            u;
  PetscReal      t = 0.0, *x, *y, slope, intercept;
  PetscInt      *dof, dim, Nr = ce->Nr, r, f, oldlevel, oldnlev;
  PetscLogEvent  event;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectGetComm((PetscObject) ce, &comm);CHKERRQ(ierr);
  ierr = DMGetDimension(ce->idm, &dim);CHKERRQ(ierr);
  ierr = DMGetApplicationContext(ce->idm, &ctx);CHKERRQ(ierr);
  ierr = DMPlexSetRefinementUniform(ce->idm, PETSC_TRUE);CHKERRQ(ierr);
  ierr = DMGetRefineLevel(ce->idm, &oldlevel);CHKERRQ(ierr);
  ierr = PetscMalloc2((Nr+1), &dm, (Nr+1)*ce->Nf, &dof);CHKERRQ(ierr);
  dm[0]  = ce->idm;
  for (f = 0; f < ce->Nf; ++f) alpha[f] = 0.0;
  /* Loop over meshes */
  ierr = PetscLogEventRegister("ConvEst Error", PETSC_OBJECT_CLASSID, &event);CHKERRQ(ierr);
  for (r = 0; r <= Nr; ++r) {
    PetscLogStage stage;
    char          stageName[PETSC_MAX_PATH_LEN];

    ierr = PetscSNPrintf(stageName, PETSC_MAX_PATH_LEN-1, "ConvEst Refinement Level %D", r);CHKERRQ(ierr);
    ierr = PetscLogStageRegister(stageName, &stage);CHKERRQ(ierr);
    ierr = PetscLogStagePush(stage);CHKERRQ(ierr);
    if (r > 0) {
      ierr = DMRefine(dm[r-1], MPI_COMM_NULL, &dm[r]);CHKERRQ(ierr);
      ierr = DMSetCoarseDM(dm[r], dm[r-1]);CHKERRQ(ierr);
      ierr = DMCopyDisc(ce->idm, dm[r]);CHKERRQ(ierr);
      ierr = DMCopyTransform(ce->idm, dm[r]);CHKERRQ(ierr);
      ierr = PetscObjectGetName((PetscObject) dm[r-1], &dmname);CHKERRQ(ierr);
      ierr = PetscObjectSetName((PetscObject) dm[r], dmname);CHKERRQ(ierr);
      for (f = 0; f <= ce->Nf; ++f) {
        PetscErrorCode (*nspconstr)(DM, PetscInt, MatNullSpace *);
        ierr = DMGetNullSpaceConstructor(dm[r-1], f, &nspconstr);CHKERRQ(ierr);
        ierr = DMSetNullSpaceConstructor(dm[r],   f,  nspconstr);CHKERRQ(ierr);
      }
    }
    ierr = DMViewFromOptions(dm[r], NULL, "-conv_dm_view");CHKERRQ(ierr);
    /* Create solution */
    ierr = DMCreateGlobalVector(dm[r], &u);CHKERRQ(ierr);
    ierr = DMGetField(dm[r], 0, NULL, &disc);CHKERRQ(ierr);
    ierr = PetscObjectGetName(disc, &uname);CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject) u, uname);CHKERRQ(ierr);
    /* Setup solver */
    ierr = SNESReset(ce->snes);CHKERRQ(ierr);
    ierr = SNESSetDM(ce->snes, dm[r]);CHKERRQ(ierr);
    ierr = DMPlexSetSNESLocalFEM(dm[r], ctx, ctx, ctx);CHKERRQ(ierr);
    ierr = SNESSetFromOptions(ce->snes);CHKERRQ(ierr);
    /* Create initial guess */
    ierr = DMProjectFunction(dm[r], t, ce->initGuess, ce->ctxs, INSERT_VALUES, u);CHKERRQ(ierr);
    ierr = SNESSolve(ce->snes, NULL, u);CHKERRQ(ierr);
    ierr = PetscLogEventBegin(event, ce, 0, 0, 0);CHKERRQ(ierr);
    ierr = DMComputeL2FieldDiff(dm[r], t, ce->exactSol, ce->ctxs, u, &ce->errors[r*ce->Nf]);CHKERRQ(ierr);
    ierr = PetscLogEventEnd(event, ce, 0, 0, 0);CHKERRQ(ierr);
    for (f = 0; f < ce->Nf; ++f) {
      PetscSection s, fs;
      PetscInt     lsize;

      /* Could use DMGetOutputDM() to add in Dirichlet dofs */
      ierr = DMGetSection(dm[r], &s);CHKERRQ(ierr);
      ierr = PetscSectionGetField(s, f, &fs);CHKERRQ(ierr);
      ierr = PetscSectionGetConstrainedStorageSize(fs, &lsize);CHKERRQ(ierr);
      ierr = MPI_Allreduce(&lsize, &dof[r*ce->Nf+f], 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject) ce->snes));CHKERRQ(ierr);
      ierr = PetscLogEventSetDof(event, f, dof[r*ce->Nf+f]);CHKERRQ(ierr);
      ierr = PetscLogEventSetError(event, f, ce->errors[r*ce->Nf+f]);CHKERRQ(ierr);
    }
    /* Monitor */
    if (ce->monitor) {
      PetscReal *errors = &ce->errors[r*ce->Nf];

      ierr = PetscPrintf(comm, "L_2 Error: ");CHKERRQ(ierr);
      if (ce->Nf > 1) {ierr = PetscPrintf(comm, "[");CHKERRQ(ierr);}
      for (f = 0; f < ce->Nf; ++f) {
        if (f > 0) {ierr = PetscPrintf(comm, ", ");CHKERRQ(ierr);}
        if (errors[f] < 1.0e-11) {ierr = PetscPrintf(comm, "< 1e-11");CHKERRQ(ierr);}
        else                     {ierr = PetscPrintf(comm, "%g", (double)errors[f]);CHKERRQ(ierr);}
      }
      if (ce->Nf > 1) {ierr = PetscPrintf(comm, "]");CHKERRQ(ierr);}
      ierr = PetscPrintf(comm, "\n");CHKERRQ(ierr);
    }
    if (!r) {
      /* PCReset() does not wipe out the level structure */
      KSP ksp;
      PC  pc;

      ierr = SNESGetKSP(ce->snes, &ksp);CHKERRQ(ierr);
      ierr = KSPGetPC(ksp, &pc);CHKERRQ(ierr);
      ierr = PCMGGetLevels(pc, &oldnlev);CHKERRQ(ierr);
    }
    /* Cleanup */
    ierr = VecDestroy(&u);CHKERRQ(ierr);
    ierr = PetscLogStagePop();CHKERRQ(ierr);
  }
  for (r = 1; r <= Nr; ++r) {
    ierr = DMDestroy(&dm[r]);CHKERRQ(ierr);
  }
  /* Fit convergence rate */
  ierr = PetscMalloc2(Nr+1, &x, Nr+1, &y);CHKERRQ(ierr);
  for (f = 0; f < ce->Nf; ++f) {
    for (r = 0; r <= Nr; ++r) {
      x[r] = PetscLog10Real(dof[r*ce->Nf+f]);
      y[r] = PetscLog10Real(ce->errors[r*ce->Nf+f]);
    }
    ierr = PetscLinearRegression(Nr+1, x, y, &slope, &intercept);CHKERRQ(ierr);
    /* Since h^{-dim} = N, lg err = s lg N + b = -s dim lg h + b */
    alpha[f] = -slope * dim;
  }
  ierr = PetscFree2(x, y);CHKERRQ(ierr);
  ierr = PetscFree2(dm, dof);CHKERRQ(ierr);
  /* Restore solver */
  ierr = SNESReset(ce->snes);CHKERRQ(ierr);
  {
    /* PCReset() does not wipe out the level structure */
    KSP ksp;
    PC  pc;

    ierr = SNESGetKSP(ce->snes, &ksp);CHKERRQ(ierr);
    ierr = KSPGetPC(ksp, &pc);CHKERRQ(ierr);
    ierr = PCMGSetLevels(pc, oldnlev, NULL);CHKERRQ(ierr);
    ierr = DMSetRefineLevel(ce->idm, oldlevel);CHKERRQ(ierr); /* The damn DMCoarsen() calls in PCMG can reset this */
  }
  ierr = SNESSetDM(ce->snes, ce->idm);CHKERRQ(ierr);
  ierr = DMPlexSetSNESLocalFEM(ce->idm, ctx, ctx, ctx);CHKERRQ(ierr);
  ierr = SNESSetFromOptions(ce->snes);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}