impls/plex/plexglvis.c

#include <petsc/private/glvisviewerimpl.h>
#include <petsc/private/petscimpl.h>
#include <petsc/private/dmpleximpl.h>
#include <petscbt.h>
#include <petscdmplex.h>
#include <petscsf.h>
#include <petscds.h>

typedef struct {
  PetscInt   nf;
  VecScatter *scctx;
} GLVisViewerCtx;

static PetscErrorCode DestroyGLVisViewerCtx_Private(void *vctx)
{
  GLVisViewerCtx *ctx = (GLVisViewerCtx*)vctx;
  PetscInt       i;

  PetscFunctionBegin;
  for (i=0;i<ctx->nf;i++) {
    PetscCall(VecScatterDestroy(&ctx->scctx[i]));
  }
  PetscCall(PetscFree(ctx->scctx));
  PetscCall(PetscFree(vctx));
  PetscFunctionReturn(0);
}

static PetscErrorCode DMPlexSampleGLVisFields_Private(PetscObject oX, PetscInt nf, PetscObject oXfield[], void *vctx)
{
  GLVisViewerCtx *ctx = (GLVisViewerCtx*)vctx;
  PetscInt       f;

  PetscFunctionBegin;
  for (f=0;f<nf;f++) {
    PetscCall(VecScatterBegin(ctx->scctx[f],(Vec)oX,(Vec)oXfield[f],INSERT_VALUES,SCATTER_FORWARD));
    PetscCall(VecScatterEnd(ctx->scctx[f],(Vec)oX,(Vec)oXfield[f],INSERT_VALUES,SCATTER_FORWARD));
  }
  PetscFunctionReturn(0);
}

/* for FEM, it works for H1 fields only and extracts dofs at cell vertices, discarding any other dof */
PetscErrorCode DMSetUpGLVisViewer_Plex(PetscObject odm, PetscViewer viewer)
{
  DM             dm = (DM)odm;
  Vec            xlocal,xfield,*Ufield;
  PetscDS        ds;
  IS             globalNum,isfield;
  PetscBT        vown;
  char           **fieldname = NULL,**fec_type = NULL;
  const PetscInt *gNum;
  PetscInt       *nlocal,*bs,*idxs,*dims;
  PetscInt       f,maxfields,nfields,c,totc,totdofs,Nv,cum,i;
  PetscInt       dim,cStart,cEnd,vStart,vEnd;
  GLVisViewerCtx *ctx;
  PetscSection   s;

  PetscFunctionBegin;
  PetscCall(DMGetDimension(dm,&dim));
  PetscCall(DMPlexGetDepthStratum(dm,0,&vStart,&vEnd));
  PetscCall(DMPlexGetHeightStratum(dm,0,&cStart,&cEnd));
  PetscCall(PetscObjectQuery((PetscObject)dm,"_glvis_plex_gnum",(PetscObject*)&globalNum));
  if (!globalNum) {
    PetscCall(DMPlexCreateCellNumbering_Internal(dm,PETSC_TRUE,&globalNum));
    PetscCall(PetscObjectCompose((PetscObject)dm,"_glvis_plex_gnum",(PetscObject)globalNum));
    PetscCall(PetscObjectDereference((PetscObject)globalNum));
  }
  PetscCall(ISGetIndices(globalNum,&gNum));
  PetscCall(PetscBTCreate(vEnd-vStart,&vown));
  for (c = cStart, totc = 0; c < cEnd; c++) {
    if (gNum[c-cStart] >= 0) {
      PetscInt i,numPoints,*points = NULL;

      totc++;
      PetscCall(DMPlexGetTransitiveClosure(dm,c,PETSC_TRUE,&numPoints,&points));
      for (i=0;i<numPoints*2;i+= 2) {
        if ((points[i] >= vStart) && (points[i] < vEnd)) {
          PetscCall(PetscBTSet(vown,points[i]-vStart));
        }
      }
      PetscCall(DMPlexRestoreTransitiveClosure(dm,c,PETSC_TRUE,&numPoints,&points));
    }
  }
  for (f=0,Nv=0;f<vEnd-vStart;f++) if (PetscLikely(PetscBTLookup(vown,f))) Nv++;

  PetscCall(DMCreateLocalVector(dm,&xlocal));
  PetscCall(VecGetLocalSize(xlocal,&totdofs));
  PetscCall(DMGetLocalSection(dm,&s));
  PetscCall(PetscSectionGetNumFields(s,&nfields));
  for (f=0,maxfields=0;f<nfields;f++) {
    PetscInt bs;

    PetscCall(PetscSectionGetFieldComponents(s,f,&bs));
    maxfields += bs;
  }
  PetscCall(PetscCalloc7(maxfields,&fieldname,maxfields,&nlocal,maxfields,&bs,maxfields,&dims,maxfields,&fec_type,totdofs,&idxs,maxfields,&Ufield));
  PetscCall(PetscNew(&ctx));
  PetscCall(PetscCalloc1(maxfields,&ctx->scctx));
  PetscCall(DMGetDS(dm,&ds));
  if (ds) {
    for (f=0;f<nfields;f++) {
      const char* fname;
      char        name[256];
      PetscObject disc;
      size_t      len;

      PetscCall(PetscSectionGetFieldName(s,f,&fname));
      PetscCall(PetscStrlen(fname,&len));
      if (len) {
        PetscCall(PetscStrcpy(name,fname));
      } else {
        PetscCall(PetscSNPrintf(name,256,"Field%D",f));
      }
      PetscCall(PetscDSGetDiscretization(ds,f,&disc));
      if (disc) {
        PetscClassId id;
        PetscInt     Nc;
        char         fec[64];

        PetscCall(PetscObjectGetClassId(disc, &id));
        if (id == PETSCFE_CLASSID) {
          PetscFE            fem = (PetscFE)disc;
          PetscDualSpace     sp;
          PetscDualSpaceType spname;
          PetscInt           order;
          PetscBool          islag,continuous,H1 = PETSC_TRUE;

          PetscCall(PetscFEGetNumComponents(fem,&Nc));
          PetscCall(PetscFEGetDualSpace(fem,&sp));
          PetscCall(PetscDualSpaceGetType(sp,&spname));
          PetscCall(PetscStrcmp(spname,PETSCDUALSPACELAGRANGE,&islag));
          PetscCheck(islag,PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Unsupported dual space");
          PetscCall(PetscDualSpaceLagrangeGetContinuity(sp,&continuous));
          PetscCall(PetscDualSpaceGetOrder(sp,&order));
          if (continuous && order > 0) { /* no support for high-order viz, still have to figure out the numbering */
            PetscCall(PetscSNPrintf(fec,64,"FiniteElementCollection: H1_%DD_P1",dim));
          } else {
            PetscCheck(continuous || !order,PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Discontinuous space visualization currently unsupported for order %D",order);
            H1   = PETSC_FALSE;
            PetscCall(PetscSNPrintf(fec,64,"FiniteElementCollection: L2_%DD_P%D",dim,order));
          }
          PetscCall(PetscStrallocpy(name,&fieldname[ctx->nf]));
          bs[ctx->nf]   = Nc;
          dims[ctx->nf] = dim;
          if (H1) {
            nlocal[ctx->nf] = Nc * Nv;
            PetscCall(PetscStrallocpy(fec,&fec_type[ctx->nf]));
            PetscCall(VecCreateSeq(PETSC_COMM_SELF,Nv*Nc,&xfield));
            for (i=0,cum=0;i<vEnd-vStart;i++) {
              PetscInt j,off;

              if (PetscUnlikely(!PetscBTLookup(vown,i))) continue;
              PetscCall(PetscSectionGetFieldOffset(s,i+vStart,f,&off));
              for (j=0;j<Nc;j++) idxs[cum++] = off + j;
            }
            PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)xlocal),Nv*Nc,idxs,PETSC_USE_POINTER,&isfield));
          } else {
            nlocal[ctx->nf] = Nc * totc;
            PetscCall(PetscStrallocpy(fec,&fec_type[ctx->nf]));
            PetscCall(VecCreateSeq(PETSC_COMM_SELF,Nc*totc,&xfield));
            for (i=0,cum=0;i<cEnd-cStart;i++) {
              PetscInt j,off;

              if (PetscUnlikely(gNum[i] < 0)) continue;
              PetscCall(PetscSectionGetFieldOffset(s,i+cStart,f,&off));
              for (j=0;j<Nc;j++) idxs[cum++] = off + j;
            }
            PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)xlocal),totc*Nc,idxs,PETSC_USE_POINTER,&isfield));
          }
          PetscCall(VecScatterCreate(xlocal,isfield,xfield,NULL,&ctx->scctx[ctx->nf]));
          PetscCall(VecDestroy(&xfield));
          PetscCall(ISDestroy(&isfield));
          ctx->nf++;
        } else if (id == PETSCFV_CLASSID) {
          PetscInt c;

          PetscCall(PetscFVGetNumComponents((PetscFV)disc,&Nc));
          PetscCall(PetscSNPrintf(fec,64,"FiniteElementCollection: L2_%DD_P0",dim));
          for (c = 0; c < Nc; c++) {
            char comp[256];
            PetscCall(PetscSNPrintf(comp,256,"%s-Comp%D",name,c));
            PetscCall(PetscStrallocpy(comp,&fieldname[ctx->nf]));
            bs[ctx->nf] = 1; /* Does PetscFV support components with different block size? */
            nlocal[ctx->nf] = totc;
            dims[ctx->nf] = dim;
            PetscCall(PetscStrallocpy(fec,&fec_type[ctx->nf]));
            PetscCall(VecCreateSeq(PETSC_COMM_SELF,totc,&xfield));
            for (i=0,cum=0;i<cEnd-cStart;i++) {
              PetscInt off;

              if (PetscUnlikely(gNum[i])<0) continue;
              PetscCall(PetscSectionGetFieldOffset(s,i+cStart,f,&off));
              idxs[cum++] = off + c;
            }
            PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)xlocal),totc,idxs,PETSC_USE_POINTER,&isfield));
            PetscCall(VecScatterCreate(xlocal,isfield,xfield,NULL,&ctx->scctx[ctx->nf]));
            PetscCall(VecDestroy(&xfield));
            PetscCall(ISDestroy(&isfield));
            ctx->nf++;
          }
        } else SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_WRONG,"Unknown discretization type for field %D",f);
      } else SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Missing discretization for field %D",f);
    }
  } else SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Needs a DS attached to the DM");
  PetscCall(PetscBTDestroy(&vown));
  PetscCall(VecDestroy(&xlocal));
  PetscCall(ISRestoreIndices(globalNum,&gNum));

  /* create work vectors */
  for (f=0;f<ctx->nf;f++) {
    PetscCall(VecCreateMPI(PetscObjectComm((PetscObject)dm),nlocal[f],PETSC_DECIDE,&Ufield[f]));
    PetscCall(PetscObjectSetName((PetscObject)Ufield[f],fieldname[f]));
    PetscCall(VecSetBlockSize(Ufield[f],bs[f]));
    PetscCall(VecSetDM(Ufield[f],dm));
  }

  /* customize the viewer */
  PetscCall(PetscViewerGLVisSetFields(viewer,ctx->nf,(const char**)fec_type,dims,DMPlexSampleGLVisFields_Private,(PetscObject*)Ufield,ctx,DestroyGLVisViewerCtx_Private));
  for (f=0;f<ctx->nf;f++) {
    PetscCall(PetscFree(fieldname[f]));
    PetscCall(PetscFree(fec_type[f]));
    PetscCall(VecDestroy(&Ufield[f]));
  }
  PetscCall(PetscFree7(fieldname,nlocal,bs,dims,fec_type,idxs,Ufield));
  PetscFunctionReturn(0);
}

typedef enum {MFEM_POINT=0,MFEM_SEGMENT,MFEM_TRIANGLE,MFEM_SQUARE,MFEM_TETRAHEDRON,MFEM_CUBE,MFEM_PRISM,MFEM_UNDEF} MFEM_cid;

MFEM_cid mfem_table_cid[4][7]       = { {MFEM_POINT,MFEM_UNDEF,MFEM_UNDEF  ,MFEM_UNDEF   ,MFEM_UNDEF      ,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_UNDEF   ,MFEM_UNDEF      ,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_TRIANGLE,MFEM_SQUARE     ,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_UNDEF   ,MFEM_TETRAHEDRON,MFEM_PRISM,MFEM_CUBE } };

MFEM_cid mfem_table_cid_unint[4][9] = { {MFEM_POINT,MFEM_UNDEF,MFEM_UNDEF  ,MFEM_UNDEF   ,MFEM_UNDEF      ,MFEM_UNDEF,MFEM_PRISM,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_UNDEF   ,MFEM_UNDEF      ,MFEM_UNDEF,MFEM_PRISM,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_TRIANGLE,MFEM_SQUARE     ,MFEM_UNDEF,MFEM_PRISM,MFEM_UNDEF,MFEM_UNDEF},
                                        {MFEM_POINT,MFEM_UNDEF,MFEM_SEGMENT,MFEM_UNDEF   ,MFEM_TETRAHEDRON,MFEM_UNDEF,MFEM_PRISM,MFEM_UNDEF,MFEM_CUBE } };

static PetscErrorCode DMPlexGetPointMFEMCellID_Internal(DM dm, DMLabel label, PetscInt minl, PetscInt p, PetscInt *mid, PetscInt *cid)
{
  DMLabel        dlabel;
  PetscInt       depth,csize,pdepth,dim;

  PetscFunctionBegin;
  PetscCall(DMPlexGetDepthLabel(dm,&dlabel));
  PetscCall(DMLabelGetValue(dlabel,p,&pdepth));
  PetscCall(DMPlexGetConeSize(dm,p,&csize));
  PetscCall(DMPlexGetDepth(dm,&depth));
  PetscCall(DMGetDimension(dm,&dim));
  if (label) {
    PetscCall(DMLabelGetValue(label,p,mid));
    *mid = *mid - minl + 1; /* MFEM does not like negative markers */
  } else *mid = 1;
  if (depth >=0 && dim != depth) { /* not interpolated, it assumes cell-vertex mesh */
    PetscCheckFalse(dim < 0 || dim > 3,PETSC_COMM_SELF,PETSC_ERR_SUP,"Dimension %D",dim);
    PetscCheck(csize <= 8,PETSC_COMM_SELF,PETSC_ERR_SUP,"Found cone size %D for point %D",csize,p);
    PetscCheck(depth == 1,PETSC_COMM_SELF,PETSC_ERR_SUP,"Found depth %D for point %D. You should interpolate the mesh first",depth,p);
    *cid = mfem_table_cid_unint[dim][csize];
  } else {
    PetscCheck(csize <= 6,PETSC_COMM_SELF,PETSC_ERR_SUP,"Cone size %D for point %D",csize,p);
    PetscCheckFalse(pdepth < 0 || pdepth > 3,PETSC_COMM_SELF,PETSC_ERR_SUP,"Depth %D for point %D",csize,p);
    *cid = mfem_table_cid[pdepth][csize];
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode DMPlexGetPointMFEMVertexIDs_Internal(DM dm, PetscInt p, PetscSection csec, PetscInt *nv, PetscInt vids[])
{
  PetscInt       dim,sdim,dof = 0,off = 0,i,q,vStart,vEnd,numPoints,*points = NULL;

  PetscFunctionBegin;
  PetscCall(DMPlexGetDepthStratum(dm,0,&vStart,&vEnd));
  PetscCall(DMGetDimension(dm,&dim));
  sdim = dim;
  if (csec) {
    PetscInt sStart,sEnd;

    PetscCall(DMGetCoordinateDim(dm,&sdim));
    PetscCall(PetscSectionGetChart(csec,&sStart,&sEnd));
    PetscCall(PetscSectionGetOffset(csec,vStart,&off));
    off  = off/sdim;
    if (p >= sStart && p < sEnd) {
      PetscCall(PetscSectionGetDof(csec,p,&dof));
    }
  }
  if (!dof) {
    PetscCall(DMPlexGetTransitiveClosure(dm,p,PETSC_TRUE,&numPoints,&points));
    for (i=0,q=0;i<numPoints*2;i+= 2)
      if ((points[i] >= vStart) && (points[i] < vEnd))
        vids[q++] = points[i]-vStart+off;
    PetscCall(DMPlexRestoreTransitiveClosure(dm,p,PETSC_TRUE,&numPoints,&points));
  } else {
    PetscCall(PetscSectionGetOffset(csec,p,&off));
    PetscCall(PetscSectionGetDof(csec,p,&dof));
    for (q=0;q<dof/sdim;q++) vids[q] = off/sdim + q;
  }
  *nv = q;
  PetscFunctionReturn(0);
}

static PetscErrorCode GLVisCreateFE(PetscFE femIn,char name[32],PetscFE *fem,IS *perm)
{
  DM              K;
  PetscSpace      P;
  PetscDualSpace  Q;
  PetscQuadrature q,fq;
  PetscInt        dim,deg,dof;
  DMPolytopeType  ptype;
  PetscBool       isSimplex,isTensor;
  PetscBool       continuity = PETSC_FALSE;
  PetscDTNodeType nodeType   = PETSCDTNODES_GAUSSJACOBI;
  PetscBool       endpoint   = PETSC_TRUE;
  MPI_Comm        comm;

  PetscFunctionBegin;
  PetscCall(PetscObjectGetComm((PetscObject)femIn, &comm));
  PetscCall(PetscFEGetBasisSpace(femIn,&P));
  PetscCall(PetscFEGetDualSpace(femIn,&Q));
  PetscCall(PetscDualSpaceGetDM(Q,&K));
  PetscCall(DMGetDimension(K,&dim));
  PetscCall(PetscSpaceGetDegree(P,&deg,NULL));
  PetscCall(PetscSpaceGetNumComponents(P,&dof));
  PetscCall(DMPlexGetCellType(K,0,&ptype));
  switch (ptype) {
  case DM_POLYTOPE_QUADRILATERAL:
  case DM_POLYTOPE_HEXAHEDRON:
    isSimplex = PETSC_FALSE; break;
  default:
    isSimplex = PETSC_TRUE; break;
  }
  isTensor = isSimplex ? PETSC_FALSE : PETSC_TRUE;
  if (isSimplex) deg = PetscMin(deg,3); /* Permutation not coded for degree higher than 3 */
  /* Create space */
  PetscCall(PetscSpaceCreate(comm,&P));
  PetscCall(PetscSpaceSetType(P,PETSCSPACEPOLYNOMIAL));
  PetscCall(PetscSpacePolynomialSetTensor(P,isTensor));
  PetscCall(PetscSpaceSetNumComponents(P,dof));
  PetscCall(PetscSpaceSetNumVariables(P,dim));
  PetscCall(PetscSpaceSetDegree(P,deg,PETSC_DETERMINE));
  PetscCall(PetscSpaceSetUp(P));
  /* Create dual space */
  PetscCall(PetscDualSpaceCreate(comm,&Q));
  PetscCall(PetscDualSpaceSetType(Q,PETSCDUALSPACELAGRANGE));
  PetscCall(PetscDualSpaceLagrangeSetTensor(Q,isTensor));
  PetscCall(PetscDualSpaceLagrangeSetContinuity(Q,continuity));
  PetscCall(PetscDualSpaceLagrangeSetNodeType(Q,nodeType,endpoint,0));
  PetscCall(PetscDualSpaceSetNumComponents(Q,dof));
  PetscCall(PetscDualSpaceSetOrder(Q,deg));
  PetscCall(DMPlexCreateReferenceCell(PETSC_COMM_SELF, DMPolytopeTypeSimpleShape(dim, isSimplex), &K));
  PetscCall(PetscDualSpaceSetDM(Q,K));
  PetscCall(DMDestroy(&K));
  PetscCall(PetscDualSpaceSetUp(Q));
  /* Create quadrature */
  if (isSimplex) {
    PetscCall(PetscDTStroudConicalQuadrature(dim,  1,deg+1,-1,+1,&q));
    PetscCall(PetscDTStroudConicalQuadrature(dim-1,1,deg+1,-1,+1,&fq));
  } else {
    PetscCall(PetscDTGaussTensorQuadrature(dim,  1,deg+1,-1,+1,&q));
    PetscCall(PetscDTGaussTensorQuadrature(dim-1,1,deg+1,-1,+1,&fq));
  }
  /* Create finite element */
  PetscCall(PetscFECreate(comm,fem));
  PetscCall(PetscSNPrintf(name,32,"L2_T1_%DD_P%D",dim,deg));
  PetscCall(PetscObjectSetName((PetscObject)*fem,name));
  PetscCall(PetscFESetType(*fem,PETSCFEBASIC));
  PetscCall(PetscFESetNumComponents(*fem,dof));
  PetscCall(PetscFESetBasisSpace(*fem,P));
  PetscCall(PetscFESetDualSpace(*fem,Q));
  PetscCall(PetscFESetQuadrature(*fem,q));
  PetscCall(PetscFESetFaceQuadrature(*fem,fq));
  PetscCall(PetscFESetUp(*fem));

  /* Both MFEM and PETSc are lexicographic, but PLEX stores the swapped cone */
  *perm = NULL;
  if (isSimplex && dim == 3) {
    PetscInt celldofs,*pidx;

    PetscCall(PetscDualSpaceGetDimension(Q,&celldofs));
    celldofs /= dof;
    PetscCall(PetscMalloc1(celldofs,&pidx));
    switch (celldofs) {
    case 4:
      pidx[0] = 2;
      pidx[1] = 0;
      pidx[2] = 1;
      pidx[3] = 3;
    break;
    case 10:
      pidx[0] = 5;
      pidx[1] = 3;
      pidx[2] = 0;
      pidx[3] = 4;
      pidx[4] = 1;
      pidx[5] = 2;
      pidx[6] = 8;
      pidx[7] = 6;
      pidx[8] = 7;
      pidx[9] = 9;
    break;
    case 20:
      pidx[ 0] = 9;
      pidx[ 1] = 7;
      pidx[ 2] = 4;
      pidx[ 3] = 0;
      pidx[ 4] = 8;
      pidx[ 5] = 5;
      pidx[ 6] = 1;
      pidx[ 7] = 6;
      pidx[ 8] = 2;
      pidx[ 9] = 3;
      pidx[10] = 15;
      pidx[11] = 13;
      pidx[12] = 10;
      pidx[13] = 14;
      pidx[14] = 11;
      pidx[15] = 12;
      pidx[16] = 18;
      pidx[17] = 16;
      pidx[18] = 17;
      pidx[19] = 19;
    break;
    default:
      SETERRQ(comm,PETSC_ERR_SUP,"Unhandled degree,dof pair %D,%D",deg,celldofs);
    break;
    }
    PetscCall(ISCreateBlock(PETSC_COMM_SELF,dof,celldofs,pidx,PETSC_OWN_POINTER,perm));
  }

  /* Cleanup */
  PetscCall(PetscSpaceDestroy(&P));
  PetscCall(PetscDualSpaceDestroy(&Q));
  PetscCall(PetscQuadratureDestroy(&q));
  PetscCall(PetscQuadratureDestroy(&fq));
  PetscFunctionReturn(0);
}

/*
   ASCII visualization/dump: full support for simplices and tensor product cells. It supports AMR
   Higher order meshes are also supported
*/
static PetscErrorCode DMPlexView_GLVis_ASCII(DM dm, PetscViewer viewer)
{
  DMLabel              label;
  PetscSection         coordSection,parentSection,hoSection = NULL;
  Vec                  coordinates,hovec;
  const PetscScalar    *array;
  PetscInt             bf,p,sdim,dim,depth,novl,minl;
  PetscInt             cStart,cEnd,vStart,vEnd,nvert;
  PetscMPIInt          size;
  PetscBool            localized,isascii;
  PetscBool            enable_mfem,enable_boundary,enable_ncmesh,view_ovl = PETSC_FALSE;
  PetscBT              pown,vown;
  PetscContainer       glvis_container;
  PetscBool            cellvertex = PETSC_FALSE, periodic, enabled = PETSC_TRUE;
  PetscBool            enable_emark,enable_bmark;
  const char           *fmt;
  char                 emark[64] = "",bmark[64] = "";

  PetscFunctionBegin;
  PetscValidHeaderSpecific(dm,DM_CLASSID,1);
  PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
  PetscCall(PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isascii));
  PetscCheck(isascii,PetscObjectComm((PetscObject)viewer),PETSC_ERR_SUP,"Viewer must be of type VIEWERASCII");
  PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)viewer),&size));
  PetscCheck(size <= 1,PetscObjectComm((PetscObject)viewer),PETSC_ERR_SUP,"Use single sequential viewers for parallel visualization");
  PetscCall(DMGetDimension(dm,&dim));
  PetscCall(DMPlexGetDepth(dm,&depth));

  /* get container: determines if a process visualizes is portion of the data or not */
  PetscCall(PetscObjectQuery((PetscObject)viewer,"_glvis_info_container",(PetscObject*)&glvis_container));
  PetscCheck(glvis_container,PetscObjectComm((PetscObject)dm),PETSC_ERR_PLIB,"Missing GLVis container");
  {
    PetscViewerGLVisInfo glvis_info;
    PetscCall(PetscContainerGetPointer(glvis_container,(void**)&glvis_info));
    enabled = glvis_info->enabled;
    fmt     = glvis_info->fmt;
  }

  /* Users can attach a coordinate vector to the DM in case they have a higher-order mesh */
  PetscCall(PetscObjectQuery((PetscObject)dm,"_glvis_mesh_coords",(PetscObject*)&hovec));
  PetscCall(PetscObjectReference((PetscObject)hovec));
  if (!hovec) {
    DM           cdm;
    PetscFE      disc;
    PetscClassId classid;

    PetscCall(DMGetCoordinateDM(dm,&cdm));
    PetscCall(DMGetField(cdm,0,NULL,(PetscObject*)&disc));
    PetscCall(PetscObjectGetClassId((PetscObject)disc,&classid));
    if (classid == PETSCFE_CLASSID) {
      DM      hocdm;
      PetscFE hodisc;
      Vec     vec;
      Mat     mat;
      char    name[32],fec_type[64];
      IS      perm = NULL;

      PetscCall(GLVisCreateFE(disc,name,&hodisc,&perm));
      PetscCall(DMClone(cdm,&hocdm));
      PetscCall(DMSetField(hocdm,0,NULL,(PetscObject)hodisc));
      PetscCall(PetscFEDestroy(&hodisc));
      PetscCall(DMCreateDS(hocdm));

      PetscCall(DMGetCoordinates(dm,&vec));
      PetscCall(DMCreateGlobalVector(hocdm,&hovec));
      PetscCall(DMCreateInterpolation(cdm,hocdm,&mat,NULL));
      PetscCall(MatInterpolate(mat,vec,hovec));
      PetscCall(MatDestroy(&mat));
      PetscCall(DMGetLocalSection(hocdm,&hoSection));
      PetscCall(PetscSectionSetClosurePermutation(hoSection, (PetscObject)hocdm, depth, perm));
      PetscCall(ISDestroy(&perm));
      PetscCall(DMDestroy(&hocdm));
      PetscCall(PetscSNPrintf(fec_type,sizeof(fec_type),"FiniteElementCollection: %s", name));
      PetscCall(PetscObjectSetName((PetscObject)hovec,fec_type));
    }
  }

  PetscCall(DMPlexGetHeightStratum(dm,0,&cStart,&cEnd));
  PetscCall(DMPlexGetGhostCellStratum(dm,&p,NULL));
  if (p >= 0) cEnd = p;
  PetscCall(DMPlexGetDepthStratum(dm,0,&vStart,&vEnd));
  PetscCall(DMGetPeriodicity(dm,&periodic,NULL,NULL,NULL));
  PetscCall(DMGetCoordinatesLocalized(dm,&localized));
  PetscCheckFalse(periodic && !localized && !hovec,PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Coordinates need to be localized");
  PetscCall(DMGetCoordinateSection(dm,&coordSection));
  PetscCall(DMGetCoordinateDim(dm,&sdim));
  PetscCall(DMGetCoordinatesLocal(dm,&coordinates));
  PetscCheck(coordinates || hovec,PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Missing local coordinates vector");

  /*
     a couple of sections of the mesh specification are disabled
       - boundary: the boundary is not needed for proper mesh visualization unless we want to visualize boundary attributes or we have high-order coordinates in 3D (topologically)
       - vertex_parents: used for non-conforming meshes only when we want to use MFEM as a discretization package
                         and be able to derefine the mesh (MFEM does not currently have to ability to read ncmeshes in parallel)
  */
  enable_boundary = PETSC_FALSE;
  enable_ncmesh   = PETSC_FALSE;
  enable_mfem     = PETSC_FALSE;
  enable_emark    = PETSC_FALSE;
  enable_bmark    = PETSC_FALSE;
  /* I'm tired of problems with negative values in the markers, disable them */
  PetscOptionsBegin(PetscObjectComm((PetscObject)dm),((PetscObject)dm)->prefix,"GLVis PetscViewer DMPlex Options","PetscViewer");
  PetscCall(PetscOptionsBool("-viewer_glvis_dm_plex_enable_boundary","Enable boundary section in mesh representation",NULL,enable_boundary,&enable_boundary,NULL));
  PetscCall(PetscOptionsBool("-viewer_glvis_dm_plex_enable_ncmesh","Enable vertex_parents section in mesh representation (allows derefinement)",NULL,enable_ncmesh,&enable_ncmesh,NULL));
  PetscCall(PetscOptionsBool("-viewer_glvis_dm_plex_enable_mfem","Dump a mesh that can be used with MFEM's FiniteElementSpaces",NULL,enable_mfem,&enable_mfem,NULL));
  PetscCall(PetscOptionsBool("-viewer_glvis_dm_plex_overlap","Include overlap region in local meshes",NULL,view_ovl,&view_ovl,NULL));
  PetscCall(PetscOptionsString("-viewer_glvis_dm_plex_emarker","String for the material id label",NULL,emark,emark,sizeof(emark),&enable_emark));
  PetscCall(PetscOptionsString("-viewer_glvis_dm_plex_bmarker","String for the boundary id label",NULL,bmark,bmark,sizeof(bmark),&enable_bmark));
  PetscOptionsEnd();
  if (enable_bmark) enable_boundary = PETSC_TRUE;

  PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)dm),&size));
  PetscCheckFalse(enable_ncmesh && size > 1,PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Not supported in parallel");
  PetscCheckFalse(enable_boundary && depth >= 0 && dim != depth,PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Mesh must be interpolated. "
                                                             "Alternatively, run with -viewer_glvis_dm_plex_enable_boundary 0");
  PetscCheckFalse(enable_ncmesh && depth >= 0 && dim != depth,PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Mesh must be interpolated. "
                                                           "Alternatively, run with -viewer_glvis_dm_plex_enable_ncmesh 0");
  if (depth >=0 && dim != depth) { /* not interpolated, it assumes cell-vertex mesh */
    PetscCheck(depth == 1,PETSC_COMM_SELF,PETSC_ERR_SUP,"Unsupported depth %D. You should interpolate the mesh first",depth);
    cellvertex = PETSC_TRUE;
  }

  /* Identify possible cells in the overlap */
  novl = 0;
  pown = NULL;
  if (size > 1) {
    IS             globalNum = NULL;
    const PetscInt *gNum;
    PetscBool      ovl  = PETSC_FALSE;

    PetscCall(PetscObjectQuery((PetscObject)dm,"_glvis_plex_gnum",(PetscObject*)&globalNum));
    if (!globalNum) {
      if (view_ovl) {
        PetscCall(ISCreateStride(PetscObjectComm((PetscObject)dm),cEnd-cStart,0,1,&globalNum));
      } else {
        PetscCall(DMPlexCreateCellNumbering_Internal(dm,PETSC_TRUE,&globalNum));
      }
      PetscCall(PetscObjectCompose((PetscObject)dm,"_glvis_plex_gnum",(PetscObject)globalNum));
      PetscCall(PetscObjectDereference((PetscObject)globalNum));
    }
    PetscCall(ISGetIndices(globalNum,&gNum));
    for (p=cStart; p<cEnd; p++) {
      if (gNum[p-cStart] < 0) {
        ovl = PETSC_TRUE;
        novl++;
      }
    }
    if (ovl) {
      /* it may happen that pown get not destroyed, if the user closes the window while this function is running.
         TODO: garbage collector? attach pown to dm?  */
      PetscCall(PetscBTCreate(cEnd-cStart,&pown));
      for (p=cStart; p<cEnd; p++) {
        if (gNum[p-cStart] < 0) continue;
        else {
          PetscCall(PetscBTSet(pown,p-cStart));
        }
      }
    }
    PetscCall(ISRestoreIndices(globalNum,&gNum));
  }

  /* vertex_parents (Non-conforming meshes) */
  parentSection  = NULL;
  if (enable_ncmesh) {
    PetscCall(DMPlexGetTree(dm,&parentSection,NULL,NULL,NULL,NULL));
    enable_ncmesh = (PetscBool)(enable_ncmesh && parentSection);
  }
  /* return if this process is disabled */
  if (!enabled) {
    PetscCall(PetscViewerASCIIPrintf(viewer,"MFEM mesh %s\n",enable_ncmesh ? "v1.1" : "v1.0"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"\ndimension\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",dim));
    PetscCall(PetscViewerASCIIPrintf(viewer,"\nelements\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",0));
    PetscCall(PetscViewerASCIIPrintf(viewer,"\nboundary\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",0));
    PetscCall(PetscViewerASCIIPrintf(viewer,"\nvertices\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",0));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",sdim));
    PetscCall(PetscBTDestroy(&pown));
    PetscCall(VecDestroy(&hovec));
    PetscFunctionReturn(0);
  }

  if (enable_mfem) {
    if (periodic && !hovec) { /* we need to generate a vector of L2 coordinates, as this is how MFEM handles periodic meshes */
      PetscInt    vpc = 0;
      char        fec[64];
      PetscInt    vids[8] = {0,1,2,3,4,5,6,7};
      PetscInt    hexv[8] = {0,1,3,2,4,5,7,6}, tetv[4] = {0,1,2,3};
      PetscInt    quadv[8] = {0,1,3,2}, triv[3] = {0,1,2};
      PetscInt    *dof = NULL;
      PetscScalar *array,*ptr;

      PetscCall(PetscSNPrintf(fec,sizeof(fec),"FiniteElementCollection: L2_T1_%DD_P1",dim));
      if (cEnd-cStart) {
        PetscInt fpc;

        PetscCall(DMPlexGetConeSize(dm,cStart,&fpc));
        switch(dim) {
          case 1:
            vpc = 2;
            dof = hexv;
            break;
          case 2:
            switch (fpc) {
              case 3:
                vpc = 3;
                dof = triv;
                break;
              case 4:
                vpc = 4;
                dof = quadv;
                break;
              default:
                SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Unhandled case: faces per cell %D",fpc);
            }
            break;
          case 3:
            switch (fpc) {
              case 4: /* TODO: still need to understand L2 ordering for tets */
                vpc = 4;
                dof = tetv;
                SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Unhandled tethraedral case");
              case 6:
                PetscCheck(!cellvertex,PETSC_COMM_SELF,PETSC_ERR_SUP,"Unhandled case: vertices per cell %D",fpc);
                vpc = 8;
                dof = hexv;
                break;
              case 8:
                PetscCheck(cellvertex,PETSC_COMM_SELF,PETSC_ERR_SUP,"Unhandled case: faces per cell %D",fpc);
                vpc = 8;
                dof = hexv;
                break;
              default:
                SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Unhandled case: faces per cell %D",fpc);
            }
            break;
          default:
            SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_SUP,"Unhandled dim");
        }
        PetscCall(DMPlexReorderCell(dm,cStart,vids));
      }
      PetscCheck(dof,PetscObjectComm((PetscObject)dm),PETSC_ERR_PLIB,"Missing dofs");
      PetscCall(VecCreateSeq(PETSC_COMM_SELF,(cEnd-cStart-novl)*vpc*sdim,&hovec));
      PetscCall(PetscObjectSetName((PetscObject)hovec,fec));
      PetscCall(VecGetArray(hovec,&array));
      ptr  = array;
      for (p=cStart;p<cEnd;p++) {
        PetscInt    csize,v,d;
        PetscScalar *vals = NULL;

        if (PetscUnlikely(pown && !PetscBTLookup(pown,p-cStart))) continue;
        PetscCall(DMPlexVecGetClosure(dm,coordSection,coordinates,p,&csize,&vals));
        PetscCheckFalse(csize != vpc*sdim && csize != vpc*sdim*2,PETSC_COMM_SELF,PETSC_ERR_SUP,"Unsupported closure size %D (vpc %D, sdim %D)",csize,vpc,sdim);
        for (v=0;v<vpc;v++) {
          for (d=0;d<sdim;d++) {
            ptr[sdim*dof[v]+d] = vals[sdim*vids[v]+d];
          }
        }
        ptr += vpc*sdim;
        PetscCall(DMPlexVecRestoreClosure(dm,coordSection,coordinates,p,&csize,&vals));
      }
      PetscCall(VecRestoreArray(hovec,&array));
    }
  }
  /* if we have high-order coordinates in 3D, we need to specify the boundary */
  if (hovec && dim == 3) enable_boundary = PETSC_TRUE;

  /* header */
  PetscCall(PetscViewerASCIIPrintf(viewer,"MFEM mesh %s\n",enable_ncmesh ? "v1.1" : "v1.0"));

  /* topological dimension */
  PetscCall(PetscViewerASCIIPrintf(viewer,"\ndimension\n"));
  PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",dim));

  /* elements */
  minl = 1;
  label = NULL;
  if (enable_emark) {
    PetscInt lminl = PETSC_MAX_INT;

    PetscCall(DMGetLabel(dm,emark,&label));
    if (label) {
      IS       vals;
      PetscInt ldef;

      PetscCall(DMLabelGetDefaultValue(label,&ldef));
      PetscCall(DMLabelGetValueIS(label,&vals));
      PetscCall(ISGetMinMax(vals,&lminl,NULL));
      PetscCall(ISDestroy(&vals));
      lminl = PetscMin(ldef,lminl);
    }
    PetscCall(MPIU_Allreduce(&lminl,&minl,1,MPIU_INT,MPI_MIN,PetscObjectComm((PetscObject)dm)));
    if (minl == PETSC_MAX_INT) minl = 1;
  }
  PetscCall(PetscViewerASCIIPrintf(viewer,"\nelements\n"));
  PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",cEnd-cStart-novl));
  for (p=cStart;p<cEnd;p++) {
    PetscInt       vids[8];
    PetscInt       i,nv = 0,cid = -1,mid = 1;

    if (PetscUnlikely(pown && !PetscBTLookup(pown,p-cStart))) continue;
    PetscCall(DMPlexGetPointMFEMCellID_Internal(dm,label,minl,p,&mid,&cid));
    PetscCall(DMPlexGetPointMFEMVertexIDs_Internal(dm,p,(localized && !hovec) ? coordSection : NULL,&nv,vids));
    PetscCall(DMPlexReorderCell(dm,p,vids));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D %D",mid,cid));
    for (i=0;i<nv;i++) {
      PetscCall(PetscViewerASCIIPrintf(viewer," %D",vids[i]));
    }
    PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
  }

  /* boundary */
  PetscCall(PetscViewerASCIIPrintf(viewer,"\nboundary\n"));
  if (!enable_boundary) {
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",0));
  } else {
    DMLabel  perLabel;
    PetscBT  bfaces;
    PetscInt fStart,fEnd,*fcells;

    PetscCall(DMPlexGetHeightStratum(dm,1,&fStart,&fEnd));
    PetscCall(PetscBTCreate(fEnd-fStart,&bfaces));
    PetscCall(DMPlexGetMaxSizes(dm,NULL,&p));
    PetscCall(PetscMalloc1(p,&fcells));
    PetscCall(DMGetLabel(dm,"glvis_periodic_cut",&perLabel));
    if (!perLabel && periodic) { /* this periodic cut can be moved up to DMPlex setup */
      PetscCall(DMCreateLabel(dm,"glvis_periodic_cut"));
      PetscCall(DMGetLabel(dm,"glvis_periodic_cut",&perLabel));
      PetscCall(DMLabelSetDefaultValue(perLabel,1));
      for (p=cStart;p<cEnd;p++) {
        DMPolytopeType cellType;
        PetscInt       dof;

        PetscCall(DMPlexGetCellType(dm,p,&cellType));
        PetscCall(PetscSectionGetDof(coordSection,p,&dof));
        if (dof) {
          PetscInt    uvpc, v,csize,cellClosureSize,*cellClosure = NULL,*vidxs = NULL;
          PetscScalar *vals = NULL;

          uvpc = DMPolytopeTypeGetNumVertices(cellType);
          PetscCheck(dof%sdim == 0,PETSC_COMM_SELF,PETSC_ERR_USER,"Incompatible number of cell dofs %D and space dimension %D",dof,sdim);
          PetscCall(DMPlexVecGetClosure(dm,coordSection,coordinates,p,&csize,&vals));
          PetscCall(DMPlexGetTransitiveClosure(dm,p,PETSC_TRUE,&cellClosureSize,&cellClosure));
          for (v=0;v<cellClosureSize;v++)
            if (cellClosure[2*v] >= vStart && cellClosure[2*v] < vEnd) {
              vidxs = cellClosure + 2*v;
              break;
            }
          PetscCheck(vidxs,PETSC_COMM_SELF,PETSC_ERR_PLIB,"Missing vertices");
          for (v=0;v<uvpc;v++) {
            PetscInt s;

            for (s=0;s<sdim;s++) {
              if (PetscAbsScalar(vals[v*sdim+s]-vals[v*sdim+s+uvpc*sdim])>PETSC_MACHINE_EPSILON) {
                PetscCall(DMLabelSetValue(perLabel,vidxs[2*v],2));
              }
            }
          }
          PetscCall(DMPlexRestoreTransitiveClosure(dm,p,PETSC_TRUE,&cellClosureSize,&cellClosure));
          PetscCall(DMPlexVecRestoreClosure(dm,coordSection,coordinates,p,&csize,&vals));
        }
      }
      if (dim > 1) {
        PetscInt eEnd,eStart;

        PetscCall(DMPlexGetDepthStratum(dm,1,&eStart,&eEnd));
        for (p=eStart;p<eEnd;p++) {
          const PetscInt *cone;
          PetscInt       coneSize,i;
          PetscBool      ispe = PETSC_TRUE;

          PetscCall(DMPlexGetCone(dm,p,&cone));
          PetscCall(DMPlexGetConeSize(dm,p,&coneSize));
          for (i=0;i<coneSize;i++) {
            PetscInt v;

            PetscCall(DMLabelGetValue(perLabel,cone[i],&v));
            ispe = (PetscBool)(ispe && (v==2));
          }
          if (ispe && coneSize) {
            PetscInt       ch, numChildren;
            const PetscInt *children;

            PetscCall(DMLabelSetValue(perLabel,p,2));
            PetscCall(DMPlexGetTreeChildren(dm,p,&numChildren,&children));
            for (ch = 0; ch < numChildren; ch++) {
              PetscCall(DMLabelSetValue(perLabel,children[ch],2));
            }
          }
        }
        if (dim > 2) {
          for (p=fStart;p<fEnd;p++) {
            const PetscInt *cone;
            PetscInt       coneSize,i;
            PetscBool      ispe = PETSC_TRUE;

            PetscCall(DMPlexGetCone(dm,p,&cone));
            PetscCall(DMPlexGetConeSize(dm,p,&coneSize));
            for (i=0;i<coneSize;i++) {
              PetscInt v;

              PetscCall(DMLabelGetValue(perLabel,cone[i],&v));
              ispe = (PetscBool)(ispe && (v==2));
            }
            if (ispe && coneSize) {
              PetscInt       ch, numChildren;
              const PetscInt *children;

              PetscCall(DMLabelSetValue(perLabel,p,2));
              PetscCall(DMPlexGetTreeChildren(dm,p,&numChildren,&children));
              for (ch = 0; ch < numChildren; ch++) {
                PetscCall(DMLabelSetValue(perLabel,children[ch],2));
              }
            }
          }
        }
      }
    }
    for (p=fStart;p<fEnd;p++) {
      const PetscInt *support;
      PetscInt       supportSize;
      PetscBool      isbf = PETSC_FALSE;

      PetscCall(DMPlexGetSupportSize(dm,p,&supportSize));
      if (pown) {
        PetscBool has_owned = PETSC_FALSE, has_ghost = PETSC_FALSE;
        PetscInt  i;

        PetscCall(DMPlexGetSupport(dm,p,&support));
        for (i=0;i<supportSize;i++) {
          if (PetscLikely(PetscBTLookup(pown,support[i]-cStart))) has_owned = PETSC_TRUE;
          else has_ghost = PETSC_TRUE;
        }
        isbf = (PetscBool)((supportSize == 1 && has_owned) || (supportSize > 1 && has_owned && has_ghost));
      } else {
        isbf = (PetscBool)(supportSize == 1);
      }
      if (!isbf && perLabel) {
        const PetscInt *cone;
        PetscInt       coneSize,i;

        PetscCall(DMPlexGetCone(dm,p,&cone));
        PetscCall(DMPlexGetConeSize(dm,p,&coneSize));
        isbf = PETSC_TRUE;
        for (i=0;i<coneSize;i++) {
          PetscInt v,d;

          PetscCall(DMLabelGetValue(perLabel,cone[i],&v));
          PetscCall(DMLabelGetDefaultValue(perLabel,&d));
          isbf = (PetscBool)(isbf && v != d);
        }
      }
      if (isbf) {
        PetscCall(PetscBTSet(bfaces,p-fStart));
      }
    }
    /* count boundary faces */
    for (p=fStart,bf=0;p<fEnd;p++) {
      if (PetscUnlikely(PetscBTLookup(bfaces,p-fStart))) {
        const PetscInt *support;
        PetscInt       supportSize,c;

        PetscCall(DMPlexGetSupportSize(dm,p,&supportSize));
        PetscCall(DMPlexGetSupport(dm,p,&support));
        for (c=0;c<supportSize;c++) {
          const    PetscInt *cone;
          PetscInt cell,cl,coneSize;

          cell = support[c];
          if (pown && PetscUnlikely(!PetscBTLookup(pown,cell-cStart))) continue;
          PetscCall(DMPlexGetCone(dm,cell,&cone));
          PetscCall(DMPlexGetConeSize(dm,cell,&coneSize));
          for (cl=0;cl<coneSize;cl++) {
            if (cone[cl] == p) {
              bf += 1;
              break;
            }
          }
        }
      }
    }
    minl = 1;
    label = NULL;
    if (enable_bmark) {
      PetscInt lminl = PETSC_MAX_INT;

      PetscCall(DMGetLabel(dm,bmark,&label));
      if (label) {
        IS       vals;
        PetscInt ldef;

        PetscCall(DMLabelGetDefaultValue(label,&ldef));
        PetscCall(DMLabelGetValueIS(label,&vals));
        PetscCall(ISGetMinMax(vals,&lminl,NULL));
        PetscCall(ISDestroy(&vals));
        lminl = PetscMin(ldef,lminl);
      }
      PetscCall(MPIU_Allreduce(&lminl,&minl,1,MPIU_INT,MPI_MIN,PetscObjectComm((PetscObject)dm)));
      if (minl == PETSC_MAX_INT) minl = 1;
    }
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",bf));
    for (p=fStart;p<fEnd;p++) {
      if (PetscUnlikely(PetscBTLookup(bfaces,p-fStart))) {
        const PetscInt *support;
        PetscInt       supportSize,c,nc = 0;

        PetscCall(DMPlexGetSupportSize(dm,p,&supportSize));
        PetscCall(DMPlexGetSupport(dm,p,&support));
        if (pown) {
          for (c=0;c<supportSize;c++) {
            if (PetscLikely(PetscBTLookup(pown,support[c]-cStart))) {
              fcells[nc++] = support[c];
            }
          }
        } else for (c=0;c<supportSize;c++) fcells[nc++] = support[c];
        for (c=0;c<nc;c++) {
          const DMPolytopeType *faceTypes;
          DMPolytopeType       cellType;
          const PetscInt       *faceSizes,*cone;
          PetscInt             vids[8],*faces,st,i,coneSize,cell,cl,nv,cid = -1,mid = -1;

          cell = fcells[c];
          PetscCall(DMPlexGetCone(dm,cell,&cone));
          PetscCall(DMPlexGetConeSize(dm,cell,&coneSize));
          for (cl=0;cl<coneSize;cl++)
            if (cone[cl] == p)
              break;
          if (cl == coneSize) continue;

          /* face material id and type */
          PetscCall(DMPlexGetPointMFEMCellID_Internal(dm,label,minl,p,&mid,&cid));
          PetscCall(PetscViewerASCIIPrintf(viewer,"%D %D",mid,cid));
          /* vertex ids */
          PetscCall(DMPlexGetCellType(dm,cell,&cellType));
          PetscCall(DMPlexGetPointMFEMVertexIDs_Internal(dm,cell,(localized && !hovec) ? coordSection : NULL,&nv,vids));
          PetscCall(DMPlexGetRawFaces_Internal(dm,cellType,vids,NULL,&faceTypes,&faceSizes,(const PetscInt**)&faces));
          st = 0;
          for (i=0;i<cl;i++) st += faceSizes[i];
          PetscCall(DMPlexInvertCell(faceTypes[cl],faces + st));
          for (i=0;i<faceSizes[cl];i++) {
            PetscCall(PetscViewerASCIIPrintf(viewer," %d",faces[st+i]));
          }
          PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
          PetscCall(DMPlexRestoreRawFaces_Internal(dm,cellType,vids,NULL,&faceTypes,&faceSizes,(const PetscInt**)&faces));
          bf -= 1;
        }
      }
    }
    PetscCheck(!bf,PETSC_COMM_SELF,PETSC_ERR_PLIB,"Remaining boundary faces %D",bf);
    PetscCall(PetscBTDestroy(&bfaces));
    PetscCall(PetscFree(fcells));
  }

  /* mark owned vertices */
  vown = NULL;
  if (pown) {
    PetscCall(PetscBTCreate(vEnd-vStart,&vown));
    for (p=cStart;p<cEnd;p++) {
      PetscInt i,closureSize,*closure = NULL;

      if (PetscUnlikely(!PetscBTLookup(pown,p-cStart))) continue;
      PetscCall(DMPlexGetTransitiveClosure(dm,p,PETSC_TRUE,&closureSize,&closure));
      for (i=0;i<closureSize;i++) {
        const PetscInt pp = closure[2*i];

        if (pp >= vStart && pp < vEnd) {
          PetscCall(PetscBTSet(vown,pp-vStart));
        }
      }
      PetscCall(DMPlexRestoreTransitiveClosure(dm,p,PETSC_TRUE,&closureSize,&closure));
    }
  }

  if (parentSection) {
    PetscInt vp,gvp;

    for (vp=0,p=vStart;p<vEnd;p++) {
      DMLabel  dlabel;
      PetscInt parent,depth;

      if (PetscUnlikely(vown && !PetscBTLookup(vown,p-vStart))) continue;
      PetscCall(DMPlexGetDepthLabel(dm,&dlabel));
      PetscCall(DMLabelGetValue(dlabel,p,&depth));
      PetscCall(DMPlexGetTreeParent(dm,p,&parent,NULL));
      if (parent != p) vp++;
    }
    PetscCall(MPIU_Allreduce(&vp,&gvp,1,MPIU_INT,MPI_SUM,PetscObjectComm((PetscObject)dm)));
    if (gvp) {
      PetscInt  maxsupp;
      PetscBool *skip = NULL;

      PetscCall(PetscViewerASCIIPrintf(viewer,"\nvertex_parents\n"));
      PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",vp));
      PetscCall(DMPlexGetMaxSizes(dm,NULL,&maxsupp));
      PetscCall(PetscMalloc1(maxsupp,&skip));
      for (p=vStart;p<vEnd;p++) {
        DMLabel  dlabel;
        PetscInt parent;

        if (PetscUnlikely(vown && !PetscBTLookup(vown,p-vStart))) continue;
        PetscCall(DMPlexGetDepthLabel(dm,&dlabel));
        PetscCall(DMPlexGetTreeParent(dm,p,&parent,NULL));
        if (parent != p) {
          PetscInt       vids[8] = { -1, -1, -1, -1, -1, -1, -1, -1 }; /* silent overzealous clang static analyzer */
          PetscInt       i,nv,ssize,n,numChildren,depth = -1;
          const PetscInt *children;

          PetscCall(DMPlexGetConeSize(dm,parent,&ssize));
          switch (ssize) {
            case 2: /* edge */
              nv   = 0;
              PetscCall(DMPlexGetPointMFEMVertexIDs_Internal(dm,parent,localized ? coordSection : NULL,&nv,vids));
              PetscCall(PetscViewerASCIIPrintf(viewer,"%D",p-vStart));
              for (i=0;i<nv;i++) {
                PetscCall(PetscViewerASCIIPrintf(viewer," %D",vids[i]));
              }
              PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
              vp--;
              break;
            case 4: /* face */
              PetscCall(DMPlexGetTreeChildren(dm,parent,&numChildren,&children));
              for (n=0;n<numChildren;n++) {
                PetscCall(DMLabelGetValue(dlabel,children[n],&depth));
                if (!depth) {
                  const PetscInt *hvsupp,*hesupp,*cone;
                  PetscInt       hvsuppSize,hesuppSize,coneSize;
                  PetscInt       hv = children[n],he = -1,f;

                  PetscCall(PetscArrayzero(skip,maxsupp));
                  PetscCall(DMPlexGetSupportSize(dm,hv,&hvsuppSize));
                  PetscCall(DMPlexGetSupport(dm,hv,&hvsupp));
                  for (i=0;i<hvsuppSize;i++) {
                    PetscInt ep;
                    PetscCall(DMPlexGetTreeParent(dm,hvsupp[i],&ep,NULL));
                    if (ep != hvsupp[i]) {
                      he = hvsupp[i];
                    } else {
                      skip[i] = PETSC_TRUE;
                    }
                  }
                  PetscCheck(he != -1,PETSC_COMM_SELF,PETSC_ERR_SUP,"Vertex %D support size %D: hanging edge not found",hv,hvsuppSize);
                  PetscCall(DMPlexGetCone(dm,he,&cone));
                  vids[0] = (cone[0] == hv) ? cone[1] : cone[0];
                  PetscCall(DMPlexGetSupportSize(dm,he,&hesuppSize));
                  PetscCall(DMPlexGetSupport(dm,he,&hesupp));
                  for (f=0;f<hesuppSize;f++) {
                    PetscInt j;

                    PetscCall(DMPlexGetCone(dm,hesupp[f],&cone));
                    PetscCall(DMPlexGetConeSize(dm,hesupp[f],&coneSize));
                    for (j=0;j<coneSize;j++) {
                      PetscInt k;
                      for (k=0;k<hvsuppSize;k++) {
                        if (hvsupp[k] == cone[j]) {
                          skip[k] = PETSC_TRUE;
                          break;
                        }
                      }
                    }
                  }
                  for (i=0;i<hvsuppSize;i++) {
                    if (!skip[i]) {
                      PetscCall(DMPlexGetCone(dm,hvsupp[i],&cone));
                      vids[1] = (cone[0] == hv) ? cone[1] : cone[0];
                    }
                  }
                  PetscCall(PetscViewerASCIIPrintf(viewer,"%D",hv-vStart));
                  for (i=0;i<2;i++) {
                    PetscCall(PetscViewerASCIIPrintf(viewer," %D",vids[i]-vStart));
                  }
                  PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
                  vp--;
                }
              }
              break;
            default:
              SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Don't know how to deal with support size %D",ssize);
          }
        }
      }
      PetscCall(PetscFree(skip));
    }
    PetscCheck(!vp,PETSC_COMM_SELF,PETSC_ERR_PLIB,"Unexpected %D hanging vertices",vp);
  }
  PetscCall(PetscBTDestroy(&vown));

  /* vertices */
  if (hovec) { /* higher-order meshes */
    const char *fec;
    PetscInt   i,n,s;
    PetscCall(PetscViewerASCIIPrintf(viewer,"\nvertices\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",vEnd-vStart));
    PetscCall(PetscViewerASCIIPrintf(viewer,"nodes\n"));
    PetscCall(PetscObjectGetName((PetscObject)hovec,&fec));
    PetscCall(PetscViewerASCIIPrintf(viewer,"FiniteElementSpace\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%s\n",fec));
    PetscCall(PetscViewerASCIIPrintf(viewer,"VDim: %D\n",sdim));
    PetscCall(PetscViewerASCIIPrintf(viewer,"Ordering: 1\n\n")); /*Ordering::byVDIM*/
    if (hoSection) {
      DM cdm;

      PetscCall(VecGetDM(hovec,&cdm));
      for (p=cStart;p<cEnd;p++) {
        PetscScalar *vals = NULL;
        PetscInt    csize;

        if (PetscUnlikely(pown && !PetscBTLookup(pown,p-cStart))) continue;
        PetscCall(DMPlexVecGetClosure(cdm,hoSection,hovec,p,&csize,&vals));
        PetscCheck(csize%sdim == 0,PETSC_COMM_SELF,PETSC_ERR_USER,"Size of closure %D incompatible with space dimension %D",csize,sdim);
        for (i=0;i<csize/sdim;i++) {
          for (s=0;s<sdim;s++) {
            PetscCall(PetscViewerASCIIPrintf(viewer,fmt,(double) PetscRealPart(vals[i*sdim+s])));
          }
          PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
        }
        PetscCall(DMPlexVecRestoreClosure(cdm,hoSection,hovec,p,&csize,&vals));
      }
    } else {
      PetscCall(VecGetArrayRead(hovec,&array));
      PetscCall(VecGetLocalSize(hovec,&n));
      PetscCheck(n%sdim == 0,PETSC_COMM_SELF,PETSC_ERR_USER,"Size of local coordinate vector %D incompatible with space dimension %D",n,sdim);
      for (i=0;i<n/sdim;i++) {
        for (s=0;s<sdim;s++) {
          PetscCall(PetscViewerASCIIPrintf(viewer,fmt,(double) PetscRealPart(array[i*sdim+s])));
        }
        PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
      }
      PetscCall(VecRestoreArrayRead(hovec,&array));
    }
  } else {
    PetscCall(VecGetLocalSize(coordinates,&nvert));
    PetscCall(PetscViewerASCIIPrintf(viewer,"\nvertices\n"));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",nvert/sdim));
    PetscCall(PetscViewerASCIIPrintf(viewer,"%D\n",sdim));
    PetscCall(VecGetArrayRead(coordinates,&array));
    for (p=0;p<nvert/sdim;p++) {
      PetscInt s;
      for (s=0;s<sdim;s++) {
        PetscReal v = PetscRealPart(array[p*sdim+s]);

        PetscCall(PetscViewerASCIIPrintf(viewer,fmt,PetscIsInfOrNanReal(v) ? 0.0 : (double) v));
      }
      PetscCall(PetscViewerASCIIPrintf(viewer,"\n"));
    }
    PetscCall(VecRestoreArrayRead(coordinates,&array));
  }
  PetscCall(PetscBTDestroy(&pown));
  PetscCall(VecDestroy(&hovec));
  PetscFunctionReturn(0);
}

PetscErrorCode DMPlexView_GLVis(DM dm, PetscViewer viewer)
{
  PetscFunctionBegin;
  PetscCall(DMView_GLVis(dm,viewer,DMPlexView_GLVis_ASCII));
  PetscFunctionReturn(0);
}