xref: /petsc/src/dm/impls/plex/plexgmsh.c (revision 730356f691fef1270aa21ce63f6c07feb0212308)

#define PETSCDM_DLL
#include <petsc/private/dmpleximpl.h>    /*I   "petscdmplex.h"   I*/
#include <petsc/private/hashmapi.h>

/*@C
  DMPlexCreateGmshFromFile - Create a DMPlex mesh from a Gmsh file

+ comm        - The MPI communicator
. filename    - Name of the Gmsh file
- interpolate - Create faces and edges in the mesh

  Output Parameter:
. dm  - The DM object representing the mesh

  Level: beginner

.seealso: DMPlexCreateFromFile(), DMPlexCreateGmsh(), DMPlexCreate()
@*/
PetscErrorCode DMPlexCreateGmshFromFile(MPI_Comm comm, const char filename[], PetscBool interpolate, DM *dm)
{
  PetscViewer     viewer;
  PetscMPIInt     rank;
  int             fileType;
  PetscViewerType vtype;
  PetscErrorCode  ierr;

  PetscFunctionBegin;
  ierr = MPI_Comm_rank(comm, &rank);CHKERRQ(ierr);

  /* Determine Gmsh file type (ASCII or binary) from file header */
  if (!rank) {
    PetscViewer vheader;
    char        line[PETSC_MAX_PATH_LEN];
    PetscBool   match;
    int         snum;
    float       version;

    ierr = PetscViewerCreate(PETSC_COMM_SELF, &vheader);CHKERRQ(ierr);
    ierr = PetscViewerSetType(vheader, PETSCVIEWERASCII);CHKERRQ(ierr);
    ierr = PetscViewerFileSetMode(vheader, FILE_MODE_READ);CHKERRQ(ierr);
    ierr = PetscViewerFileSetName(vheader, filename);CHKERRQ(ierr);
    /* Read only the first two lines of the Gmsh file */
    ierr = PetscViewerRead(vheader, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    ierr = PetscStrncmp(line, "$MeshFormat", sizeof(line), &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
    ierr = PetscViewerRead(vheader, line, 2, NULL, PETSC_STRING);CHKERRQ(ierr);
    snum = sscanf(line, "%f %d", &version, &fileType);
    if (snum != 2) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unable to parse Gmsh file header: %s", line);
    if (version < 2.0) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file must be at least version 2.0");
    if ((int)version == 3) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file version 3.0 not supported");
    if (version > 4.0) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file must be at most version 4.0");
    ierr = PetscViewerDestroy(&vheader);CHKERRQ(ierr);
  }
  ierr = MPI_Bcast(&fileType, 1, MPI_INT, 0, comm);CHKERRQ(ierr);
  vtype = (fileType == 0) ? PETSCVIEWERASCII : PETSCVIEWERBINARY;

  /* Create appropriate viewer and build plex */
  ierr = PetscViewerCreate(comm, &viewer);CHKERRQ(ierr);
  ierr = PetscViewerSetType(viewer, vtype);CHKERRQ(ierr);
  ierr = PetscViewerFileSetMode(viewer, FILE_MODE_READ);CHKERRQ(ierr);
  ierr = PetscViewerFileSetName(viewer, filename);CHKERRQ(ierr);
  ierr = DMPlexCreateGmsh(comm, viewer, interpolate, dm);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

typedef struct {
  size_t size;
  void   *buffer;
} GmshWorkBuffer;

static PetscErrorCode GmshWorkBufferInit(GmshWorkBuffer *ctx)
{
  PetscFunctionBegin;
  ctx->size   = 0;
  ctx->buffer = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode GmshWorkBufferGet(GmshWorkBuffer *ctx, size_t count, size_t eltsize, void *buf)
{
  size_t         size = count*eltsize;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  if (ctx->size < size) {
    ierr = PetscFree(ctx->buffer);CHKERRQ(ierr);
    ierr = PetscMalloc(size, &ctx->buffer);CHKERRQ(ierr);
    ctx->size = size;
  }
  *(void**)buf = size ? ctx->buffer : NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode GmshWorkBufferFree(GmshWorkBuffer *ctx)
{
  PetscErrorCode ierr;
  PetscFunctionBegin;
  ierr = PetscFree(ctx->buffer);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

typedef struct {
  PetscInt dim;      /* Entity dimension */
  PetscInt id;       /* Entity number */
  double   bbox[6];  /* Bounding box */
  PetscInt numTags;  /* Size of tag array */
  int      tags[4];  /* Tag array */
} GmshEntity;

typedef struct {
  GmshEntity *entity[4];
  PetscHMapI  entityMap[4];
} GmshEntities;

static PetscErrorCode GmshEntitiesCreate(long count[4], GmshEntities **entities)
{
  PetscInt       dim;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscNew(entities);CHKERRQ(ierr);
  for (dim = 0; dim < 4; ++dim) {
    ierr = PetscCalloc1(count[dim], &(*entities)->entity[dim]);CHKERRQ(ierr);
    ierr = PetscHMapICreate(&(*entities)->entityMap[dim]);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode GmshEntitiesAdd(GmshEntities *entities, PetscInt index, PetscInt dim, PetscInt eid, GmshEntity** entity)
{
  PetscErrorCode ierr;
  PetscFunctionBegin;
  ierr = PetscHMapISet(entities->entityMap[dim], eid, index);CHKERRQ(ierr);
  entities->entity[dim][index].dim = dim;
  entities->entity[dim][index].id  = eid;
  if (entity) *entity = &entities->entity[dim][index];
  PetscFunctionReturn(0);
}

static PetscErrorCode GmshEntitiesGet(GmshEntities *entities, PetscInt dim, PetscInt eid, GmshEntity** entity)
{
  PetscInt       index;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscHMapIGet(entities->entityMap[dim], eid, &index);CHKERRQ(ierr);
  *entity = &entities->entity[dim][index];
  PetscFunctionReturn(0);
}

static PetscErrorCode GmshEntitiesDestroy(GmshEntities **entities)
{
  PetscInt       dim;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  if (!*entities) PetscFunctionReturn(0);
  for (dim = 0; dim < 4; ++dim) {
    ierr = PetscFree((*entities)->entity[dim]);CHKERRQ(ierr);
    ierr = PetscHMapIDestroy(&(*entities)->entityMap[dim]);CHKERRQ(ierr);
  }
  ierr = PetscFree((*entities));CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

typedef struct {
  PetscInt dim;      /* Entity dimension */
  PetscInt id;       /* Element number */
  PetscInt cellType; /* Cell type */
  PetscInt numNodes; /* Size of node array */
  int      nodes[8]; /* Node array */
  PetscInt numTags;  /* Size of tag array */
  int      tags[4];  /* Tag array */
} GmshElement;

static PetscErrorCode DMPlexCreateGmsh_ReadNodes_v2(PetscViewer viewer, PetscBool binary, PetscBool byteSwap, int shift, int *numVertices, double **coordinates)
{
  char           line[PETSC_MAX_PATH_LEN];
  int            v, nid, snum;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
  snum = sscanf(line, "%d", numVertices);
  if (snum != 1) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
  ierr = PetscMalloc1(*numVertices*3, coordinates);CHKERRQ(ierr);
  for (v = 0; v < *numVertices; ++v) {
    double *xyz = *coordinates + v*3;
    ierr = PetscViewerRead(viewer, &nid, 1, NULL, PETSC_ENUM);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(&nid, PETSC_ENUM, 1);CHKERRQ(ierr);}
    if (nid != v+shift) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unexpected node number %d should be %d", nid, v+shift);
    ierr = PetscViewerRead(viewer, xyz, 3, NULL, PETSC_DOUBLE);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(xyz, PETSC_DOUBLE, 3);CHKERRQ(ierr);}
  }
  PetscFunctionReturn(0);
}

/* Gmsh elements can be of any dimension/co-dimension, so we need to traverse the
   file contents multiple times to figure out the true number of cells and facets
   in the given mesh. To make this more efficient we read the file contents only
   once and store them in memory, while determining the true number of cells. */
static PetscErrorCode DMPlexCreateGmsh_ReadElements_v2(PetscViewer viewer, PetscBool binary, PetscBool byteSwap, PETSC_UNUSED int shift, int *numCells, GmshElement **gmsh_elems)
{
  char           line[PETSC_MAX_PATH_LEN];
  GmshElement   *elements;
  int            i, c, p, ibuf[1+4+512], snum;
  int            cellType, dim, numNodes, numNodesIgnore, numElem, numTags;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);;
  snum = sscanf(line, "%d", numCells);
  if (snum != 1) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
  ierr = PetscMalloc1(*numCells, &elements);CHKERRQ(ierr);
  for (c = 0; c < *numCells;) {
    ierr = PetscViewerRead(viewer, ibuf, 3, NULL, PETSC_ENUM);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, 3);CHKERRQ(ierr);}
    if (binary) {
      cellType = ibuf[0];
      numElem = ibuf[1];
      numTags = ibuf[2];
    } else {
      elements[c].id = ibuf[0];
      cellType = ibuf[1];
      numTags = ibuf[2];
      numElem = 1;
    }
    /* http://gmsh.info/doc/texinfo/gmsh.html#MSH-ASCII-file-format */
    numNodesIgnore = 0;
    switch (cellType) {
    case 1: /* 2-node line */
      dim = 1;
      numNodes = 2;
      break;
    case 2: /* 3-node triangle */
      dim = 2;
      numNodes = 3;
      break;
    case 3: /* 4-node quadrangle */
      dim = 2;
      numNodes = 4;
      break;
    case 4: /* 4-node tetrahedron */
      dim  = 3;
      numNodes = 4;
      break;
    case 5: /* 8-node hexahedron */
      dim = 3;
      numNodes = 8;
      break;
    case 6: /* 6-node wedge */
      dim = 3;
      numNodes = 6;
      break;
    case 8: /* 3-node 2nd order line */
      dim = 1;
      numNodes = 2;
      numNodesIgnore = 1;
      break;
    case 9: /* 6-node 2nd order triangle */
      dim = 2;
      numNodes = 3;
      numNodesIgnore = 3;
      break;
    case 13: /* 18-node 2nd wedge */
      dim = 3;
      numNodes = 6;
      numNodesIgnore = 12;
      break;
    case 15: /* 1-node vertex */
      dim = 0;
      numNodes = 1;
      break;
    case 7: /* 5-node pyramid */
    case 10: /* 9-node 2nd order quadrangle */
    case 11: /* 10-node 2nd order tetrahedron */
    case 12: /* 27-node 2nd order hexhedron */
    case 14: /* 14-node 2nd order pyramid */
    default:
      SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unsupported Gmsh element type %d", cellType);
    }
    if (binary) {
      const int nint = 1 + numTags + numNodes + numNodesIgnore;
      /* Loop over element blocks */
      for (i = 0; i < numElem; ++i, ++c) {
        ierr = PetscViewerRead(viewer, ibuf, nint, NULL, PETSC_ENUM);CHKERRQ(ierr);
        if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, nint);CHKERRQ(ierr);}
        elements[c].dim = dim;
        elements[c].numNodes = numNodes;
        elements[c].numTags = numTags;
        elements[c].id = ibuf[0];
        elements[c].cellType = cellType;
        for (p = 0; p < numTags; p++) elements[c].tags[p] = ibuf[1 + p];
        for (p = 0; p < numNodes; p++) elements[c].nodes[p] = ibuf[1 + numTags + p];
      }
    } else {
      elements[c].dim = dim;
      elements[c].numNodes = numNodes;
      elements[c].numTags = numTags;
      elements[c].cellType = cellType;
      ierr = PetscViewerRead(viewer, elements[c].tags, elements[c].numTags, NULL, PETSC_ENUM);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, elements[c].nodes, elements[c].numNodes, NULL, PETSC_ENUM);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, ibuf, numNodesIgnore, NULL, PETSC_ENUM);CHKERRQ(ierr);
      c++;
    }
  }
  *gmsh_elems = elements;
  PetscFunctionReturn(0);
}

/*
$Entities
  numPoints(unsigned long) numCurves(unsigned long)
    numSurfaces(unsigned long) numVolumes(unsigned long)
  // points
  tag(int) boxMinX(double) boxMinY(double) boxMinZ(double)
    boxMaxX(double) boxMaxY(double) boxMaxZ(double)
    numPhysicals(unsigned long) phyisicalTag[...](int)
  ...
  // curves
  tag(int) boxMinX(double) boxMinY(double) boxMinZ(double)
     boxMaxX(double) boxMaxY(double) boxMaxZ(double)
     numPhysicals(unsigned long) physicalTag[...](int)
     numBREPVert(unsigned long) tagBREPVert[...](int)
  ...
  // surfaces
  tag(int) boxMinX(double) boxMinY(double) boxMinZ(double)
    boxMaxX(double) boxMaxY(double) boxMaxZ(double)
    numPhysicals(unsigned long) physicalTag[...](int)
    numBREPCurve(unsigned long) tagBREPCurve[...](int)
  ...
  // volumes
  tag(int) boxMinX(double) boxMinY(double) boxMinZ(double)
    boxMaxX(double) boxMaxY(double) boxMaxZ(double)
    numPhysicals(unsigned long) physicalTag[...](int)
    numBREPSurfaces(unsigned long) tagBREPSurfaces[...](int)
  ...
$EndEntities
*/
static PetscErrorCode DMPlexCreateGmsh_ReadEntities_v4(PetscViewer viewer, PetscBool binary, PetscBool byteSwap, GmshEntities **entities)
{
  long           index, num, count[4];
  int            dim, eid, numTags, *ibuf, t;
  GmshEntity     *entity;
  GmshWorkBuffer work;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = GmshWorkBufferInit(&work);CHKERRQ(ierr);
  ierr = PetscViewerRead(viewer, count, 4, NULL, PETSC_LONG);CHKERRQ(ierr);
  if (byteSwap) {ierr = PetscByteSwap(count, PETSC_LONG, 4);CHKERRQ(ierr);}
  ierr = GmshEntitiesCreate(count, entities);CHKERRQ(ierr);
  for (dim = 0; dim < 4; ++dim) {
    for (index = 0; index < count[dim]; ++index) {
      ierr = PetscViewerRead(viewer, &eid, 1, NULL, PETSC_ENUM);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(&eid, PETSC_ENUM, 1);CHKERRQ(ierr);}
      ierr = GmshEntitiesAdd(*entities, (PetscInt)index, dim, eid, &entity);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, entity->bbox, 6, NULL, PETSC_DOUBLE);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(entity->bbox, PETSC_DOUBLE, 6);CHKERRQ(ierr);}
      ierr = PetscViewerRead(viewer, &num, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(&num, PETSC_LONG, 1);CHKERRQ(ierr);}
      ierr = GmshWorkBufferGet(&work, num, sizeof(int), &ibuf);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, ibuf, num, NULL, PETSC_ENUM);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, num);CHKERRQ(ierr);}
      entity->numTags = numTags = (int) PetscMin(num, 4);
      for (t = 0; t < numTags; ++t) entity->tags[t] = ibuf[t];
      if (dim == 0) continue;
      ierr = PetscViewerRead(viewer, &num, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(&num, PETSC_LONG, 1);CHKERRQ(ierr);}
      ierr = GmshWorkBufferGet(&work, num, sizeof(int), &ibuf);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, ibuf, num, NULL, PETSC_ENUM);CHKERRQ(ierr);
      if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, num);CHKERRQ(ierr);}
    }
  }
  ierr = GmshWorkBufferFree(&work);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*
$Nodes
  numEntityBlocks(unsigned long) numNodes(unsigned long)
  tagEntity(int) dimEntity(int) typeNode(int) numNodes(unsigned long)
    tag(int) x(double) y(double) z(double)
    ...
  ...
$EndNodes
*/
static PetscErrorCode DMPlexCreateGmsh_ReadNodes_v4(PetscViewer viewer, PetscBool binary, PetscBool byteSwap, int shift, int *numVertices, double **gmsh_nodes)
{
  long           block, node, v, numEntityBlocks, numTotalNodes, numNodes;
  int            info[3], nid;
  double         *coordinates;
  char           *cbuf;
  GmshWorkBuffer work;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = GmshWorkBufferInit(&work);CHKERRQ(ierr);
  ierr = PetscViewerRead(viewer, &numEntityBlocks, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
  if (byteSwap) {ierr = PetscByteSwap(&numEntityBlocks, PETSC_LONG, 1);CHKERRQ(ierr);}
  ierr = PetscViewerRead(viewer, &numTotalNodes, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
  if (byteSwap) {ierr = PetscByteSwap(&numTotalNodes, PETSC_LONG, 1);CHKERRQ(ierr);}
  ierr = PetscMalloc1(numTotalNodes*3, &coordinates);CHKERRQ(ierr);
  *numVertices = (int)numTotalNodes;
  *gmsh_nodes = coordinates;
  for (v = 0, block = 0; block < numEntityBlocks; ++block) {
    ierr = PetscViewerRead(viewer, info, 3, NULL, PETSC_ENUM);CHKERRQ(ierr);
    ierr = PetscViewerRead(viewer, &numNodes, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(&numNodes, PETSC_LONG, 1);CHKERRQ(ierr);}
    if (binary) {
      int nbytes = sizeof(int) + 3*sizeof(double);
      ierr = GmshWorkBufferGet(&work, numNodes, nbytes, &cbuf);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, cbuf, numNodes*nbytes, NULL, PETSC_CHAR);CHKERRQ(ierr);
      for (node = 0; node < numNodes; ++node, ++v) {
        char *cnid = cbuf + node*nbytes, *cxyz = cnid + sizeof(int);
        double *xyz = coordinates + v*3;
#if !defined(PETSC_WORDS_BIGENDIAN)
        ierr = PetscByteSwap(cnid, PETSC_ENUM, 1);CHKERRQ(ierr);
        ierr = PetscByteSwap(cxyz, PETSC_DOUBLE, 3);CHKERRQ(ierr);
#endif
        ierr = PetscMemcpy(&nid, cnid, sizeof(int));CHKERRQ(ierr);
        ierr = PetscMemcpy(xyz, cxyz, 3*sizeof(double));CHKERRQ(ierr);
        if (byteSwap) {ierr = PetscByteSwap(&nid, PETSC_ENUM, 1);CHKERRQ(ierr);}
        if (byteSwap) {ierr = PetscByteSwap(xyz, PETSC_DOUBLE, 3);CHKERRQ(ierr);}
        if (nid != v+shift) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unexpected node number %d should be %d", nid, v+shift);
      }
    } else {
      for (node = 0; node < numNodes; ++node, ++v) {
        double *xyz = coordinates + v*3;
        ierr = PetscViewerRead(viewer, &nid, 1, NULL, PETSC_ENUM);CHKERRQ(ierr);
        if (byteSwap) {ierr = PetscByteSwap(&nid, PETSC_ENUM, 1);CHKERRQ(ierr);}
        if (nid != v+shift) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unexpected node number %d should be %d", nid, v+shift);
        ierr = PetscViewerRead(viewer, xyz, 3, NULL, PETSC_DOUBLE);CHKERRQ(ierr);
        if (byteSwap) {ierr = PetscByteSwap(xyz, PETSC_DOUBLE, 3);CHKERRQ(ierr);}
      }
    }
  }
  ierr = GmshWorkBufferFree(&work);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*
$Elements
  numEntityBlocks(unsigned long) numElements(unsigned long)
  tagEntity(int) dimEntity(int) typeEle(int) numElements(unsigned long)
    tag(int) numVert[...](int)
    ...
  ...
$EndElements
*/
static PetscErrorCode DMPlexCreateGmsh_ReadElements_v4(PetscViewer viewer, PetscBool binary, PetscBool byteSwap, PETSC_UNUSED int shift, GmshEntities *entities, int *numCells, GmshElement **gmsh_elems)
{
  long           c, block, numEntityBlocks, numTotalElements, elem, numElements;
  int            p, info[3], *ibuf = NULL;
  int            eid, dim, numTags, *tags, cellType, numNodes;
  GmshEntity     *entity;
  GmshElement    *elements;
  GmshWorkBuffer work;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = GmshWorkBufferInit(&work);CHKERRQ(ierr);
  ierr = PetscViewerRead(viewer, &numEntityBlocks, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
  if (byteSwap) {ierr = PetscByteSwap(&numEntityBlocks, PETSC_LONG, 1);CHKERRQ(ierr);}
  ierr = PetscViewerRead(viewer, &numTotalElements, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
  if (byteSwap) {ierr = PetscByteSwap(&numTotalElements, PETSC_LONG, 1);CHKERRQ(ierr);}
  ierr = PetscCalloc1(numTotalElements, &elements);CHKERRQ(ierr);
  *numCells = (int)numTotalElements;
  *gmsh_elems = elements;
  for (c = 0, block = 0; block < numEntityBlocks; ++block) {
    ierr = PetscViewerRead(viewer, info, 3, NULL, PETSC_ENUM);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(info, PETSC_ENUM, 3);CHKERRQ(ierr);}
    eid = info[0]; dim = info[1]; cellType = info[2];
    ierr = GmshEntitiesGet(entities, dim, eid, &entity);CHKERRQ(ierr);
    numTags = entity->numTags;
    tags = entity->tags;
    switch (cellType) {
    case 1: /* 2-node line */
      numNodes = 2;
      break;
    case 2: /* 3-node triangle */
      numNodes = 3; break;
    case 3: /* 4-node quadrangle */
      numNodes = 4;
      break;
    case 4: /* 4-node tetrahedron */
      numNodes = 4;
      break;
    case 5: /* 8-node hexahedron */
      numNodes = 8;
      break;
    case 6: /* 6-node wedge */
      numNodes = 6;
      break;
    case 15: /* 1-node vertex */
      numNodes = 1;
      break;
    default:
      SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unsupported Gmsh element type %d", cellType);
    }
    ierr = PetscViewerRead(viewer, &numElements, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(&numElements, PETSC_LONG, 1);CHKERRQ(ierr);}
    ierr = GmshWorkBufferGet(&work, (1+numNodes)*numElements, sizeof(int), &ibuf);CHKERRQ(ierr);
    ierr = PetscViewerRead(viewer, ibuf, (1+numNodes)*numElements, NULL, PETSC_ENUM);CHKERRQ(ierr);
    if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, (1+numNodes)*numElements);CHKERRQ(ierr);}
    for (elem = 0; elem < numElements; ++elem, ++c) {
      int *id = ibuf + elem*(1+numNodes), *nodes = id + 1;
      GmshElement *element = elements + c;
      element->dim = dim;
      element->cellType = cellType;
      element->numNodes = numNodes;
      element->numTags = numTags;
      element->id = id[0];
      for (p = 0; p < numNodes; p++) element->nodes[p] = nodes[p];
      for (p = 0; p < numTags; p++) element->tags[p] = tags[p];
    }
  }
  ierr = GmshWorkBufferFree(&work);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*@
  DMPlexCreateGmsh - Create a DMPlex mesh from a Gmsh file viewer

  Collective on comm

  Input Parameters:
+ comm  - The MPI communicator
. viewer - The Viewer associated with a Gmsh file
- interpolate - Create faces and edges in the mesh

  Output Parameter:
. dm  - The DM object representing the mesh

  Note: http://www.geuz.org/gmsh/doc/texinfo/#MSH-ASCII-file-format
  and http://www.geuz.org/gmsh/doc/texinfo/#MSH-binary-file-format

  Level: beginner

.keywords: mesh,Gmsh
.seealso: DMPLEX, DMCreate()
@*/
PetscErrorCode DMPlexCreateGmsh(MPI_Comm comm, PetscViewer viewer, PetscBool interpolate, DM *dm)
{
  PetscViewer    parentviewer = NULL;
  double        *coordsIn = NULL;
  GmshEntities  *entities = NULL;
  GmshElement   *gmsh_elem = NULL;
  PetscSection   coordSection;
  Vec            coordinates;
  PetscBT        periodicV = NULL, periodicC = NULL;
  PetscScalar   *coords;
  PetscInt       dim = 0, embedDim = -1, coordSize, c, v, d, r, cell, *periodicMap = NULL, *periodicMapI = NULL, *hybridMap = NULL, cMax = PETSC_DETERMINE;
  int            i, numVertices = 0, numCells = 0, trueNumCells = 0, numRegions = 0, snum, shift = 1;
  PetscMPIInt    rank;
  char           line[PETSC_MAX_PATH_LEN];
  PetscBool      binary, byteSwap = PETSC_FALSE, zerobase = PETSC_FALSE, periodic = PETSC_FALSE, usemarker = PETSC_FALSE;
  PetscBool      enable_hybrid = PETSC_FALSE;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = MPI_Comm_rank(comm, &rank);CHKERRQ(ierr);
  ierr = PetscOptionsGetBool(((PetscObject) viewer)->options,((PetscObject) viewer)->prefix, "-dm_plex_gmsh_hybrid", &enable_hybrid, NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetBool(((PetscObject) viewer)->options,((PetscObject) viewer)->prefix, "-dm_plex_gmsh_periodic", &periodic, NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetBool(((PetscObject) viewer)->options,((PetscObject) viewer)->prefix, "-dm_plex_gmsh_use_marker", &usemarker, NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetBool(((PetscObject) viewer)->options,((PetscObject) viewer)->prefix, "-dm_plex_gmsh_zero_base", &zerobase, NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetInt(((PetscObject) viewer)->options,((PetscObject) viewer)->prefix, "-dm_plex_gmsh_spacedim", &embedDim, NULL);CHKERRQ(ierr);
  if (zerobase) shift = 0;

  ierr = DMCreate(comm, dm);CHKERRQ(ierr);
  ierr = DMSetType(*dm, DMPLEX);CHKERRQ(ierr);
  ierr = PetscLogEventBegin(DMPLEX_CreateGmsh,*dm,0,0,0);CHKERRQ(ierr);

  ierr = PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERBINARY, &binary);CHKERRQ(ierr);

  /* Binary viewers read on all ranks, get subviewer to read only in rank 0 */
  if (binary) {
    parentviewer = viewer;
    ierr = PetscViewerGetSubViewer(parentviewer, PETSC_COMM_SELF, &viewer);CHKERRQ(ierr);
  }

  if (!rank) {
    PetscBool match, hybrid;
    int       fileType, fileFormat, dataSize;
    float     version;

    /* Read header */
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    ierr = PetscStrncmp(line, "$MeshFormat", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
    ierr = PetscViewerRead(viewer, line, 3, NULL, PETSC_STRING);CHKERRQ(ierr);
    snum = sscanf(line, "%f %d %d", &version, &fileType, &dataSize);
    if (snum != 3) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Unable to parse Gmsh file header: %s", line);
    if (version < 2.0) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file must be at least version 2.0");
    if ((int)version == 3) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file version 3.0 not supported");
    if (version > 4.0) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Gmsh file must be at most version 4.0");
    if (dataSize != sizeof(double)) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Data size %d is not valid for a Gmsh file", dataSize);
    fileFormat = (int)version;
    if (binary) {
      int checkInt;
      ierr = PetscViewerRead(viewer, &checkInt, 1, NULL, PETSC_ENUM);CHKERRQ(ierr);
      if (checkInt != 1) {
        ierr = PetscByteSwap(&checkInt, PETSC_ENUM, 1);CHKERRQ(ierr);
        if (checkInt == 1) byteSwap = PETSC_TRUE;
        else SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File type %d is not a valid Gmsh binary file", fileType);
      }
    } else if (fileType) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File type %d is not a valid Gmsh ASCII file", fileType);
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    ierr = PetscStrncmp(line, "$EndMeshFormat", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");

    /* OPTIONAL Read physical names */
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    ierr = PetscStrncmp(line, "$PhysicalNames", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (match) {
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
      snum = sscanf(line, "%d", &numRegions);
      if (snum != 1) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      for (r = 0; r < numRegions; ++r) {
        ierr = PetscViewerRead(viewer, line, 3, NULL, PETSC_STRING);CHKERRQ(ierr);
      }
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
      ierr = PetscStrncmp(line, "$EndPhysicalNames", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
      if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      /* Initial read for vertex section */
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    }

    /* Read entities */
    if (fileFormat == 4) {
      ierr = PetscStrncmp(line, "$Entities", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
      if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      ierr = DMPlexCreateGmsh_ReadEntities_v4(viewer, binary, byteSwap, &entities);CHKERRQ(ierr);
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
      ierr = PetscStrncmp(line, "$EndEntities", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
      if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    }

    /* Read vertices */
    ierr = PetscStrncmp(line, "$Nodes", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
    if (fileFormat == 2) {
      ierr = DMPlexCreateGmsh_ReadNodes_v2(viewer, binary, byteSwap, shift, &numVertices, &coordsIn);CHKERRQ(ierr);
    } else {
      ierr = DMPlexCreateGmsh_ReadNodes_v4(viewer, binary, byteSwap, shift, &numVertices, &coordsIn);CHKERRQ(ierr);
    }
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);;
    ierr = PetscStrncmp(line, "$EndNodes", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");

    /* Read cells */
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);;
    ierr = PetscStrncmp(line, "$Elements", PETSC_MAX_PATH_LEN, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
    if (fileFormat == 2) {
      ierr = DMPlexCreateGmsh_ReadElements_v2(viewer, binary, byteSwap, shift, &numCells, &gmsh_elem);CHKERRQ(ierr);
    } else {
      ierr = DMPlexCreateGmsh_ReadElements_v4(viewer, binary, byteSwap, shift, entities, &numCells, &gmsh_elem);CHKERRQ(ierr);
    }
    ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
    ierr = PetscStrncmp(line, "$EndElements", 12, &match);CHKERRQ(ierr);
    if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");

    ierr = GmshEntitiesDestroy(&entities);CHKERRQ(ierr);

    hybrid = PETSC_FALSE;
    for (trueNumCells = 0, c = 0; c < numCells; ++c) {
      int on = -1;
      if (gmsh_elem[c].dim > dim) {dim = gmsh_elem[c].dim; trueNumCells = 0;}
      if (gmsh_elem[c].dim == dim) {hybrid = (trueNumCells ? (on != gmsh_elem[c].cellType ? on = gmsh_elem[c].cellType,PETSC_TRUE : hybrid) : (on = gmsh_elem[c].cellType, PETSC_FALSE) ); trueNumCells++;}
      /* wedges always indicate an hybrid mesh in PLEX */
      if (on == 6 || on == 13) hybrid = PETSC_TRUE;
    }

    /* Renumber cells for hybrid grids */
    if (hybrid && enable_hybrid) {
      PetscInt hc1 = 0, hc2 = 0, *hybridCells1 = NULL, *hybridCells2 = NULL;
      PetscInt cell, tn, *tp;
      int      n1 = 0,n2 = 0;

      ierr = PetscMalloc1(trueNumCells, &hybridCells1);CHKERRQ(ierr);
      ierr = PetscMalloc1(trueNumCells, &hybridCells2);CHKERRQ(ierr);
      for (cell = 0, c = 0; c < numCells; ++c) {
        if (gmsh_elem[c].dim == dim) {
          if (!n1) n1 = gmsh_elem[c].cellType;
          else if (!n2 && n1 != gmsh_elem[c].cellType) n2 = gmsh_elem[c].cellType;

          if      (gmsh_elem[c].cellType == n1) hybridCells1[hc1++] = cell;
          else if (gmsh_elem[c].cellType == n2) hybridCells2[hc2++] = cell;
          else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_SUP, "Cannot handle more than 2 cell types");
          cell++;
        }
      }

      switch (n1) {
      case 2: /* triangles */
      case 9:
        switch (n2) {
        case 0: /* single type mesh */
        case 3: /* quads */
        case 10:
          break;
        default:
          SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported cell types %d and %d",n1, n2);
        }
        break;
      case 3:
      case 10:
        switch (n2) {
        case 0: /* single type mesh */
        case 2: /* swap since we list simplices first */
        case 9:
          tn  = hc1;
          hc1 = hc2;
          hc2 = tn;

          tp           = hybridCells1;
          hybridCells1 = hybridCells2;
          hybridCells2 = tp;
          break;
        default:
          SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported cell types %d and %d",n1, n2);
        }
        break;
      case 4: /* tetrahedra */
      case 11:
        switch (n2) {
        case 0: /* single type mesh */
        case 6: /* wedges */
        case 13:
          break;
        default:
          SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported cell types %d and %d",n1, n2);
        }
        break;
      case 6:
      case 13:
        switch (n2) {
        case 0: /* single type mesh */
        case 4: /* swap since we list simplices first */
        case 11:
          tn  = hc1;
          hc1 = hc2;
          hc2 = tn;

          tp           = hybridCells1;
          hybridCells1 = hybridCells2;
          hybridCells2 = tp;
          break;
        default:
          SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported cell types %d and %d",n1, n2);
        }
        break;
      default:
        SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_SUP, "Unsupported cell types %d and %d",n1, n2);
      }
      cMax = hc1;
      ierr = PetscMalloc1(trueNumCells, &hybridMap);CHKERRQ(ierr);
      for (cell = 0; cell < hc1; cell++) hybridMap[hybridCells1[cell]] = cell;
      for (cell = 0; cell < hc2; cell++) hybridMap[hybridCells2[cell]] = cell + hc1;
      ierr = PetscFree(hybridCells1);CHKERRQ(ierr);
      ierr = PetscFree(hybridCells2);CHKERRQ(ierr);
    }

    /* OPTIONAL Read periodic section */
    if (periodic) {
      PetscInt pVert, *periodicMapT, *aux;
      int      numPeriodic;

      ierr = PetscMalloc1(numVertices, &periodicMapT);CHKERRQ(ierr);
      ierr = PetscBTCreate(numVertices, &periodicV);CHKERRQ(ierr);
      for (i = 0; i < numVertices; i++) periodicMapT[i] = i;

      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
      ierr = PetscStrncmp(line, "$Periodic", 9, &match);CHKERRQ(ierr);
      if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      if (fileFormat == 2 || !binary) {
        ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
        snum = sscanf(line, "%d", &numPeriodic);
        if (snum != 1) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
      } else {
        ierr = PetscViewerRead(viewer, &numPeriodic, 1, NULL, PETSC_ENUM);CHKERRQ(ierr);
        if (byteSwap) {ierr = PetscByteSwap(&numPeriodic, PETSC_ENUM, 1);CHKERRQ(ierr);}
      }
      for (i = 0; i < numPeriodic; i++) {
        int    ibuf[3], slaveDim = -1, slaveTag = -1, masterTag = -1, slaveNode, masterNode;
        long   j, nNodes;
        double affine[16];

        if (fileFormat == 2 || !binary) {
          ierr = PetscViewerRead(viewer, line, 3, NULL, PETSC_STRING);CHKERRQ(ierr);
          snum = sscanf(line, "%d %d %d", &slaveDim, &slaveTag, &masterTag);
          if (snum != 3) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
        } else {
          ierr = PetscViewerRead(viewer, ibuf, 3, NULL, PETSC_ENUM);CHKERRQ(ierr);
          if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, 3);CHKERRQ(ierr);}
          slaveDim = ibuf[0]; slaveTag = ibuf[1]; masterTag = ibuf[2];
        }
        (void)slaveDim; (void)slaveTag; (void)masterTag; /* unused */

        if (fileFormat == 2 || !binary) {
          ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
          snum = sscanf(line, "%ld", &nNodes);
          if (snum != 1) { /* discard tranformation and try again */
            ierr = PetscViewerRead(viewer, line, -PETSC_MAX_PATH_LEN, NULL, PETSC_STRING);CHKERRQ(ierr);
            ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
            snum = sscanf(line, "%ld", &nNodes);
            if (snum != 1) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
          }
        } else {
          ierr = PetscViewerRead(viewer, &nNodes, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
          if (byteSwap) {ierr = PetscByteSwap(&nNodes, PETSC_LONG, 1);CHKERRQ(ierr);}
          if (nNodes == -1) { /* discard tranformation and try again */
            ierr = PetscViewerRead(viewer, affine, 16, NULL, PETSC_DOUBLE);CHKERRQ(ierr);
            ierr = PetscViewerRead(viewer, &nNodes, 1, NULL, PETSC_LONG);CHKERRQ(ierr);
            if (byteSwap) {ierr = PetscByteSwap(&nNodes, PETSC_LONG, 1);CHKERRQ(ierr);}
          }
        }

        for (j = 0; j < nNodes; j++) {
          if (fileFormat == 2 || !binary) {
            ierr = PetscViewerRead(viewer, line, 2, NULL, PETSC_STRING);CHKERRQ(ierr);
            snum = sscanf(line, "%d %d", &slaveNode, &masterNode);
            if (snum != 2) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");
          } else {
            ierr = PetscViewerRead(viewer, ibuf, 2, NULL, PETSC_ENUM);CHKERRQ(ierr);
            if (byteSwap) {ierr = PetscByteSwap(ibuf, PETSC_ENUM, 2);CHKERRQ(ierr);}
            slaveNode = ibuf[0]; masterNode = ibuf[1];
          }
          periodicMapT[slaveNode - shift] = masterNode - shift;
          ierr = PetscBTSet(periodicV, slaveNode - shift);CHKERRQ(ierr);
          ierr = PetscBTSet(periodicV, masterNode - shift);CHKERRQ(ierr);
        }
      }
      ierr = PetscViewerRead(viewer, line, 1, NULL, PETSC_STRING);CHKERRQ(ierr);
      ierr = PetscStrncmp(line, "$EndPeriodic", 12, &match);CHKERRQ(ierr);
      if (!match) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "File is not a valid Gmsh file");

      /* we may have slaves of slaves */
      for (i = 0; i < numVertices; i++) {
        while (periodicMapT[periodicMapT[i]] != periodicMapT[i]) {
          periodicMapT[i] = periodicMapT[periodicMapT[i]];
        }
      }
      /* periodicMap : from old to new numbering (periodic vertices excluded)
         periodicMapI: from new to old numbering */
      ierr = PetscMalloc1(numVertices, &periodicMap);CHKERRQ(ierr);
      ierr = PetscMalloc1(numVertices, &periodicMapI);CHKERRQ(ierr);
      ierr = PetscMalloc1(numVertices, &aux);CHKERRQ(ierr);
      for (i = 0, pVert = 0; i < numVertices; i++) {
        if (periodicMapT[i] != i) {
          pVert++;
        } else {
          aux[i] = i - pVert;
          periodicMapI[i - pVert] = i;
        }
      }
      for (i = 0 ; i < numVertices; i++) {
        periodicMap[i] = aux[periodicMapT[i]];
      }
      ierr = PetscFree(periodicMapT);CHKERRQ(ierr);
      ierr = PetscFree(aux);CHKERRQ(ierr);
      /* remove periodic vertices */
      numVertices = numVertices - pVert;
    }
  }

  if (parentviewer) {
    ierr = PetscViewerRestoreSubViewer(parentviewer, PETSC_COMM_SELF, &viewer);CHKERRQ(ierr);
  }

  /* Allocate the cell-vertex mesh */
  ierr = DMPlexSetChart(*dm, 0, trueNumCells+numVertices);CHKERRQ(ierr);
  for (cell = 0, c = 0; c < numCells; ++c) {
    if (gmsh_elem[c].dim == dim) {
      ierr = DMPlexSetConeSize(*dm, hybridMap ? hybridMap[cell] : cell, gmsh_elem[c].numNodes);CHKERRQ(ierr);
      cell++;
    }
  }
  ierr = DMSetUp(*dm);CHKERRQ(ierr);
  /* Add cell-vertex connections */
  for (cell = 0, c = 0; c < numCells; ++c) {
    if (gmsh_elem[c].dim == dim) {
      PetscInt pcone[8], corner;
      for (corner = 0; corner < gmsh_elem[c].numNodes; ++corner) {
        const PetscInt cc = gmsh_elem[c].nodes[corner] - shift;
        pcone[corner] = (periodicMap ? periodicMap[cc] : cc) + trueNumCells;
      }
      if (dim == 3) {
        /* Tetrahedra are inverted */
        if (gmsh_elem[c].cellType == 4) {
          PetscInt tmp = pcone[0];
          pcone[0] = pcone[1];
          pcone[1] = tmp;
        }
        /* Hexahedra are inverted */
        if (gmsh_elem[c].cellType == 5) {
          PetscInt tmp = pcone[1];
          pcone[1] = pcone[3];
          pcone[3] = tmp;
        }
        /* Prisms are inverted */
        if (gmsh_elem[c].cellType == 6) {
          PetscInt tmp;

          tmp      = pcone[1];
          pcone[1] = pcone[2];
          pcone[2] = tmp;
          tmp      = pcone[4];
          pcone[4] = pcone[5];
          pcone[5] = tmp;
        }
      } else if (dim == 2 && hybridMap && hybridMap[cell] >= cMax) { /* hybrid cells */
        /* quads are input to PLEX as prisms */
        if (gmsh_elem[c].cellType == 3) {
          PetscInt tmp = pcone[2];
          pcone[2] = pcone[3];
          pcone[3] = tmp;
        }
      }
      ierr = DMPlexSetCone(*dm, hybridMap ? hybridMap[cell] : cell, pcone);CHKERRQ(ierr);
      cell++;
    }
  }
  ierr = MPI_Bcast(&dim, 1, MPIU_INT, 0, comm);CHKERRQ(ierr);
  ierr = DMSetDimension(*dm, dim);CHKERRQ(ierr);
  ierr = DMPlexSetHybridBounds(*dm, cMax, PETSC_DETERMINE, PETSC_DETERMINE, PETSC_DETERMINE);CHKERRQ(ierr);
  ierr = DMPlexSymmetrize(*dm);CHKERRQ(ierr);
  ierr = DMPlexStratify(*dm);CHKERRQ(ierr);
  if (interpolate) {
    DM idm;

    ierr = DMPlexInterpolate(*dm, &idm);CHKERRQ(ierr);
    ierr = DMDestroy(dm);CHKERRQ(ierr);
    *dm  = idm;
  }

  if (usemarker && !interpolate && dim > 1) SETERRQ(comm,PETSC_ERR_SUP,"Cannot create marker label without interpolation");
  if (!rank && usemarker) {
    PetscInt f, fStart, fEnd;

    ierr = DMCreateLabel(*dm, "marker");CHKERRQ(ierr);
    ierr = DMPlexGetHeightStratum(*dm, 1, &fStart, &fEnd);CHKERRQ(ierr);
    for (f = fStart; f < fEnd; ++f) {
      PetscInt suppSize;

      ierr = DMPlexGetSupportSize(*dm, f, &suppSize);CHKERRQ(ierr);
      if (suppSize == 1) {
        PetscInt *cone = NULL, coneSize, p;

        ierr = DMPlexGetTransitiveClosure(*dm, f, PETSC_TRUE, &coneSize, &cone);CHKERRQ(ierr);
        for (p = 0; p < coneSize; p += 2) {
          ierr = DMSetLabelValue(*dm, "marker", cone[p], 1);CHKERRQ(ierr);
        }
        ierr = DMPlexRestoreTransitiveClosure(*dm, f, PETSC_TRUE, &coneSize, &cone);CHKERRQ(ierr);
      }
    }
  }

  if (!rank) {
    PetscInt vStart, vEnd;

    ierr = DMPlexGetDepthStratum(*dm, 0, &vStart, &vEnd);CHKERRQ(ierr);
    for (cell = 0, c = 0; c < numCells; ++c) {

      /* Create face sets */
      if (interpolate && gmsh_elem[c].dim == dim-1) {
        const PetscInt *join;
        PetscInt        joinSize, pcone[8], corner;
        /* Find the relevant facet with vertex joins */
        for (corner = 0; corner < gmsh_elem[c].numNodes; ++corner) {
          const PetscInt cc = gmsh_elem[c].nodes[corner] - shift;
          pcone[corner] = (periodicMap ? periodicMap[cc] : cc) + vStart;
        }
        ierr = DMPlexGetFullJoin(*dm, gmsh_elem[c].numNodes, pcone, &joinSize, &join);CHKERRQ(ierr);
        if (joinSize != 1) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Could not determine Plex facet for GMsh element %d (Plex cell %D)", gmsh_elem[c].id, c);
        ierr = DMSetLabelValue(*dm, "Face Sets", join[0], gmsh_elem[c].tags[0]);CHKERRQ(ierr);
        ierr = DMPlexRestoreJoin(*dm, gmsh_elem[c].numNodes, (const PetscInt *) pcone, &joinSize, &join);CHKERRQ(ierr);
      }

      /* Create cell sets */
      if (gmsh_elem[c].dim == dim) {
        if (gmsh_elem[c].numTags > 0) {
          ierr = DMSetLabelValue(*dm, "Cell Sets", hybridMap ? hybridMap[cell] : cell, gmsh_elem[c].tags[0]);CHKERRQ(ierr);
        }
        cell++;
      }

      /* Create vertex sets */
      if (gmsh_elem[c].dim == 0) {
        if (gmsh_elem[c].numTags > 0) {
          const PetscInt cc = gmsh_elem[c].nodes[0] - shift;
          const PetscInt vid = (periodicMap ? periodicMap[cc] : cc) + vStart;
          ierr = DMSetLabelValue(*dm, "Vertex Sets", vid, gmsh_elem[c].tags[0]);CHKERRQ(ierr);
        }
      }
    }
  }

  /* Create coordinates */
  if (embedDim < 0) embedDim = dim;
  ierr = DMSetCoordinateDim(*dm, embedDim);CHKERRQ(ierr);
  ierr = DMGetCoordinateSection(*dm, &coordSection);CHKERRQ(ierr);
  ierr = PetscSectionSetNumFields(coordSection, 1);CHKERRQ(ierr);
  ierr = PetscSectionSetFieldComponents(coordSection, 0, embedDim);CHKERRQ(ierr);
  if (periodicMap) { /* we need to localize coordinates on cells */
    ierr = PetscSectionSetChart(coordSection, 0, trueNumCells + numVertices);CHKERRQ(ierr);
  } else {
    ierr = PetscSectionSetChart(coordSection, trueNumCells, trueNumCells + numVertices);CHKERRQ(ierr);
  }
  for (v = trueNumCells; v < trueNumCells+numVertices; ++v) {
    ierr = PetscSectionSetDof(coordSection, v, embedDim);CHKERRQ(ierr);
    ierr = PetscSectionSetFieldDof(coordSection, v, 0, embedDim);CHKERRQ(ierr);
  }
  if (periodicMap) {
    ierr = PetscBTCreate(trueNumCells, &periodicC);CHKERRQ(ierr);
    for (cell = 0, c = 0; c < numCells; ++c) {
      if (gmsh_elem[c].dim == dim) {
        PetscInt  corner;
        PetscBool pc = PETSC_FALSE;
        for (corner = 0; corner < gmsh_elem[c].numNodes; ++corner) {
          pc = (PetscBool)(pc || PetscBTLookup(periodicV, gmsh_elem[c].nodes[corner] - shift));
        }
        if (pc) {
          PetscInt dof = gmsh_elem[c].numNodes*embedDim;
          PetscInt ucell = hybridMap ? hybridMap[cell] : cell;
          ierr = PetscBTSet(periodicC, ucell);CHKERRQ(ierr);
          ierr = PetscSectionSetDof(coordSection, ucell, dof);CHKERRQ(ierr);
          ierr = PetscSectionSetFieldDof(coordSection, ucell, 0, dof);CHKERRQ(ierr);
        }
        cell++;
      }
    }
  }
  ierr = PetscSectionSetUp(coordSection);CHKERRQ(ierr);
  ierr = PetscSectionGetStorageSize(coordSection, &coordSize);CHKERRQ(ierr);
  ierr = VecCreate(PETSC_COMM_SELF, &coordinates);CHKERRQ(ierr);
  ierr = PetscObjectSetName((PetscObject) coordinates, "coordinates");CHKERRQ(ierr);
  ierr = VecSetSizes(coordinates, coordSize, PETSC_DETERMINE);CHKERRQ(ierr);
  ierr = VecSetBlockSize(coordinates, embedDim);CHKERRQ(ierr);
  ierr = VecSetType(coordinates, VECSTANDARD);CHKERRQ(ierr);
  ierr = VecGetArray(coordinates, &coords);CHKERRQ(ierr);
  if (periodicMap) {
    PetscInt off;

    for (cell = 0, c = 0; c < numCells; ++c) {
      PetscInt pcone[8], corner;
      if (gmsh_elem[c].dim == dim) {
        PetscInt ucell = hybridMap ? hybridMap[cell] : cell;
        if (PetscUnlikely(PetscBTLookup(periodicC, ucell))) {
          for (corner = 0; corner < gmsh_elem[c].numNodes; ++corner) {
            pcone[corner] = gmsh_elem[c].nodes[corner] - shift;
          }
          if (dim == 3) {
            /* Tetrahedra are inverted */
            if (gmsh_elem[c].cellType == 4) {
              PetscInt tmp = pcone[0];
              pcone[0] = pcone[1];
              pcone[1] = tmp;
            }
            /* Hexahedra are inverted */
            if (gmsh_elem[c].cellType == 5) {
              PetscInt tmp = pcone[1];
              pcone[1] = pcone[3];
              pcone[3] = tmp;
            }
            /* Prisms are inverted */
            if (gmsh_elem[c].cellType == 6) {
              PetscInt tmp;

              tmp      = pcone[1];
              pcone[1] = pcone[2];
              pcone[2] = tmp;
              tmp      = pcone[4];
              pcone[4] = pcone[5];
              pcone[5] = tmp;
            }
          } else if (dim == 2 && hybridMap && hybridMap[cell] >= cMax) { /* hybrid cells */
            /* quads are input to PLEX as prisms */
            if (gmsh_elem[c].cellType == 3) {
              PetscInt tmp = pcone[2];
              pcone[2] = pcone[3];
              pcone[3] = tmp;
            }
          }
          ierr = PetscSectionGetOffset(coordSection, ucell, &off);CHKERRQ(ierr);
          for (corner = 0; corner < gmsh_elem[c].numNodes; ++corner) {
            v = pcone[corner];
            for (d = 0; d < embedDim; ++d) {
              coords[off++] = (PetscReal) coordsIn[v*3+d];
            }
          }
        }
        cell++;
      }
    }
    for (v = 0; v < numVertices; ++v) {
      ierr = PetscSectionGetOffset(coordSection, v + trueNumCells, &off);CHKERRQ(ierr);
      for (d = 0; d < embedDim; ++d) {
        coords[off+d] = (PetscReal) coordsIn[periodicMapI[v]*3+d];
      }
    }
  } else {
    for (v = 0; v < numVertices; ++v) {
      for (d = 0; d < embedDim; ++d) {
        coords[v*embedDim+d] = (PetscReal) coordsIn[v*3+d];
      }
    }
  }
  ierr = VecRestoreArray(coordinates, &coords);CHKERRQ(ierr);
  ierr = DMSetCoordinatesLocal(*dm, coordinates);CHKERRQ(ierr);
  ierr = DMSetPeriodicity(*dm, periodic, NULL, NULL, NULL);CHKERRQ(ierr);

  ierr = PetscFree(coordsIn);CHKERRQ(ierr);
  ierr = PetscFree(gmsh_elem);CHKERRQ(ierr);
  ierr = PetscFree(hybridMap);CHKERRQ(ierr);
  ierr = PetscFree(periodicMap);CHKERRQ(ierr);
  ierr = PetscFree(periodicMapI);CHKERRQ(ierr);
  ierr = PetscBTDestroy(&periodicV);CHKERRQ(ierr);
  ierr = PetscBTDestroy(&periodicC);CHKERRQ(ierr);
  ierr = VecDestroy(&coordinates);CHKERRQ(ierr);

  ierr = PetscLogEventEnd(DMPLEX_CreateGmsh,*dm,0,0,0);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}