xref: /petsc/src/dm/impls/plex/plexpartition.c (revision c73cfb54f34510b9dcefc99e398efa3b88d5dde5)

#include <petsc-private/dmpleximpl.h>   /*I      "petscdmplex.h"   I*/

#undef __FUNCT__
#define __FUNCT__ "DMPlexCreateNeighborCSR"
PetscErrorCode DMPlexCreateNeighborCSR(DM dm, PetscInt cellHeight, PetscInt *numVertices, PetscInt **offsets, PetscInt **adjacency)
{
  const PetscInt maxFaceCases = 30;
  PetscInt       numFaceCases = 0;
  PetscInt       numFaceVertices[30]; /* maxFaceCases, C89 sucks sucks sucks */
  PetscInt      *off, *adj;
  PetscInt      *neighborCells = NULL;
  PetscInt       dim, cellDim, depth = 0, faceDepth, cStart, cEnd, c, numCells, cell;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  /* For parallel partitioning, I think you have to communicate supports */
  ierr = DMGetDimension(dm, &dim);CHKERRQ(ierr);
  cellDim = dim - cellHeight;
  ierr = DMPlexGetDepth(dm, &depth);CHKERRQ(ierr);
  ierr = DMPlexGetHeightStratum(dm, cellHeight, &cStart, &cEnd);CHKERRQ(ierr);
  if (cEnd - cStart == 0) {
    if (numVertices) *numVertices = 0;
    if (offsets)   *offsets   = NULL;
    if (adjacency) *adjacency = NULL;
    PetscFunctionReturn(0);
  }
  numCells  = cEnd - cStart;
  faceDepth = depth - cellHeight;
  if (dim == depth) {
    PetscInt f, fStart, fEnd;

    ierr = PetscCalloc1(numCells+1, &off);CHKERRQ(ierr);
    /* Count neighboring cells */
    ierr = DMPlexGetHeightStratum(dm, cellHeight+1, &fStart, &fEnd);CHKERRQ(ierr);
    for (f = fStart; f < fEnd; ++f) {
      const PetscInt *support;
      PetscInt        supportSize;
      ierr = DMPlexGetSupportSize(dm, f, &supportSize);CHKERRQ(ierr);
      ierr = DMPlexGetSupport(dm, f, &support);CHKERRQ(ierr);
      if (supportSize == 2) {
        ++off[support[0]-cStart+1];
        ++off[support[1]-cStart+1];
      }
    }
    /* Prefix sum */
    for (c = 1; c <= numCells; ++c) off[c] += off[c-1];
    if (adjacency) {
      PetscInt *tmp;

      ierr = PetscMalloc1(off[numCells], &adj);CHKERRQ(ierr);
      ierr = PetscMalloc1((numCells+1), &tmp);CHKERRQ(ierr);
      ierr = PetscMemcpy(tmp, off, (numCells+1) * sizeof(PetscInt));CHKERRQ(ierr);
      /* Get neighboring cells */
      for (f = fStart; f < fEnd; ++f) {
        const PetscInt *support;
        PetscInt        supportSize;
        ierr = DMPlexGetSupportSize(dm, f, &supportSize);CHKERRQ(ierr);
        ierr = DMPlexGetSupport(dm, f, &support);CHKERRQ(ierr);
        if (supportSize == 2) {
          adj[tmp[support[0]-cStart]++] = support[1];
          adj[tmp[support[1]-cStart]++] = support[0];
        }
      }
#if defined(PETSC_USE_DEBUG)
      for (c = 0; c < cEnd-cStart; ++c) if (tmp[c] != off[c+1]) SETERRQ3(PETSC_COMM_SELF, PETSC_ERR_PLIB, "Offset %d != %d for cell %d", tmp[c], off[c], c+cStart);
#endif
      ierr = PetscFree(tmp);CHKERRQ(ierr);
    }
    if (numVertices) *numVertices = numCells;
    if (offsets)   *offsets   = off;
    if (adjacency) *adjacency = adj;
    PetscFunctionReturn(0);
  }
  /* Setup face recognition */
  if (faceDepth == 1) {
    PetscInt cornersSeen[30] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; /* Could use PetscBT */

    for (c = cStart; c < cEnd; ++c) {
      PetscInt corners;

      ierr = DMPlexGetConeSize(dm, c, &corners);CHKERRQ(ierr);
      if (!cornersSeen[corners]) {
        PetscInt nFV;

        if (numFaceCases >= maxFaceCases) SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_PLIB, "Exceeded maximum number of face recognition cases");
        cornersSeen[corners] = 1;

        ierr = DMPlexGetNumFaceVertices(dm, cellDim, corners, &nFV);CHKERRQ(ierr);

        numFaceVertices[numFaceCases++] = nFV;
      }
    }
  }
  ierr = PetscCalloc1(numCells+1, &off);CHKERRQ(ierr);
  /* Count neighboring cells */
  for (cell = cStart; cell < cEnd; ++cell) {
    PetscInt numNeighbors = PETSC_DETERMINE, n;

    ierr = DMPlexGetAdjacency_Internal(dm, cell, PETSC_TRUE, PETSC_FALSE, &numNeighbors, &neighborCells);CHKERRQ(ierr);
    /* Get meet with each cell, and check with recognizer (could optimize to check each pair only once) */
    for (n = 0; n < numNeighbors; ++n) {
      PetscInt        cellPair[2];
      PetscBool       found    = faceDepth > 1 ? PETSC_TRUE : PETSC_FALSE;
      PetscInt        meetSize = 0;
      const PetscInt *meet    = NULL;

      cellPair[0] = cell; cellPair[1] = neighborCells[n];
      if (cellPair[0] == cellPair[1]) continue;
      if (!found) {
        ierr = DMPlexGetMeet(dm, 2, cellPair, &meetSize, &meet);CHKERRQ(ierr);
        if (meetSize) {
          PetscInt f;

          for (f = 0; f < numFaceCases; ++f) {
            if (numFaceVertices[f] == meetSize) {
              found = PETSC_TRUE;
              break;
            }
          }
        }
        ierr = DMPlexRestoreMeet(dm, 2, cellPair, &meetSize, &meet);CHKERRQ(ierr);
      }
      if (found) ++off[cell-cStart+1];
    }
  }
  /* Prefix sum */
  for (cell = 1; cell <= numCells; ++cell) off[cell] += off[cell-1];

  if (adjacency) {
    ierr = PetscMalloc1(off[numCells], &adj);CHKERRQ(ierr);
    /* Get neighboring cells */
    for (cell = cStart; cell < cEnd; ++cell) {
      PetscInt numNeighbors = PETSC_DETERMINE, n;
      PetscInt cellOffset   = 0;

      ierr = DMPlexGetAdjacency_Internal(dm, cell, PETSC_TRUE, PETSC_FALSE, &numNeighbors, &neighborCells);CHKERRQ(ierr);
      /* Get meet with each cell, and check with recognizer (could optimize to check each pair only once) */
      for (n = 0; n < numNeighbors; ++n) {
        PetscInt        cellPair[2];
        PetscBool       found    = faceDepth > 1 ? PETSC_TRUE : PETSC_FALSE;
        PetscInt        meetSize = 0;
        const PetscInt *meet    = NULL;

        cellPair[0] = cell; cellPair[1] = neighborCells[n];
        if (cellPair[0] == cellPair[1]) continue;
        if (!found) {
          ierr = DMPlexGetMeet(dm, 2, cellPair, &meetSize, &meet);CHKERRQ(ierr);
          if (meetSize) {
            PetscInt f;

            for (f = 0; f < numFaceCases; ++f) {
              if (numFaceVertices[f] == meetSize) {
                found = PETSC_TRUE;
                break;
              }
            }
          }
          ierr = DMPlexRestoreMeet(dm, 2, cellPair, &meetSize, &meet);CHKERRQ(ierr);
        }
        if (found) {
          adj[off[cell-cStart]+cellOffset] = neighborCells[n];
          ++cellOffset;
        }
      }
    }
  }
  ierr = PetscFree(neighborCells);CHKERRQ(ierr);
  if (numVertices) *numVertices = numCells;
  if (offsets)   *offsets   = off;
  if (adjacency) *adjacency = adj;
  PetscFunctionReturn(0);
}

#if defined(PETSC_HAVE_CHACO)
#if defined(PETSC_HAVE_UNISTD_H)
#include <unistd.h>
#endif
/* Chaco does not have an include file */
PETSC_EXTERN int interface(int nvtxs, int *start, int *adjacency, int *vwgts,
                       float *ewgts, float *x, float *y, float *z, char *outassignname,
                       char *outfilename, short *assignment, int architecture, int ndims_tot,
                       int mesh_dims[3], double *goal, int global_method, int local_method,
                       int rqi_flag, int vmax, int ndims, double eigtol, long seed);

extern int FREE_GRAPH;

#undef __FUNCT__
#define __FUNCT__ "DMPlexPartition_Chaco"
PetscErrorCode DMPlexPartition_Chaco(DM dm, PetscInt numVertices, PetscInt start[], PetscInt adjacency[], PetscSection *partSection, IS *partition)
{
  enum {DEFAULT_METHOD = 1, INERTIAL_METHOD = 3};
  MPI_Comm       comm;
  int            nvtxs          = numVertices; /* number of vertices in full graph */
  int           *vwgts          = NULL;   /* weights for all vertices */
  float         *ewgts          = NULL;   /* weights for all edges */
  float         *x              = NULL, *y = NULL, *z = NULL; /* coordinates for inertial method */
  char          *outassignname  = NULL;   /*  name of assignment output file */
  char          *outfilename    = NULL;   /* output file name */
  int            architecture   = 1;      /* 0 => hypercube, d => d-dimensional mesh */
  int            ndims_tot      = 0;      /* total number of cube dimensions to divide */
  int            mesh_dims[3];            /* dimensions of mesh of processors */
  double        *goal          = NULL;    /* desired set sizes for each set */
  int            global_method = 1;       /* global partitioning algorithm */
  int            local_method  = 1;       /* local partitioning algorithm */
  int            rqi_flag      = 0;       /* should I use RQI/Symmlq eigensolver? */
  int            vmax          = 200;     /* how many vertices to coarsen down to? */
  int            ndims         = 1;       /* number of eigenvectors (2^d sets) */
  double         eigtol        = 0.001;   /* tolerance on eigenvectors */
  long           seed          = 123636512; /* for random graph mutations */
  short int     *assignment;              /* Output partition */
  int            fd_stdout, fd_pipe[2];
  PetscInt      *points;
  PetscMPIInt    commSize;
  int            i, v, p;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectGetComm((PetscObject)dm,&comm);CHKERRQ(ierr);
  ierr = MPI_Comm_size(comm, &commSize);CHKERRQ(ierr);
  if (!numVertices) {
    ierr = PetscSectionCreate(comm, partSection);CHKERRQ(ierr);
    ierr = PetscSectionSetChart(*partSection, 0, commSize);CHKERRQ(ierr);
    ierr = PetscSectionSetUp(*partSection);CHKERRQ(ierr);
    ierr = ISCreateGeneral(comm, 0, NULL, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
    PetscFunctionReturn(0);
  }
  FREE_GRAPH = 0;                         /* Do not let Chaco free my memory */
  for (i = 0; i < start[numVertices]; ++i) ++adjacency[i];

  if (global_method == INERTIAL_METHOD) {
    /* manager.createCellCoordinates(nvtxs, &x, &y, &z); */
    SETERRQ(comm, PETSC_ERR_SUP, "Inertial partitioning not yet supported");
  }
  mesh_dims[0] = commSize;
  mesh_dims[1] = 1;
  mesh_dims[2] = 1;
  ierr = PetscMalloc1(nvtxs, &assignment);CHKERRQ(ierr);
  /* Chaco outputs to stdout. We redirect this to a buffer. */
  /* TODO: check error codes for UNIX calls */
#if defined(PETSC_HAVE_UNISTD_H)
  {
    int piperet;
    piperet = pipe(fd_pipe);
    if (piperet) SETERRQ(comm,PETSC_ERR_SYS,"Could not create pipe");
    fd_stdout = dup(1);
    close(1);
    dup2(fd_pipe[1], 1);
  }
#endif
  ierr = interface(nvtxs, (int*) start, (int*) adjacency, vwgts, ewgts, x, y, z, outassignname, outfilename,
                   assignment, architecture, ndims_tot, mesh_dims, goal, global_method, local_method, rqi_flag,
                   vmax, ndims, eigtol, seed);
#if defined(PETSC_HAVE_UNISTD_H)
  {
    char msgLog[10000];
    int  count;

    fflush(stdout);
    count = read(fd_pipe[0], msgLog, (10000-1)*sizeof(char));
    if (count < 0) count = 0;
    msgLog[count] = 0;
    close(1);
    dup2(fd_stdout, 1);
    close(fd_stdout);
    close(fd_pipe[0]);
    close(fd_pipe[1]);
    if (ierr) SETERRQ1(comm, PETSC_ERR_LIB, "Error in Chaco library: %s", msgLog);
  }
#endif
  /* Convert to PetscSection+IS */
  ierr = PetscSectionCreate(comm, partSection);CHKERRQ(ierr);
  ierr = PetscSectionSetChart(*partSection, 0, commSize);CHKERRQ(ierr);
  for (v = 0; v < nvtxs; ++v) {
    ierr = PetscSectionAddDof(*partSection, assignment[v], 1);CHKERRQ(ierr);
  }
  ierr = PetscSectionSetUp(*partSection);CHKERRQ(ierr);
  ierr = PetscMalloc1(nvtxs, &points);CHKERRQ(ierr);
  for (p = 0, i = 0; p < commSize; ++p) {
    for (v = 0; v < nvtxs; ++v) {
      if (assignment[v] == p) points[i++] = v;
    }
  }
  if (i != nvtxs) SETERRQ2(comm, PETSC_ERR_PLIB, "Number of points %D should be %D", i, nvtxs);
  ierr = ISCreateGeneral(comm, nvtxs, points, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
  if (global_method == INERTIAL_METHOD) {
    /* manager.destroyCellCoordinates(nvtxs, &x, &y, &z); */
  }
  ierr = PetscFree(assignment);CHKERRQ(ierr);
  for (i = 0; i < start[numVertices]; ++i) --adjacency[i];
  PetscFunctionReturn(0);
}
#endif

#if defined(PETSC_HAVE_PARMETIS)
#include <parmetis.h>

#undef __FUNCT__
#define __FUNCT__ "DMPlexPartition_ParMetis"
PetscErrorCode DMPlexPartition_ParMetis(DM dm, PetscInt numVertices, PetscInt start[], PetscInt adjacency[], PetscSection *partSection, IS *partition)
{
  MPI_Comm       comm;
  PetscInt       nvtxs      = numVertices; /* The number of vertices in full graph */
  PetscInt      *vtxdist;                  /* Distribution of vertices across processes */
  PetscInt      *xadj       = start;       /* Start of edge list for each vertex */
  PetscInt      *adjncy     = adjacency;   /* Edge lists for all vertices */
  PetscInt      *vwgt       = NULL;        /* Vertex weights */
  PetscInt      *adjwgt     = NULL;        /* Edge weights */
  PetscInt       wgtflag    = 0;           /* Indicates which weights are present */
  PetscInt       numflag    = 0;           /* Indicates initial offset (0 or 1) */
  PetscInt       ncon       = 1;           /* The number of weights per vertex */
  PetscInt       nparts;                   /* The number of partitions */
  PetscReal     *tpwgts;                   /* The fraction of vertex weights assigned to each partition */
  PetscReal     *ubvec;                    /* The balance intolerance for vertex weights */
  PetscInt       options[5];               /* Options */
  /* Outputs */
  PetscInt       edgeCut;                  /* The number of edges cut by the partition */
  PetscInt      *assignment, *points;
  PetscMPIInt    commSize, rank, p, v, i;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectGetComm((PetscObject) dm, &comm);CHKERRQ(ierr);
  ierr = MPI_Comm_size(comm, &commSize);CHKERRQ(ierr);
  ierr = MPI_Comm_rank(comm, &rank);CHKERRQ(ierr);
  nparts = commSize;
  options[0] = 0; /* Use all defaults */
  /* Calculate vertex distribution */
  ierr = PetscMalloc4(nparts+1,&vtxdist,nparts*ncon,&tpwgts,ncon,&ubvec,nvtxs,&assignment);CHKERRQ(ierr);
  vtxdist[0] = 0;
  ierr = MPI_Allgather(&nvtxs, 1, MPIU_INT, &vtxdist[1], 1, MPIU_INT, comm);CHKERRQ(ierr);
  for (p = 2; p <= nparts; ++p) {
    vtxdist[p] += vtxdist[p-1];
  }
  /* Calculate weights */
  for (p = 0; p < nparts; ++p) {
    tpwgts[p] = 1.0/nparts;
  }
  ubvec[0] = 1.05;

  if (nparts == 1) {
    ierr = PetscMemzero(assignment, nvtxs * sizeof(PetscInt));
  } else {
    if (vtxdist[1] == vtxdist[nparts]) {
      if (!rank) {
        PetscStackPush("METIS_PartGraphKway");
        ierr = METIS_PartGraphKway(&nvtxs, &ncon, xadj, adjncy, vwgt, NULL, adjwgt, &nparts, tpwgts, ubvec, NULL, &edgeCut, assignment);
        PetscStackPop;
        if (ierr != METIS_OK) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_LIB, "Error in METIS_PartGraphKway()");
      }
    } else {
      PetscStackPush("ParMETIS_V3_PartKway");
      ierr = ParMETIS_V3_PartKway(vtxdist, xadj, adjncy, vwgt, adjwgt, &wgtflag, &numflag, &ncon, &nparts, tpwgts, ubvec, options, &edgeCut, assignment, &comm);
      PetscStackPop;
      if (ierr != METIS_OK) SETERRQ(PETSC_COMM_SELF, PETSC_ERR_LIB, "Error in ParMETIS_V3_PartKway()");
    }
  }
  /* Convert to PetscSection+IS */
  ierr = PetscSectionCreate(comm, partSection);CHKERRQ(ierr);
  ierr = PetscSectionSetChart(*partSection, 0, commSize);CHKERRQ(ierr);
  for (v = 0; v < nvtxs; ++v) {
    ierr = PetscSectionAddDof(*partSection, assignment[v], 1);CHKERRQ(ierr);
  }
  ierr = PetscSectionSetUp(*partSection);CHKERRQ(ierr);
  ierr = PetscMalloc1(nvtxs, &points);CHKERRQ(ierr);
  for (p = 0, i = 0; p < commSize; ++p) {
    for (v = 0; v < nvtxs; ++v) {
      if (assignment[v] == p) points[i++] = v;
    }
  }
  if (i != nvtxs) SETERRQ2(comm, PETSC_ERR_PLIB, "Number of points %D should be %D", i, nvtxs);
  ierr = ISCreateGeneral(comm, nvtxs, points, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
  ierr = PetscFree4(vtxdist,tpwgts,ubvec,assignment);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}
#endif

#undef __FUNCT__
#define __FUNCT__ "DMPlexEnlargePartition"
/* Expand the partition by BFS on the adjacency graph */
PetscErrorCode DMPlexEnlargePartition(DM dm, const PetscInt start[], const PetscInt adjacency[], PetscSection origPartSection, IS origPartition, PetscSection *partSection, IS *partition)
{
  PetscHashI      h;
  const PetscInt *points;
  PetscInt      **tmpPoints, *newPoints, totPoints = 0;
  PetscInt        pStart, pEnd, part, q;
  PetscBool       useCone;
  PetscErrorCode  ierr;

  PetscFunctionBegin;
  PetscHashICreate(h);
  ierr = PetscSectionCreate(PetscObjectComm((PetscObject)dm), partSection);CHKERRQ(ierr);
  ierr = PetscSectionGetChart(origPartSection, &pStart, &pEnd);CHKERRQ(ierr);
  ierr = PetscSectionSetChart(*partSection, pStart, pEnd);CHKERRQ(ierr);
  ierr = ISGetIndices(origPartition, &points);CHKERRQ(ierr);
  ierr = PetscMalloc1((pEnd - pStart), &tmpPoints);CHKERRQ(ierr);
  ierr = DMPlexGetAdjacencyUseCone(dm, &useCone);CHKERRQ(ierr);
  ierr = DMPlexSetAdjacencyUseCone(dm, PETSC_TRUE);CHKERRQ(ierr);
  for (part = pStart; part < pEnd; ++part) {
    PetscInt *adj = NULL;
    PetscInt  numPoints, nP, numNewPoints, off, p, n = 0;

    PetscHashIClear(h);
    ierr = PetscSectionGetDof(origPartSection, part, &numPoints);CHKERRQ(ierr);
    ierr = PetscSectionGetOffset(origPartSection, part, &off);CHKERRQ(ierr);
    /* Add all existing points to h */
    for (p = 0; p < numPoints; ++p) {
      const PetscInt point = points[off+p];
      PetscHashIAdd(h, point, 1);
    }
    PetscHashISize(h, nP);
    if (nP != numPoints) SETERRQ2(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_WRONG, "Invalid partition has %d points, but only %d were unique", numPoints, nP);
    /* Add all points in next BFS level */
    for (p = 0; p < numPoints; ++p) {
      const PetscInt point   = points[off+p];
      PetscInt       adjSize = PETSC_DETERMINE, a;

      ierr = DMPlexGetAdjacency(dm, point, &adjSize, &adj);CHKERRQ(ierr);
      for (a = 0; a < adjSize; ++a) PetscHashIAdd(h, adj[a], 1);
    }
    PetscHashISize(h, numNewPoints);
    ierr = PetscSectionSetDof(*partSection, part, numNewPoints);CHKERRQ(ierr);
    ierr = PetscMalloc1(numNewPoints, &tmpPoints[part]);CHKERRQ(ierr);
    ierr = PetscHashIGetKeys(h, &n, tmpPoints[part]);CHKERRQ(ierr);
    ierr = PetscFree(adj);CHKERRQ(ierr);
    totPoints += numNewPoints;
  }
  ierr = DMPlexSetAdjacencyUseCone(dm, useCone);CHKERRQ(ierr);
  ierr = ISRestoreIndices(origPartition, &points);CHKERRQ(ierr);
  PetscHashIDestroy(h);
  ierr = PetscSectionSetUp(*partSection);CHKERRQ(ierr);
  ierr = PetscMalloc1(totPoints, &newPoints);CHKERRQ(ierr);
  for (part = pStart, q = 0; part < pEnd; ++part) {
    PetscInt numPoints, p;

    ierr = PetscSectionGetDof(*partSection, part, &numPoints);CHKERRQ(ierr);
    for (p = 0; p < numPoints; ++p, ++q) newPoints[q] = tmpPoints[part][p];
    ierr = PetscFree(tmpPoints[part]);CHKERRQ(ierr);
  }
  ierr = PetscFree(tmpPoints);CHKERRQ(ierr);
  ierr = ISCreateGeneral(PetscObjectComm((PetscObject)dm), totPoints, newPoints, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMPlexCreatePartition"
/*
  DMPlexCreatePartition - Create a non-overlapping partition of the points at the given height

  Collective on DM

  Input Parameters:
  + dm - The DM
  . height - The height for points in the partition
  - enlarge - Expand each partition with neighbors

  Output Parameters:
  + partSection - The PetscSection giving the division of points by partition
  . partition - The list of points by partition
  . origPartSection - If enlarge is true, the PetscSection giving the division of points before enlarging by partition, otherwise NULL
  - origPartition - If enlarge is true, the list of points before enlarging by partition, otherwise NULL

  Level: developer

.seealso DMPlexDistribute()
*/
PetscErrorCode DMPlexCreatePartition(DM dm, const char name[], PetscInt height, PetscBool enlarge, PetscSection *partSection, IS *partition, PetscSection *origPartSection, IS *origPartition)
{
  char           partname[1024];
  PetscBool      isChaco = PETSC_FALSE, isMetis = PETSC_FALSE, flg;
  PetscMPIInt    size;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = MPI_Comm_size(PetscObjectComm((PetscObject)dm), &size);CHKERRQ(ierr);

  *origPartSection = NULL;
  *origPartition   = NULL;
  if (size == 1) {
    PetscInt *points;
    PetscInt  cStart, cEnd, c;

    ierr = DMPlexGetHeightStratum(dm, 0, &cStart, &cEnd);CHKERRQ(ierr);
    ierr = PetscSectionCreate(PetscObjectComm((PetscObject)dm), partSection);CHKERRQ(ierr);
    ierr = PetscSectionSetChart(*partSection, 0, size);CHKERRQ(ierr);
    ierr = PetscSectionSetDof(*partSection, 0, cEnd-cStart);CHKERRQ(ierr);
    ierr = PetscSectionSetUp(*partSection);CHKERRQ(ierr);
    ierr = PetscMalloc1((cEnd - cStart), &points);CHKERRQ(ierr);
    for (c = cStart; c < cEnd; ++c) points[c] = c;
    ierr = ISCreateGeneral(PetscObjectComm((PetscObject)dm), cEnd-cStart, points, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
    PetscFunctionReturn(0);
  }
  ierr = PetscOptionsGetString(((PetscObject) dm)->prefix, "-dm_plex_partitioner", partname, 1024, &flg);CHKERRQ(ierr);
  if (flg) name = partname;
  if (name) {
    ierr = PetscStrcmp(name, "chaco", &isChaco);CHKERRQ(ierr);
    ierr = PetscStrcmp(name, "metis", &isMetis);CHKERRQ(ierr);
  }
  if (height == 0) {
    PetscInt  numVertices;
    PetscInt *start     = NULL;
    PetscInt *adjacency = NULL;

    ierr = DMPlexCreateNeighborCSR(dm, 0, &numVertices, &start, &adjacency);CHKERRQ(ierr);
    if (!name || isChaco) {
#if defined(PETSC_HAVE_CHACO)
      ierr = DMPlexPartition_Chaco(dm, numVertices, start, adjacency, partSection, partition);CHKERRQ(ierr);
#else
      SETERRQ(PetscObjectComm((PetscObject) dm), PETSC_ERR_SUP, "Mesh partitioning needs external package support.\nPlease reconfigure with --download-chaco.");
#endif
    } else if (isMetis) {
#if defined(PETSC_HAVE_PARMETIS)
      ierr = DMPlexPartition_ParMetis(dm, numVertices, start, adjacency, partSection, partition);CHKERRQ(ierr);
#endif
    } else SETERRQ1(PetscObjectComm((PetscObject) dm), PETSC_ERR_SUP, "Unknown mesh partitioning package %s", name);
    if (enlarge) {
      *origPartSection = *partSection;
      *origPartition   = *partition;

      ierr = DMPlexEnlargePartition(dm, start, adjacency, *origPartSection, *origPartition, partSection, partition);CHKERRQ(ierr);
    }
    ierr = PetscFree(start);CHKERRQ(ierr);
    ierr = PetscFree(adjacency);CHKERRQ(ierr);
# if 0
  } else if (height == 1) {
    /* Build the dual graph for faces and partition the hypergraph */
    PetscInt numEdges;

    buildFaceCSRV(mesh, mesh->getFactory()->getNumbering(mesh, mesh->depth()-1), &numEdges, &start, &adjacency, GraphPartitioner::zeroBase());
    GraphPartitioner().partition(numEdges, start, adjacency, partition, manager);
    destroyCSR(numEdges, start, adjacency);
#endif
  } else SETERRQ1(PetscObjectComm((PetscObject)dm), PETSC_ERR_ARG_OUTOFRANGE, "Invalid partition height %D", height);
  PetscFunctionReturn(0);
}

#undef __FUNCT__
#define __FUNCT__ "DMPlexCreatePartitionClosure"
PetscErrorCode DMPlexCreatePartitionClosure(DM dm, PetscSection pointSection, IS pointPartition, PetscSection *section, IS *partition)
{
  /* const PetscInt  height = 0; */
  const PetscInt *partArray;
  PetscInt       *allPoints, *packPoints;
  PetscInt        rStart, rEnd, rank, pStart, pEnd, newSize;
  PetscErrorCode  ierr;
  PetscBT         bt;
  PetscSegBuffer  segpack,segpart;

  PetscFunctionBegin;
  ierr = PetscSectionGetChart(pointSection, &rStart, &rEnd);CHKERRQ(ierr);
  ierr = ISGetIndices(pointPartition, &partArray);CHKERRQ(ierr);
  ierr = PetscSectionCreate(PetscObjectComm((PetscObject)dm), section);CHKERRQ(ierr);
  ierr = PetscSectionSetChart(*section, rStart, rEnd);CHKERRQ(ierr);
  ierr = DMPlexGetChart(dm,&pStart,&pEnd);CHKERRQ(ierr);
  ierr = PetscBTCreate(pEnd-pStart,&bt);CHKERRQ(ierr);
  ierr = PetscSegBufferCreate(sizeof(PetscInt),1000,&segpack);CHKERRQ(ierr);
  ierr = PetscSegBufferCreate(sizeof(PetscInt),1000,&segpart);CHKERRQ(ierr);
  for (rank = rStart; rank < rEnd; ++rank) {
    PetscInt partSize = 0, numPoints, offset, p, *PETSC_RESTRICT placePoints;

    ierr = PetscSectionGetDof(pointSection, rank, &numPoints);CHKERRQ(ierr);
    ierr = PetscSectionGetOffset(pointSection, rank, &offset);CHKERRQ(ierr);
    for (p = 0; p < numPoints; ++p) {
      PetscInt  point   = partArray[offset+p], closureSize, c;
      PetscInt *closure = NULL;

      /* TODO Include support for height > 0 case */
      ierr = DMPlexGetTransitiveClosure(dm, point, PETSC_TRUE, &closureSize, &closure);CHKERRQ(ierr);
      for (c=0; c<closureSize; c++) {
        PetscInt cpoint = closure[c*2];
        if (!PetscBTLookupSet(bt,cpoint-pStart)) {
          PetscInt *PETSC_RESTRICT pt;
          partSize++;
          ierr = PetscSegBufferGetInts(segpart,1,&pt);CHKERRQ(ierr);
          *pt = cpoint;
        }
      }
      ierr = DMPlexRestoreTransitiveClosure(dm, point, PETSC_TRUE, &closureSize, &closure);CHKERRQ(ierr);
    }
    ierr = PetscSectionSetDof(*section, rank, partSize);CHKERRQ(ierr);
    ierr = PetscSegBufferGetInts(segpack,partSize,&placePoints);CHKERRQ(ierr);
    ierr = PetscSegBufferExtractTo(segpart,placePoints);CHKERRQ(ierr);
    ierr = PetscSortInt(partSize,placePoints);CHKERRQ(ierr);
    for (p=0; p<partSize; p++) {ierr = PetscBTClear(bt,placePoints[p]-pStart);CHKERRQ(ierr);}
  }
  ierr = PetscBTDestroy(&bt);CHKERRQ(ierr);
  ierr = PetscSegBufferDestroy(&segpart);CHKERRQ(ierr);

  ierr = PetscSectionSetUp(*section);CHKERRQ(ierr);
  ierr = PetscSectionGetStorageSize(*section, &newSize);CHKERRQ(ierr);
  ierr = PetscMalloc1(newSize, &allPoints);CHKERRQ(ierr);

  ierr = PetscSegBufferExtractInPlace(segpack,&packPoints);CHKERRQ(ierr);
  for (rank = rStart; rank < rEnd; ++rank) {
    PetscInt numPoints, offset;

    ierr = PetscSectionGetDof(*section, rank, &numPoints);CHKERRQ(ierr);
    ierr = PetscSectionGetOffset(*section, rank, &offset);CHKERRQ(ierr);
    ierr = PetscMemcpy(&allPoints[offset], packPoints, numPoints * sizeof(PetscInt));CHKERRQ(ierr);
    packPoints += numPoints;
  }

  ierr = PetscSegBufferDestroy(&segpack);CHKERRQ(ierr);
  ierr = ISRestoreIndices(pointPartition, &partArray);CHKERRQ(ierr);
  ierr = ISCreateGeneral(PetscObjectComm((PetscObject)dm), newSize, allPoints, PETSC_OWN_POINTER, partition);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}