C++ ISGetLocalSize函数代码示例

/*@
   ISConcatenate - Forms a new IS by locally concatenating the indices from an IS list without reordering.
 

   Collective on comm.

   Input Parameter:
+  comm    - communicator of the concatenated IS.
.  len     - size of islist array (nonnegative)
-  islist  - array of index sets



   Output Parameters:
.  isout   - The concatenated index set; empty, if len == 0.

   Notes: The semantics of calling this on comm imply that the comms of the members if islist also contain this rank.

   Level: intermediate

.seealso: ISDifference(), ISSum(), ISExpand()

   Concepts: index sets^concatenation
   Concepts: IS^concatenation

@*/
PetscErrorCode ISConcatenate(MPI_Comm comm, PetscInt len, const IS islist[], IS *isout)
{
  PetscErrorCode ierr;
  PetscInt i,n,N;
  const PetscInt *iidx;
  PetscInt *idx;

  PetscFunctionBegin;
  PetscValidPointer(islist,2);
#if defined(PETSC_USE_DEBUG)
  for(i = 0; i < len; ++i) {
    PetscValidHeaderSpecific(islist[i], IS_CLASSID, 1);
  }
#endif
  PetscValidPointer(isout, 5);
  if(!len) {
    ierr = ISCreateStride(comm, 0,0,0, isout); CHKERRQ(ierr);
    PetscFunctionReturn(0);
  }
  if(len < 0) SETERRQ1(PETSC_COMM_SELF, PETSC_ERR_ARG_WRONG, "Negative array length: %D", len);
  N = 0; 
  for(i = 0; i < len; ++i) {
    ierr = ISGetLocalSize(islist[i], &n); CHKERRQ(ierr);
    N += n;
  }
  ierr = PetscMalloc(sizeof(PetscInt)*N, &idx); CHKERRQ(ierr);
  N = 0; 
  for(i = 0; i < len; ++i) {
    ierr = ISGetLocalSize(islist[i], &n); CHKERRQ(ierr);
    ierr = ISGetIndices(islist[i], &iidx); CHKERRQ(ierr);
    ierr = PetscMemcpy(idx+N,iidx, sizeof(PetscInt)*n); CHKERRQ(ierr);
    N += n;
  }
  ierr = ISCreateGeneral(comm, N, idx, PETSC_OWN_POINTER, isout); CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*@
   AOApplicationToPetscIS - Maps an index set in the application-defined
   ordering to the PETSc ordering.

   Collective on AO and IS

   Input Parameters:
+  ao - the application ordering context
-  is - the index set; this is replaced with its mapped values

   Output Parameter:
.  is - the mapped index set

   Level: beginner

   Note:
   The index set cannot be of type stride or block

   Any integers in ia[] that are negative are left unchanged. This
   allows one to convert, for example, neighbor lists that use negative
   entries to indicate nonexistent neighbors due to boundary conditions, etc.

.keywords: application ordering, mapping

.seealso: AOCreateBasic(), AOView(), AOPetscToApplication(),
          AOPetscToApplicationIS(), AOApplicationToPetsc()
@*/
PetscErrorCode  AOApplicationToPetscIS(AO ao,IS is)
{
  PetscErrorCode ierr;
  PetscInt       n,*ia;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(ao,AO_CLASSID,1);
  PetscValidHeaderSpecific(is,IS_CLASSID,2);
  ierr = ISToGeneral(is);CHKERRQ(ierr);
  /* we cheat because we know the is is general and that we can change the indices */
  ierr = ISGetIndices(is,(const PetscInt**)&ia);CHKERRQ(ierr);
  ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
  ierr = (*ao->ops->applicationtopetsc)(ao,n,ia);CHKERRQ(ierr);
  ierr = ISRestoreIndices(is,(const PetscInt**)&ia);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode ISView_Block(IS is, PetscViewer viewer)
{
  IS_Block       *sub = (IS_Block*)is->data;
  PetscErrorCode ierr;
  PetscInt       i,bs,n,*idx = sub->idx;
  PetscBool      iascii;

  PetscFunctionBegin;
  ierr = PetscLayoutGetBlockSize(is->map, &bs);CHKERRQ(ierr);
  ierr = PetscLayoutGetLocalSize(is->map, &n);CHKERRQ(ierr);
  n   /= bs;
  ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
  if (iascii) {
    PetscViewerFormat fmt;

    ierr = PetscViewerGetFormat(viewer,&fmt);CHKERRQ(ierr);
    if (fmt == PETSC_VIEWER_ASCII_MATLAB) {
      IS             ist;
      const char     *name;
      const PetscInt *idx;
      PetscInt       n;

      ierr = PetscObjectGetName((PetscObject)is,&name);CHKERRQ(ierr);
      ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
      ierr = ISGetIndices(is,&idx);CHKERRQ(ierr);
      ierr = ISCreateGeneral(PetscObjectComm((PetscObject)is),n,idx,PETSC_USE_POINTER,&ist);CHKERRQ(ierr);
      ierr = PetscObjectSetName((PetscObject)ist,name);CHKERRQ(ierr);
      ierr = ISView(ist,viewer);CHKERRQ(ierr);
      ierr = ISDestroy(&ist);CHKERRQ(ierr);
      ierr = ISRestoreIndices(is,&idx);CHKERRQ(ierr);
    } else {
      ierr = PetscViewerASCIIPushSynchronized(viewer);CHKERRQ(ierr);
      if (is->isperm) {
        ierr = PetscViewerASCIISynchronizedPrintf(viewer,"Block Index set is permutation\n");CHKERRQ(ierr);
      }
      ierr = PetscViewerASCIISynchronizedPrintf(viewer,"Block size %D\n",bs);CHKERRQ(ierr);
      ierr = PetscViewerASCIISynchronizedPrintf(viewer,"Number of block indices in set %D\n",n);CHKERRQ(ierr);
      ierr = PetscViewerASCIISynchronizedPrintf(viewer,"The first indices of each block are\n");CHKERRQ(ierr);
      for (i=0; i<n; i++) {
        ierr = PetscViewerASCIISynchronizedPrintf(viewer,"Block %D Index %D\n",i,idx[i]);CHKERRQ(ierr);
      }
      ierr = PetscViewerFlush(viewer);CHKERRQ(ierr);
      ierr = PetscViewerASCIIPopSynchronized(viewer);CHKERRQ(ierr);
    }
  }
  PetscFunctionReturn(0);
}

/*@
    ISPartitioningToNumbering - Takes an ISPartitioning and on each processor
    generates an IS that contains a new global node number for each index based
    on the partitioing.

    Collective on IS

    Input Parameters
.   partitioning - a partitioning as generated by MatPartitioningApply()

    Output Parameter:
.   is - on each processor the index set that defines the global numbers
         (in the new numbering) for all the nodes currently (before the partitioning)
         on that processor

   Level: advanced

.seealso: MatPartitioningCreate(), AOCreateBasic(), ISPartitioningCount()

@*/
PetscErrorCode  ISPartitioningToNumbering(IS part,IS *is)
{
  MPI_Comm       comm;
  PetscInt       i,np,npt,n,*starts = NULL,*sums = NULL,*lsizes = NULL,*newi = NULL;
  const PetscInt *indices = NULL;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = PetscObjectGetComm((PetscObject)part,&comm);CHKERRQ(ierr);

  /* count the number of partitions, i.e., virtual processors */
  ierr = ISGetLocalSize(part,&n);CHKERRQ(ierr);
  ierr = ISGetIndices(part,&indices);CHKERRQ(ierr);
  np   = 0;
  for (i=0; i<n; i++) np = PetscMax(np,indices[i]);
  ierr = MPI_Allreduce(&np,&npt,1,MPIU_INT,MPI_MAX,comm);CHKERRQ(ierr);
  np   = npt+1; /* so that it looks like a MPI_Comm_size output */

  /*
        lsizes - number of elements of each partition on this particular processor
        sums - total number of "previous" nodes for any particular partition
        starts - global number of first element in each partition on this processor
  */
  ierr = PetscMalloc3(np,&lsizes,np,&starts,np,&sums);CHKERRQ(ierr);
  ierr = PetscMemzero(lsizes,np*sizeof(PetscInt));CHKERRQ(ierr);
  for (i=0; i<n; i++) lsizes[indices[i]]++;
  ierr = MPI_Allreduce(lsizes,sums,np,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr);
  ierr = MPI_Scan(lsizes,starts,np,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr);
  for (i=0; i<np; i++) starts[i] -= lsizes[i];
  for (i=1; i<np; i++) {
    sums[i]   += sums[i-1];
    starts[i] += sums[i-1];
  }

  /*
      For each local index give it the new global number
  */
  ierr = PetscMalloc1(n,&newi);CHKERRQ(ierr);
  for (i=0; i<n; i++) newi[i] = starts[indices[i]]++;
  ierr = PetscFree3(lsizes,starts,sums);CHKERRQ(ierr);

  ierr = ISRestoreIndices(part,&indices);CHKERRQ(ierr);
  ierr = ISCreateGeneral(comm,n,newi,PETSC_OWN_POINTER,is);CHKERRQ(ierr);
  ierr = ISSetPermutation(*is);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/*@
  VecISAXPY - Adds a reduced vector to the appropriate elements of a full-space vector. 
                  vfull[is[i]] += alpha*vreduced[i]

  Input Parameters:
+ vfull - the full-space vector
. vreduced - the reduced-space vector
- is - the index set for the reduced space

  Output Parameters:
. vfull - the sum of the full-space vector and reduced-space vector

  Level: advanced

.seealso:  VecAXPY()
@*/
PetscErrorCode VecISAXPY(Vec vfull, IS is, PetscScalar alpha,Vec vreduced)
{
  PetscInt       nfull,nreduced;
  MPI_Comm       comm;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(vfull,VEC_CLASSID,1);
  PetscValidHeaderSpecific(vreduced,VEC_CLASSID,2);
  PetscValidHeaderSpecific(is,IS_CLASSID,3);
  ierr = VecGetSize(vfull,&nfull);CHKERRQ(ierr);
  ierr = VecGetSize(vreduced,&nreduced);CHKERRQ(ierr);

  if (nfull == nreduced) { /* Also takes care of masked vectors */
    ierr = VecAXPY(vfull,alpha,vreduced);CHKERRQ(ierr);
  } else {
    PetscScalar      *y;
    const PetscScalar *x;
    PetscInt          i,n,m,rstart;
    const PetscInt    *id;

    ierr = PetscObjectGetComm((PetscObject)vfull,&comm);CHKERRQ(ierr);
    ierr = VecGetArray(vfull,&y);CHKERRQ(ierr);
    ierr = VecGetArrayRead(vreduced,&x);CHKERRQ(ierr);
    ierr = ISGetIndices(is,&id);CHKERRQ(ierr);
    ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
    ierr = VecGetLocalSize(vreduced,&m);CHKERRQ(ierr);
    if (m != n) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"IS local length not equal to Vec local length");
    ierr = VecGetOwnershipRange(vfull,&rstart,NULL);CHKERRQ(ierr);
    y -= rstart;
    if (alpha == 1.0) {
      for (i=0; i<n; i++) {
        y[id[i]] += x[i];
      }
    } else {
      for (i=0; i<n; i++) {
        y[id[i]] += alpha*x[i];
      }
    }
    y += rstart;
    ierr = ISRestoreIndices(is,&id);CHKERRQ(ierr);
    ierr = VecRestoreArray(vfull,&y);CHKERRQ(ierr);
    ierr = VecRestoreArrayRead(vreduced,&x);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode ISGetBlockGlobalIS(IS is, Vec vec, PetscInt bs, IS *isBlockGlobal)
{
  const PetscInt *idxin;
  PetscInt       *idxout, i, n, rstart;
  PetscLayout    map;
  PetscErrorCode ierr;

  PetscFunctionBegin;

  ierr = VecGetLayout(vec,&map);CHKERRQ(ierr);
  rstart = map->rstart / bs;
  ierr = ISGetLocalSize(is, &n);CHKERRQ(ierr);
  ierr = PetscMalloc1(n, &idxout);CHKERRQ(ierr);
  ierr = ISGetIndices(is, &idxin);CHKERRQ(ierr);
  for (i = 0; i < n; i++) idxout[i] = rstart + idxin[i];
  ierr = ISRestoreIndices(is, &idxin);CHKERRQ(ierr);
  ierr = ISCreateBlock(PetscObjectComm((PetscObject)vec),bs,n,idxout,PETSC_OWN_POINTER,isBlockGlobal);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode ISGatherTotal_Private(IS is)
{
    PetscErrorCode ierr;
    PetscInt       i,n,N;
    const PetscInt *lindices;
    MPI_Comm       comm;
    PetscMPIInt    rank,size,*sizes = NULL,*offsets = NULL,nn;

    PetscFunctionBegin;
    PetscValidHeaderSpecific(is,IS_CLASSID,1);

    ierr = PetscObjectGetComm((PetscObject)is,&comm);
    CHKERRQ(ierr);
    ierr = MPI_Comm_size(comm,&size);
    CHKERRQ(ierr);
    ierr = MPI_Comm_rank(comm,&rank);
    CHKERRQ(ierr);
    ierr = ISGetLocalSize(is,&n);
    CHKERRQ(ierr);
    ierr = PetscMalloc2(size,&sizes,size,&offsets);
    CHKERRQ(ierr);

    ierr = PetscMPIIntCast(n,&nn);
    CHKERRQ(ierr);
    ierr = MPI_Allgather(&nn,1,MPI_INT,sizes,1,MPI_INT,comm);
    CHKERRQ(ierr);
    offsets[0] = 0;
    for (i=1; i<size; ++i) offsets[i] = offsets[i-1] + sizes[i-1];
    N = offsets[size-1] + sizes[size-1];

    ierr = PetscMalloc1(N,&(is->total));
    CHKERRQ(ierr);
    ierr = ISGetIndices(is,&lindices);
    CHKERRQ(ierr);
    ierr = MPI_Allgatherv((void*)lindices,nn,MPIU_INT,is->total,sizes,offsets,MPIU_INT,comm);
    CHKERRQ(ierr);
    ierr = ISRestoreIndices(is,&lindices);
    CHKERRQ(ierr);
    is->local_offset = offsets[rank];
    ierr = PetscFree2(sizes,offsets);
    CHKERRQ(ierr);
    PetscFunctionReturn(0);
}

/*@
    ISPartitioningCount - Takes a ISPartitioning and determines the number of
    resulting elements on each (partition) process

    Collective on IS

    Input Parameters:
+   partitioning - a partitioning as generated by MatPartitioningApply()
-   len - length of the array count, this is the total number of partitions

    Output Parameter:
.   count - array of length size, to contain the number of elements assigned
        to each partition, where size is the number of partitions generated
         (see notes below).

   Level: advanced

    Notes:
        By default the number of partitions generated (and thus the length
        of count) is the size of the communicator associated with IS,
        but it can be set by MatPartitioningSetNParts. The resulting array
        of lengths can for instance serve as input of PCBJacobiSetTotalBlocks.


.seealso: MatPartitioningCreate(), AOCreateBasic(), ISPartitioningToNumbering(),
        MatPartitioningSetNParts(), MatPartitioningApply()

@*/
PetscErrorCode  ISPartitioningCount(IS part,PetscInt len,PetscInt count[])
{
  MPI_Comm       comm;
  PetscInt       i,n,*lsizes;
  const PetscInt *indices;
  PetscErrorCode ierr;
  PetscMPIInt    npp;

  PetscFunctionBegin;
  ierr = PetscObjectGetComm((PetscObject)part,&comm);CHKERRQ(ierr);
  if (len == PETSC_DEFAULT) {
    PetscMPIInt size;
    ierr = MPI_Comm_size(comm,&size);CHKERRQ(ierr);
    len  = (PetscInt) size;
  }

  /* count the number of partitions */
  ierr = ISGetLocalSize(part,&n);CHKERRQ(ierr);
  ierr = ISGetIndices(part,&indices);CHKERRQ(ierr);
#if defined(PETSC_USE_DEBUG)
  {
    PetscInt np = 0,npt;
    for (i=0; i<n; i++) np = PetscMax(np,indices[i]);
    ierr = MPI_Allreduce(&np,&npt,1,MPIU_INT,MPI_MAX,comm);CHKERRQ(ierr);
    np   = npt+1; /* so that it looks like a MPI_Comm_size output */
    if (np > len) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Length of count array %D is less than number of partitions %D",len,np);
  }
#endif

  /*
        lsizes - number of elements of each partition on this particular processor
        sums - total number of "previous" nodes for any particular partition
        starts - global number of first element in each partition on this processor
  */
  ierr = PetscMalloc(len*sizeof(PetscInt),&lsizes);CHKERRQ(ierr);
  ierr = PetscMemzero(lsizes,len*sizeof(PetscInt));CHKERRQ(ierr);
  for (i=0; i<n; i++) lsizes[indices[i]]++;
  ierr = ISRestoreIndices(part,&indices);CHKERRQ(ierr);
  ierr = PetscMPIIntCast(len,&npp);CHKERRQ(ierr);
  ierr = MPI_Allreduce(lsizes,count,npp,MPIU_INT,MPI_SUM,comm);CHKERRQ(ierr);
  ierr = PetscFree(lsizes);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode VecSetUp_NestIS_Private(Vec V,PetscInt nb,IS is[])
{
  Vec_Nest       *ctx = (Vec_Nest*)V->data;
  PetscInt       i,offset,m,n,M,N;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  if (is) {                     /* Do some consistency checks and reference the is */
    offset = V->map->rstart;
    for (i=0; i<ctx->nb; i++) {
      ierr = ISGetSize(is[i],&M);CHKERRQ(ierr);
      ierr = VecGetSize(ctx->v[i],&N);CHKERRQ(ierr);
      if (M != N) SETERRQ3(PetscObjectComm((PetscObject)V),PETSC_ERR_ARG_INCOMP,"In slot %D, IS of size %D is not compatible with Vec of size %D",i,M,N);
      ierr = ISGetLocalSize(is[i],&m);CHKERRQ(ierr);
      ierr = VecGetLocalSize(ctx->v[i],&n);CHKERRQ(ierr);
      if (m != n) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"In slot %D, IS of local size %D is not compatible with Vec of local size %D",i,m,n);
#if defined(PETSC_USE_DEBUG)
      {                         /* This test can be expensive */
        PetscInt  start;
        PetscBool contiguous;
        ierr = ISContiguousLocal(is[i],offset,offset+n,&start,&contiguous);CHKERRQ(ierr);
        if (!contiguous) SETERRQ1(PetscObjectComm((PetscObject)V),PETSC_ERR_SUP,"Index set %D is not contiguous with layout of matching vector",i);
        if (start != 0) SETERRQ1(PetscObjectComm((PetscObject)V),PETSC_ERR_SUP,"Index set %D introduces overlap or a hole",i);
      }
#endif
      ierr = PetscObjectReference((PetscObject)is[i]);CHKERRQ(ierr);
      ctx->is[i] = is[i];
      offset += n;
    }
  } else {                      /* Create a contiguous ISStride for each entry */
    offset = V->map->rstart;
    for (i=0; i<ctx->nb; i++) {
      PetscInt bs;
      ierr = VecGetLocalSize(ctx->v[i],&n);CHKERRQ(ierr);
      ierr = VecGetBlockSize(ctx->v[i],&bs);CHKERRQ(ierr);
      ierr = ISCreateStride(((PetscObject)ctx->v[i])->comm,n,offset,1,&ctx->is[i]);CHKERRQ(ierr);
      ierr = ISSetBlockSize(ctx->is[i],bs);CHKERRQ(ierr);
      offset += n;
    }
  }
  PetscFunctionReturn(0);
}

int main(int argc,char **argv)
{
  PetscInt       i,n,start,stride;
  const PetscInt *ii;
  IS             is;
  PetscBool      flg;
  PetscErrorCode ierr;

  ierr = PetscInitialize(&argc,&argv,(char*)0,help);CHKERRQ(ierr);

  /*
     Test IS of size 0
  */
  ierr = ISCreateStride(PETSC_COMM_SELF,0,0,2,&is);CHKERRQ(ierr);
  ierr = ISGetSize(is,&n);CHKERRQ(ierr);
  if (n != 0) SETERRQ(PETSC_COMM_SELF,1,"ISCreateStride");
  ierr = ISStrideGetInfo(is,&start,&stride);CHKERRQ(ierr);
  if (start != 0) SETERRQ(PETSC_COMM_SELF,1,"ISStrideGetInfo");
  if (stride != 2) SETERRQ(PETSC_COMM_SELF,1,"ISStrideGetInfo");
  ierr = PetscObjectTypeCompare((PetscObject)is,ISSTRIDE,&flg);CHKERRQ(ierr);
  if (!flg) SETERRQ(PETSC_COMM_SELF,1,"ISStride");
  ierr = ISGetIndices(is,&ii);CHKERRQ(ierr);
  ierr = ISRestoreIndices(is,&ii);CHKERRQ(ierr);
  ierr = ISDestroy(&is);CHKERRQ(ierr);

  /*
     Test ISGetIndices()
  */
  ierr = ISCreateStride(PETSC_COMM_SELF,10000,-8,3,&is);CHKERRQ(ierr);
  ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
  ierr = ISGetIndices(is,&ii);CHKERRQ(ierr);
  for (i=0; i<10000; i++) {
    if (ii[i] != -8 + 3*i) SETERRQ(PETSC_COMM_SELF,1,"ISGetIndices");
  }
  ierr = ISRestoreIndices(is,&ii);CHKERRQ(ierr);
  ierr = ISDestroy(&is);CHKERRQ(ierr);

  ierr = PetscFinalize();
  return 0;
}

/*@
    ISComplement - Given an index set (IS) generates the complement index set. That is all
       all indices that are NOT in the given set.

    Collective on IS

    Input Parameter:
+   is - the index set
.   nmin - the first index desired in the local part of the complement
-   nmax - the largest index desired in the local part of the complement (note that all indices in is must be greater or equal to nmin and less than nmax)

    Output Parameter:
.   isout - the complement

    Notes:  The communicator for this new IS is the same as for the input IS

      For a parallel IS, this will generate the local part of the complement on each process

      To generate the entire complement (on each process) of a parallel IS, first call ISAllGather() and then
    call this routine.

    Level: intermediate

    Concepts: gather^index sets
    Concepts: index sets^gathering to all processors
    Concepts: IS^gathering to all processors

.seealso: ISCreateGeneral(), ISCreateStride(), ISCreateBlock(), ISAllGather()
@*/
PetscErrorCode  ISComplement(IS is,PetscInt nmin,PetscInt nmax,IS *isout)
{
  PetscErrorCode ierr;
  const PetscInt *indices;
  PetscInt       n,i,j,unique,cnt,*nindices;
  PetscBool      sorted;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(is,IS_CLASSID,1);
  PetscValidPointer(isout,3);
  if (nmin < 0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"nmin %D cannot be negative",nmin);
  if (nmin > nmax) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"nmin %D cannot be greater than nmax %D",nmin,nmax);
  ierr = ISSorted(is,&sorted);CHKERRQ(ierr);
  if (!sorted) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Index set must be sorted");

  ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
  ierr = ISGetIndices(is,&indices);CHKERRQ(ierr);
#if defined(PETSC_USE_DEBUG)
  for (i=0; i<n; i++) {
    if (indices[i] <  nmin) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Index %D's value %D is smaller than minimum given %D",i,indices[i],nmin);
    if (indices[i] >= nmax) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Index %D's value %D is larger than maximum given %D",i,indices[i],nmax);
  }
#endif
  /* Count number of unique entries */
  unique = (n>0);
  for (i=0; i<n-1; i++) {
    if (indices[i+1] != indices[i]) unique++;
  }
  ierr = PetscMalloc1(nmax-nmin-unique,&nindices);CHKERRQ(ierr);
  cnt  = 0;
  for (i=nmin,j=0; i<nmax; i++) {
    if (j<n && i==indices[j]) do { j++; } while (j<n && i==indices[j]);
    else nindices[cnt++] = i;
  }
  if (cnt != nmax-nmin-unique) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Number of entries found in complement %D does not match expected %D",cnt,nmax-nmin-unique);
  ierr = ISCreateGeneral(PetscObjectComm((PetscObject)is),cnt,nindices,PETSC_OWN_POINTER,isout);CHKERRQ(ierr);
  ierr = ISRestoreIndices(is,&indices);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

/* Compose an IS with an ISLocalToGlobalMapping to map from IS source indices to global indices */
static PetscErrorCode ISL2GCompose(IS is,ISLocalToGlobalMapping ltog,ISLocalToGlobalMapping *cltog)
{
  PetscErrorCode ierr;
  const PetscInt *idx;
  PetscInt       m,*idxm;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(is,IS_CLASSID,1);
  PetscValidHeaderSpecific(ltog,IS_LTOGM_CLASSID,2);
  PetscValidPointer(cltog,3);
  ierr = ISGetLocalSize(is,&m);CHKERRQ(ierr);
  ierr = ISGetIndices(is,&idx);CHKERRQ(ierr);
  ierr = PetscMalloc1(m,&idxm);CHKERRQ(ierr);
  if (ltog) {
    ierr = ISLocalToGlobalMappingApply(ltog,m,idx,idxm);CHKERRQ(ierr);
  } else {
    ierr = PetscMemcpy(idxm,idx,m*sizeof(PetscInt));CHKERRQ(ierr);
  }
  ierr = ISLocalToGlobalMappingCreate(PetscObjectComm((PetscObject)is),m,idxm,PETSC_OWN_POINTER,cltog);CHKERRQ(ierr);
  ierr = ISRestoreIndices(is,&idx);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}

static PetscErrorCode ISToGeneral_Block(IS inis)
{
  IS_Block       *sub   = (IS_Block*)inis->data;
  PetscInt       bs,n;
  const PetscInt *idx;
  PetscErrorCode ierr;

  PetscFunctionBegin;
  ierr = ISGetBlockSize(inis,&bs);CHKERRQ(ierr);
  ierr = ISGetLocalSize(inis,&n);CHKERRQ(ierr);
  ierr = ISGetIndices(inis,&idx);CHKERRQ(ierr);
  if (bs == 1) {
    PetscCopyMode mode = sub->allocated ? PETSC_OWN_POINTER : PETSC_USE_POINTER;
    sub->allocated = PETSC_FALSE; /* prevent deallocation when changing the subtype*/
    ierr = ISSetType(inis,ISGENERAL);CHKERRQ(ierr);
    ierr = ISGeneralSetIndices(inis,n,idx,mode);CHKERRQ(ierr);
  } else {
    ierr = ISSetType(inis,ISGENERAL);CHKERRQ(ierr);
    ierr = ISGeneralSetIndices(inis,n,idx,PETSC_OWN_POINTER);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

PetscErrorCode DMLabelPermute(DMLabel label, IS permutation, DMLabel *labelNew)
{
  const PetscInt *perm;
  PetscInt        numValues, numPoints, v, q;
  PetscErrorCode  ierr;

  PetscFunctionBegin;
  ierr = DMLabelMakeAllValid_Private(label);CHKERRQ(ierr);
  ierr = DMLabelDuplicate(label, labelNew);CHKERRQ(ierr);
  ierr = DMLabelGetNumValues(*labelNew, &numValues);CHKERRQ(ierr);
  ierr = ISGetLocalSize(permutation, &numPoints);CHKERRQ(ierr);
  ierr = ISGetIndices(permutation, &perm);CHKERRQ(ierr);
  for (v = 0; v < numValues; ++v) {
    const PetscInt size   = (*labelNew)->stratumSizes[v];
    const PetscInt *points;
    PetscInt *pointsNew;

    ierr = ISGetIndices((*labelNew)->points[v],&points);CHKERRQ(ierr);
    ierr = PetscMalloc1(size,&pointsNew);CHKERRQ(ierr);
    for (q = 0; q < size; ++q) {
      const PetscInt point = points[q];

      if ((point < 0) || (point >= numPoints)) SETERRQ2(PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Label point %D is not in [0, %D) for the remapping", point, numPoints);
      pointsNew[q] = perm[point];
    }
    ierr = ISRestoreIndices((*labelNew)->points[v],&points);CHKERRQ(ierr);
    ierr = PetscSortInt(size, pointsNew);CHKERRQ(ierr);
    ierr = ISDestroy(&((*labelNew)->points[v]));CHKERRQ(ierr);
    ierr = ISCreateGeneral(PETSC_COMM_SELF,size,pointsNew,PETSC_OWN_POINTER,&((*labelNew)->points[v]));CHKERRQ(ierr);
    ierr = PetscObjectSetName((PetscObject) ((*labelNew)->points[v]), "indices");CHKERRQ(ierr);
  }
  ierr = ISRestoreIndices(permutation, &perm);CHKERRQ(ierr);
  if (label->bt) {
    ierr = PetscBTDestroy(&label->bt);CHKERRQ(ierr);
    ierr = DMLabelCreateIndex(label, label->pStart, label->pEnd);CHKERRQ(ierr);
  }
  PetscFunctionReturn(0);
}

/*@
   ISGetNonlocalIS - Gather all nonlocal indices for this IS and present
                     them as another sequential index set.


   Collective on IS

   Input Parameter:
.  is - the index set

   Output Parameter:
.  complement - sequential IS with indices identical to the result of
                ISGetNonlocalIndices()

   Level: intermediate

   Notes: complement represents the result of ISGetNonlocalIndices as an IS.
          Therefore scalability issues similar to ISGetNonlocalIndices apply.
          The resulting IS must be restored using ISRestoreNonlocalIS().

   Concepts: index sets^getting nonlocal indices
.seealso: ISGetNonlocalIndices(), ISRestoreNonlocalIndices(),  ISAllGather(), ISGetSize()
@*/
PetscErrorCode  ISGetNonlocalIS(IS is, IS *complement)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(is,IS_CLASSID,1);
  PetscValidPointer(complement,2);
  /* Check if the complement exists already. */
  if (is->complement) {
    *complement = is->complement;
    ierr = PetscObjectReference((PetscObject)(is->complement));CHKERRQ(ierr);
  } else {
    PetscInt       N, n;
    const PetscInt *idx;
    ierr = ISGetSize(is, &N);CHKERRQ(ierr);
    ierr = ISGetLocalSize(is,&n);CHKERRQ(ierr);
    ierr = ISGetNonlocalIndices(is, &idx);CHKERRQ(ierr);
    ierr = ISCreateGeneral(PETSC_COMM_SELF, N-n,idx, PETSC_USE_POINTER, &(is->complement));CHKERRQ(ierr);
    ierr = PetscObjectReference((PetscObject)is->complement);CHKERRQ(ierr);
    *complement = is->complement;
  }
  PetscFunctionReturn(0);
}