ISLocalToGlobalMappingCreate#

Creates a mapping between a local (0 to n) ordering and a global parallel ordering.

Synopsis#

#include "petscis.h"  
PetscErrorCode ISLocalToGlobalMappingCreate(MPI_Comm comm, PetscInt bs, PetscInt n, const PetscInt indices[], PetscCopyMode mode, ISLocalToGlobalMapping *mapping)

Not Collective, but communicator may have more than one process

Input Parameters#

comm - MPI communicator
bs - the block size
n - the number of local elements divided by the block size, or equivalently the number of block indices
indices - the global index for each local element, these do not need to be in increasing order (sorted), these values should not be scaled (i.e. multiplied) by the blocksize bs
mode - see PetscCopyMode

Output Parameter#

mapping - new mapping data structure

Notes#

There is one integer value in indices per block and it represents the actual indices bs*idx + j, where j=0,..,bs-1

For “small” problems when using ISGlobalToLocalMappingApply() and ISGlobalToLocalMappingApplyBlock(), the ISLocalToGlobalMappingType of ISLOCALTOGLOBALMAPPINGBASIC will be used; this uses more memory but is faster; this approach is not scalable for extremely large mappings.

For large problems ISLOCALTOGLOBALMAPPINGHASH is used, this is scalable. Use ISLocalToGlobalMappingSetType() or call ISLocalToGlobalMappingSetFromOptions() with the option -islocaltoglobalmapping_type <basic,hash> to control which is used.