petsc-3.10.5 2019-03-28
Report Typos and Errors

# PetscSubcomm

A decomposition of an MPI communicator into subcommunicators

### Synopsis

    typedef struct _n_PetscSubcomm* PetscSubcomm;

### Notes

After a call to PetscSubcommSetType(), PetscSubcommSetTypeGeneral(), or PetscSubcommSetFromOptions() one may call

        PetscSubcommChild() returns the associated subcommunicator on this process

        PetscSubcommContiguousParent() returns a parent communitor but with all child of the same subcommunicator having contiguous rank

### Sample Usage

PetscSubcommCreate() PetscSubcommSetNumber() PetscSubcommSetType(PETSC_SUBCOMM_INTERLACED); ccomm = PetscSubcommChild() PetscSubcommDestroy()

### Notes

      PETSC_SUBCOMM_GENERAL - similar to MPI_Comm_split() each process sets the new communicator (color) they will belong to and the order within that communicator

      PETSC_SUBCOMM_CONTIGUOUS - each new communicator contains a set of process with contiguous ranks in the original MPI communicator

      PETSC_SUBCOMM_INTERLACED - each new communictor contains a set of processes equally far apart in rank from the others in that new communicator

Example: Consider a communicator with six processes split into 3 subcommunicators.

        PETSC_SUBCOMM_CONTIGUOUS - the first communicator contains rank 0,1  the second rank 2,3 and the third rank 4,5 in the original ordering of the original communicator

        PETSC_SUBCOMM_INTERLACED - the first communicator contains rank 0,3, the second 1,4 and the third 2,5

### Developer Notes

This is used in objects such as PCREDUNDANT to manage the subcommunicators on which the redundant computations are performed.

### See Also

PetscSubcommCreate(), PetscSubcommSetNumber(), PetscSubcommSetType(), PetscSubcommView(), PetscSubcommSetFromOptions()

### Level

advanced

### Location

include/petscsys.h
Index of all Sys routines
Table of Contents for all manual pages
Index of all manual pages