NAME

MPI_Comm_split_type - Creates new communicators based on colors and keys.

SYNTAX

C Syntax

#include <mpi.h>
int MPI_Comm_split_type(MPI_Comm comm, int split_type, int key,
	MPI_Info info, MPI_Comm *newcomm)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_SPLIT_TYPE(COMM, SPLIT_TYPE, KEY, INFO, NEWCOMM, IERROR)
	INTEGER	COMM, SPLIT_TYPE, KEY, INFO, NEWCOMM, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Comm_split_type(comm, split_type, key, info, newcomm, ierror)
	TYPE(MPI_Comm), INTENT(IN) :: comm
	INTEGER, INTENT(IN) :: split_type, key
	TYPE(MPI_Info), INTENT(IN) :: info
	TYPE(MPI_Comm), INTENT(OUT) :: newcomm
	INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

comm: Communicator (handle).
split_type: Type of processes to be grouped together (integer).
key: Control of rank assignment (integer).
info: Info argument (handle).

OUTPUT PARAMETERS

newcomm: New communicator (handle).
IERROR: Fortran only: Error status (integer).

DESCRIPTION

This function partitions the group associated with comm into disjoint subgroups, based on the type specied by split_type. Each subgroup contains all processes of the same type. Within each subgroup, the processes are ranked in the order defined by the value of the argument key, with ties broken according to their rank in the old group. A new communicator is created for each subgroup and returned in newcomm. This is a collective call; all processes must provide the same split_type, but each process is permitted to provide different values for key. An exception to this rule is that a process may supply the type value MPI_UNDEFINED, in which case newcomm returns MPI_COMM_NULL.

SPLIT TYPES

MPI_COMM_TYPE_SHARED: This type splits the communicator into subcommunicators, each of which can create a shared memory region.
OMPI_COMM_TYPE_NODE: Synonym for MPI_COMM_TYPE_SHARED.
OMPI_COMM_TYPE_HWTHREAD: This type splits the communicator into subcommunicators, each of which belongs to the same hardware thread.
OMPI_COMM_TYPE_CORE: This type splits the communicator into subcommunicators, each of which belongs to the same core/processing unit.
OMPI_COMM_TYPE_L1CACHE: This type splits the communicator into subcommunicators, each of which belongs to the same L1 cache.
OMPI_COMM_TYPE_L2CACHE: This type splits the communicator into subcommunicators, each of which belongs to the same L2 cache.
OMPI_COMM_TYPE_L3CACHE: This type splits the communicator into subcommunicators, each of which belongs to the same L3 cache.
OMPI_COMM_TYPE_SOCKET: This type splits the communicator into subcommunicators, each of which belongs to the same socket.
OMPI_COMM_TYPE_NUMA: This type splits the communicator into subcommunicators, each of which belongs to the same NUMA-node.
OMPI_COMM_TYPE_BOARD: This type splits the communicator into subcommunicators, each of which belongs to the same board.
OMPI_COMM_TYPE_HOST: This type splits the communicator into subcommunicators, each of which belongs to the same host.
OMPI_COMM_TYPE_CU: This type splits the communicator into subcommunicators, each of which belongs to the same computational unit.
OMPI_COMM_TYPE_CLUSTER: This type splits the communicator into subcommunicators, each of which belongs to the same cluster.

NOTES

The communicator keys denoted with an OMPI_ prefix instead of an MPI_ prefix are specific to Open MPI, and are not part of the MPI standard. Their use should be protected by the OPEN_MPI C preprocessor macro.

ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

Before the error value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job, except for I/O function errors. The error handler may be changed with MPI_Comm_set_errhandler; the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error.