Ubuntu Manpage: MPI_Comm_split_type - Creates new communicators based on colors and keys.

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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.