osx man page for mpi_cart_sub

MPI_Cart_sub(3OpenMPI)													    MPI_Cart_sub(3OpenMPI)

NAME
       MPI_Cart_sub  - Partitions a communicator into subgroups, which form lower-dimensional Cartesian subgrids.

SYNTAX
C Syntax
       #include <mpi.h>
       int MPI_Cart_sub(MPI_Comm comm, int *remain_dims, MPI_Comm *comm_new)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_CART_SUB(COMM, REMAIN_DIMS, COMM_NEW, IERROR)
	    INTEGER   COMM, COMM_NEW, IERROR
	    LOGICAL   REMAIN_DIMS(*)

C++ Syntax
       #include <mpi.h>
       Cartcomm Cartcomm::Sub(const bool remain_dims[]) const

INPUT PARAMETERS
       comm	 Communicator with Cartesian structure (handle).

       remain_dims
		 The  ith  entry  of  remain_dims specifies whether the ith dimension is kept in the subgrid (true) or is dropped (false) (logical
		 vector).

OUTPUT PARAMETERS
       comm_new  Communicator containing the subgrid that includes the calling process (handle).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION
       If a Cartesian topology has been created with MPI_Cart_create, the function  MPI_Cart_sub can be used to partition the  communicator  group
       into  subgroups	that  form lower-dimensional Cartesian subgrids, and to build for each subgroup a communicator with the associated subgrid
       Cartesian topology. (This function is closely related to MPI_Comm_split.)

       Example: Assume that  MPI_Cart_create( ..., comm) has defined a (2 x 3 x 4)   grid. Let	remain_dims = (true, false, true). Then a call to

	   MPI_Cart_sub(comm, remain_dims, comm_new)

       will create three communicators, each with eight processes in a 2 x 4 Cartesian topology. If remain_dims = (false, false,  true)  then  the
       call  to  MPI_Cart_sub(comm, remain_dims, comm_new) will create six nonoverlapping communicators, each with four processes, in a one-dimen-
       sional Cartesian topology.

ERRORS
       Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument. C++ func-
       tions  do not return errors. If the default error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then on error the C++ exception mechanism
       will be used to throw an MPI:Exception object.

       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.

SEE ALSO
       MPI_Cart_create
       MPI_Comm_split

Open MPI 1.2							  September 2006					    MPI_Cart_sub(3OpenMPI)