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mpi_cart_sub(3openmpi) [osx man page]

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)

Check Out this Related Man Page

MPI_Cart_get(3OpenMPI)													    MPI_Cart_get(3OpenMPI)

NAME

       MPI_Cart_get -  Retrieves Cartesian topology information associated with a communicator.

SYNTAX

C Syntax
       #include <mpi.h>
       int MPI_Cart_get(MPI_Comm comm, int maxdims, int *dims, int *periods,
	    int *coords)

Fortran Syntax
       INCLUDE 'mpif.h'
       MPI_CART_GET(COMM, MAXDIMS, DIMS, PERIODS, COORDS, IERROR)
	    INTEGER   COMM, MAXDIMS, DIMS(*), COORDS(*), IERROR
	    LOGICAL   PERIODS(*)

C++ Syntax
       #include <mpi.h>
       void Cartcomm::Get_topo(int maxdims, int dims[],
	    bool periods[], int coords[]) const

INPUT PARAMETERS

       comm	 Communicator with Cartesian structure (handle).

       maxdims	 Length of vectors dims, periods, and coords in the calling program (integer).

OUTPUT PARAMETERS

       dims	 Number of processes for each Cartesian dimension (array of integers).

       periods	 Periodicity (true/false) for each Cartesian dimension (array of logicals).

       coords	 Coordinates of calling process in Cartesian structure (array of integers).

       IERROR	 Fortran only: Error status (integer).

DESCRIPTION

       The  functions  MPI_Cartdim_get	and  MPI_Cart_get  return  the	Cartesian  topology information that was associated with a communicator by
       MPI_Cart_create.

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_Cartdim_get
       MPI_Cart_create

Open MPI 1.2							  September 2006					    MPI_Cart_get(3OpenMPI)
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