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MPI_Cart_sub(3) man page (version 1.2.9)

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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 dimen-
                 sion  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 nonover-
       lapping communicators, each with four processes, in  a  one-dimensional
       Cartesian topology.

       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)

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