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MPI_Cart_sub(3)                       MPI                      MPI_Cart_sub(3)


NAME

       MPI_Cart_sub -  Partitions a communicator into subgroups which  form
       lower-dimensional cartesian subgrids


SYNOPSIS

       int MPI_Cart_sub(MPI_Comm comm, MPICH2_CONST int *remain_dims, MPI_Comm *comm_new)


INPUT PARAMETERS

       comm   - communicator with cartesian structure (handle)
       remain_dims
              - the i th entry of remain_dims specifies whether the i th
              dimension is kept in the subgrid (true) or is dropped (false)
              (logical vector)


OUTPUT PARAMETER

       newcomm
              - communicator containing the subgrid that includes the calling
              process (handle)


THREAD AND INTERRUPT SAFETY

       This routine is thread-safe.  This means that this routine may be
       safely used by multiple threads without the need for any user-provided
       thread locks.  However, the routine is not interrupt safe.  Typically,
       this is due to the use of memory allocation routines such as malloc or
       other non-MPICH runtime routines that are themselves not interrupt-
       safe.


NOTES FOR FORTRAN

       All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK ) have
       an additional argument ierr at the end of the argument list.  ierr is
       an integer and has the same meaning as the return value of the routine
       in C.  In Fortran, MPI routines are subroutines, and are invoked with
       the call statement.

       All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in
       Fortran.


ERRORS

       All MPI routines (except MPI_Wtime and MPI_Wtick ) return an error
       value; C routines as the value of the function and Fortran routines in
       the last argument.  Before the value is returned, the current MPI error
       handler is called.  By default, this error handler aborts the MPI job.
       The error handler may be changed with MPI_Comm_set_errhandler (for
       communicators), MPI_File_set_errhandler (for files), and
       MPI_Win_set_errhandler (for RMA windows).  The MPI-1 routine
       MPI_Errhandler_set may be used but its use is deprecated.  The
       predefined error handler MPI_ERRORS_RETURN may be used to cause error
       values to be returned.  Note that MPI does not guarentee that an MPI
       program can continue past an error; however, MPI implementations will
       attempt to continue whenever possible.

       MPI_SUCCESS
              - No error; MPI routine completed successfully.
       MPI_ERR_TOPOLOGY
              - Invalid topology.  Either there is no topology associated with
              this communicator, or it is not the correct type (e.g., MPI_CART
              when expecting MPI_GRAPH ).
       MPI_ERR_COMM
              - Invalid communicator.  A common error is to use a null
              communicator in a call (not even allowed in MPI_Comm_rank ).
       MPI_ERR_ARG
              - Invalid argument.  Some argument is invalid and is not
              identified by a specific error class (e.g., MPI_ERR_RANK ).


LOCATION

       src/mpi/topo/cart_sub.c

                                   9/20/2012                   MPI_Cart_sub(3)

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