NAME

MPI_Comm_splits - Splits a communicator

SYNOPSIS

#include <mpi.h> 
int MPI_Comm_split(MPI_Comm comm , int split_key , int key , MPI_Comm *out ); 
#include <pmpi.h> 
int PMPI_Comm_split(MPI_Comm comm , int split_key , int key , MPI_Comm *out ); 

INPUT PARAMETERS

comm - communicator (handle)

split_key - key to split communicator by (integer)

key - key to order processes in new communicators (integer)

OUTPUT PARAMETER

out - the new communicator that this process belongs to (handle).

DESCRIPTION

The MPI_Comm_split() function is used to split a communicator comm into smaller sub-communicators. This is done by using split_key . Processes that pass the same split_key will become members of the same output communicator. However, if a process passes a split_key with the value MPI_UNDEFINED then MPI_COMM_NULL will be returned. Once the size and membership of the communicators are determined, then key is used to order the processes within them. The new communicator that the current process belongs to is returned in result .

Note that the communicator must be valid (not MPI_COMM_NULL). PMPI_Comm_split() is the profiling version of this function.

ERRORS

All MPI routines except for MPI_Wtime and MPI_Wtick return an error value. The the current MPI error handler is invoked if this return value is not MPI_SUCCESS. The default error handler aborts, but this may be changed with by using the MPI_Errhandler_set() function. The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. Note that MPI does not guarentee that an MPI program can continue past an error. In this implementation, all errors except MPI_ERR_INTERN or MPI_ERR_OTHER should always be recoverable.

MPI_SUCCESS - No error;

MPI_ERR_COMM - Invalid communicator;

MPI_ERR_ARG - Invalid output pointer;

MPI_ERR_INTERN - Out of Memory. This may be fatal.

SEE ALSO

MPI_Comm_dup (3) MPI_Comm_create (3) MPI_Comm_free (3) MPI_Intercomm_create (3)

• Lockless
• MPI Documentation
• MPI_Comm_split