NAME

MPI_Intercomm_merge - Creates an intracommunicator by merging an intercommunicator

SYNOPSIS

#include <mpi.h> 
int MPI_Intercomm_merge(MPI_Comm comm , int high , comm *out ); 
#include <pmpi.h> 
int PMPI_Intercomm_merge(MPI_Comm comm , int high , comm *out ); 

INPUT PARAMETERS

comm - intercommunicator (handle)

high - order parameter (boolean)

OUTPUT PARAMETER

out - the resulting intracommunicator (handle).

DESCRIPTION

The MPI_Intercomm_merge() function is used to merge the local and remote groups within an intercommunicator comm into a single group. That new group is used to create an intracommunicator out . The value of high is used to order the ranks in the new intracommunicator. All processes in the same group should provide the same value of this parameter. If all processes in one group provide a value of high = false and all processes in the other group provide high = true then the union orders all process in the "low" group before the "high" group.

Note that the communicator must be a valid one (not MPI_COMM_NULL). PMPI_Intercomm_merge() 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, high parameter not 0 or 1, or high varies in a group;

MPI_ERR_INTERN - Out of memory. This may be fatal;

SEE ALSO

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

• Lockless
• MPI Documentation
• MPI_Intercomm_merge