Creates an intracommuncator from an intercommunicator


#include "mpi.h"
int MPI_Intercomm_merge ( comm, high, comm_out )
MPI_Comm  comm;
int       high;
MPI_Comm *comm_out;

Input Parameters

comm Intercommunicator
high Used to order the groups of the two intracommunicators within comm when creating the new communicator.

Output Parameter

Created intracommunicator

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.


 1) Allocate two contexts 
 2) Local and remote group leaders swap high values
 3) Determine the high value.
 4) Merge the two groups and make the intra-communicator


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_Errhandler_set; 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.

No error; MPI routine completed successfully.
Invalid communicator. A common error is to use a null communicator in a call (not even allowed in MPI_Comm_rank).
This error is returned when some part of the MPICH implementation is unable to acquire memory.

See Also

MPI_Intercomm_create, MPI_Comm_free