17.2.234. MPI_Intercomm_merge

MPI_Intercomm_merge - Creates an intracommunicator from an intercommunicator.

17.2.234.1. SYNTAX

17.2.234.1.1. C Syntax

#include <mpi.h>

int MPI_Intercomm_merge(MPI_Comm intercomm, int high,
     MPI_Comm *newintracomm)

17.2.234.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_INTERCOMM_MERGE(INTERCOMM, HIGH, NEWINTRACOMM, IERROR)
     INTEGER INTERCOMM, NEWINTRACOMM, IERROR
     LOGICAL HIGH

17.2.234.1.3. Fortran 2008 Syntax

USE mpi_f08
MPI_Intercomm_merge(intercomm, high, newintracomm, ierror)
     TYPE(MPI_Comm), INTENT(IN) :: intercomm
     LOGICAL, INTENT(IN) :: high
     TYPE(MPI_Comm), INTENT(OUT) :: newintracomm
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.234.2. INPUT PARAMETERS

  • intercomm: Intercommunicator (type indicator).

  • high: Used to order the groups of the two intracommunicators within comm when creating the new communicator (type indicator).

17.2.234.3. OUTPUT PARAMETERS

  • newintracomm: Created intracommunicator (type indicator).

  • IERROR: Fortran only: Error status (integer).

17.2.234.4. DESCRIPTION

This function creates an intracommunicator from the union of the two groups that are associated with intercomm. All processes should provide the same high value within each of the two groups. If processes in one group provide the value high = false and processes in the other group provide the value high = true, then the union orders the “low” group before the “high” group. If all processes provide the same high argument, then the order of the union is arbitrary. This call is blocking and collective within the union of the two groups.

17.2.234.5. ERRORS

Almost all MPI routines return an error value; C routines as the value of the function and Fortran routines in the last argument.

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.