17.2.50. MPI_Comm_create_from_group

MPI_Comm_create_from_group - Creates a new communicator from a group and stringtag

17.2.50.1. Syntax

17.2.50.1.1. C Syntax

#include <mpi.h>

int MPI_Comm_create_from_group(MPI_Group group, const char *stringtag, MPI_Info info, MPI_Errhandler errhandler, MPI_Comm *newcomm)

17.2.50.1.2. Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_COMM_CREATE_FROM_GROUP(GROUP, STRINGTAG, INFO, ERRHANDLER, NEWCOMM, IERROR)
    INTEGER GROUP, INFO, ERRHANDLER, NEWCOMM, IERROR
    CHARACTER*(*) STRINGTAG

17.2.50.1.3. Fortran 2008 Syntax

USE mpi_f08

MPI_Comm_create_from_group(group, stringtag, info, errhandler, newcomm, ierror)
    TYPE(MPI_Group), INTENT(IN) :: group
    CHARACTER(LEN=*), INTENT(IN) :: stringtag
    TYPE(MPI_Info), INTENT(IN) :: info
    TYPE(MPI_Errhandler), INTENT(IN) :: errhandler
    TYPE(MPI_Comm), INTENT(OUT) :: newcomm
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

17.2.50.2. Input Parameters

  • group : Group (handler)

  • stringtag : Unique identifier for this operation (string)

  • info : info object (handler)

  • errhandler : error handler to be attached to the new intra-communicator (handle)

17.2.50.3. Output Parameters

  • newcomm : New communicator (handle).

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

17.2.50.4. Description

MPI_Comm_create_from_group is similar to MPI_Comm_create_group, except that the set of MPI processes involved in the creation of the new intra-communicator is specified by a group argument, rather than the group associated with a pre-existing communicator. If a non-empty group is specified, then all MPI processes in that group must call the function and each of these MPI processes must provide the same arguments, including a group that contains the same members with the same ordering, and identical stringtag value. In the event that MPI_GROUP_EMPTY is supplied as the group argument, then the call is a local operation and MPI_COMM_NULL is returned as newcomm. The stringtag argument is analogous to the tag used for MPI_Comm_create_group. If multiple threads at a given MPI process perform concurrent MPI_Comm_create_from_group operations, the user must distinguish these operations by providing different stringtag arguments. The stringtag shall not exceed MPI_MAX_STRINGTAG_LEN characters in length. For C, this includes space for a null terminating character.

17.2.50.5. Notes

The errhandler argument specifies an error handler to be attached to the new intracommunicator. The info argument provides hints and assertions, possibly MPI implementation dependent, which indicate desired characteristics and guide communicator creation. MPI_MAX_STRINGTAG_LEN shall have a value of at least 63.

17.2.50.6. 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.