NAME

       MPI_Comm_create - Creates a new communicator.

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Comm_create(MPI_Comm comm, MPI_Group group, MPI_Comm *newcomm)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_COMM_CREATE(COMM, GROUP, NEWCOMM, IERROR)
            INTEGER   COMM, GROUP, NEWCOMM, IERROR

C++ Syntax

       #include <mpi.h>
       MPI::Intercomm MPI::Intercomm::Create(const Group& group) const

       MPI::Intracomm MPI::Intracomm::Create(const Group& group) const

INPUT PARAMETER

       comm      Communicator (handle).

       group     Group, which is a subset of the group of comm (handle).

OUTPUT PARAMETERS

       newcomm   New communicator (handle).

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       This function creates a new communicator newcomm with communication group defined by group
       and a new context. The function sets newcomm to a new  communicator  that  spans  all  the
       processes  that are in the group.  It sets newcomm to MPI_COMM_NULL for processes that are
       not in the group.

       Each process must call with a group argument that is a subgroup of  the  group  associated
       with  comm;  this could be MPI_GROUP_EMPTY. The processes may specify different values for
       the group argument. If a process calls with a non-empty group, then all processes in  that
       group  must call the function with the same group as argument, that is: the same processes
       in the same order. Otherwise the call is erroneous.

NOTES

       MPI_Comm_create provides a means of making a  subset  of  processes  for  the  purpose  of
       separate MIMD computation, with separate communication space. newcomm, which is created by
       MPI_Comm_create, can be used in subsequent calls to MPI_Comm_create (or other communicator
       constructors)  to  further  subdivide a computation into parallel sub-computations. A more
       general service is provided by MPI_Comm_split.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and
       Fortran  routines in the last argument. C++ functions do not return errors. If the default
       error handler is set to MPI::ERRORS_THROW_EXCEPTIONS, then  on  error  the  C++  exception
       mechanism will be used to throw an MPI::Exception object.

       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.

SEE ALSO

       MPI_Comm_split

       MPI_Intercomm_create MPI_Comm_create_group