MPI_Intercomm_create(3) MPI MPI_Intercomm_create(3) NAME MPI_Intercomm_create - Creates an intercommuncator from two intracommuni- cators SYNOPSIS int MPI_Intercomm_create(MPI_Comm local_comm, int local_leader, MPI_Comm peer_comm, int remote_leader, int tag, MPI_Comm *newintercomm) INPUT PARAMETERS local_comm - local intra-communicator (handle) local_leader - rank of local group leader in local_comm (integer) peer_comm - `peer communicator; significant only at the local_leader (handle) remote_leader - rank of remote group leader in peer_comm; significant only at the local_leader (integer) tag - tag (integer) OUTPUT PARAMETERS newintercomm - new inter-communicator (handle) NOTES peer_comm is significant only for the process designated the local_leader in the local_comm . The MPI 1.1 Standard contains two mutually exclusive comments on the input intercommunicators. One says that their respective groups must be dis- joint; the other that the leaders can be the same process. After some dis- cussion by the MPI Forum, it has been decided that the groups must be dis- joint. Note that the reason given for this in the standard is not the rea- son for this choice; rather, the other operations on intercommunicators (like MPI_Intercomm_merge ) do not make sense if the groups are not dis- joint. THREAD AND INTERRUPT SAFETY This routine is thread-safe. This means that this routine may be safely used by multiple threads without the need for any user-provided thread locks. However, the routine is not interrupt safe. Typically, this is due to the use of memory allocation routines such as malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. 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 inte- ger 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 state- ment. All MPI objects (e.g., MPI_Datatype , MPI_Comm ) are of type INTEGER in Fortran. ERRORS 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 ar- gument. Before the value is returned, the current MPI error handler is called. By default, this error handler aborts the MPI job. The error han- dler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated. 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; however, MPI implementations will attempt to continue whenever possible. MPI_SUCCESS - No error; MPI routine completed successfully. MPI_ERR_ARG - Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK ). MPI_ERR_COMM - Invalid communicator. A common error is to use a null communica- tor in a call (not even allowed in MPI_Comm_rank ). MPI_ERR_TAG - Invalid tag argument. Tags must be non-negative; tags in a re- ceive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also be MPI_ANY_TAG . The largest tag value is available through the the attribute MPI_TAG_UB . MPI_ERR_OTHER - Other error; use MPI_Error_string to get more information about this error code. SEE ALSO MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group, MPI_Comm_re- mote_size 4/10/2026 MPI_Intercomm_create(3)
NAME | SYNOPSIS | INPUT PARAMETERS | OUTPUT PARAMETERS | NOTES | THREAD AND INTERRUPT SAFETY | NOTES FOR FORTRAN | ERRORS | SEE ALSO
Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=MPI_Intercomm_create&sektion=3&manpath=FreeBSD+Ports+15.1.quarterly>