MPI_Intercomm_create(3) LAM/MPI MPI_Intercomm_create(3)
MPI_Intercomm_create - Creates an intercommuncator from two intracommunicators
int MPI_Intercomm_create(MPI_Comm lcomm, int lleader,
MPI_Comm pcomm, int pleader, int tag,
lcomm - Local (intra)communicator
- Rank in local_comm of leader (often 0)
pcomm - Remote communicator
- Rank in peer_comm of remote leader (often 0)
tag - Message tag to use in constructing intercommunicator; if multiple MPI_Intercomm_creates are being made, they should use different
tags (more precisely, ensure that the local and remote leaders are using different tags for each MPI_intercomm_create ).
- Created intercommunicator
The MPI 1.1 Standard contains two mutually exclusive comments on the input intracommunicators. One says that their repective groups must
be disjoint; the other that the leaders can be the same process. After some discussion by the MPI Forum, it has been decided that the
groups must be disjoint. Note that the reason given for this in the standard is not the reason for this choice; rather, the other opera-
tions on intercommunicators (like MPI_Intercomm_merge ) do not make sense if the groups are not disjoint.
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.
If an error occurs in an MPI function, the current MPI error handler is called to handle it. 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 (in C and Fortran; this error handler is less useful in with the C++ MPI bindings. The predefined error handler
MPI::ERRORS_THROW_EXCEPTIONS should be used in C++ if the error value needs to be recovered). Note that MPI does not guarantee that an MPI
program can continue past an error.
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. The C++ bindings for MPI do not return error values; instead, error values are communicated by throwing exceptions of
type MPI::Exception (but not by default). Exceptions are only thrown if the error value is not MPI::SUCCESS
Note that if the MPI::ERRORS_RETURN handler is set in C++, while MPI functions will return upon an error, there will be no way to recover
what the actual error value was.
- 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 ).
- Invalid tag argument. Tags must be non-negative; tags in a receive ( MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also be
. The largest tag value is available through the the attribute MPI_TAG_UB
- Invalid argument. Some argument is invalid and is not identified by a specific error class. This is typically a NULL pointer or
other such error.
- This error is returned when some part of the LAM/MPI implementation is unable to acquire memory.
- Invalid source or destination rank. Ranks must be between zero and the size of the communicator minus one; ranks in a receive (
MPI_Recv , MPI_Irecv , MPI_Sendrecv , etc.) may also be MPI_ANY_SOURCE
MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group,
For more information, please see the official MPI Forum web site, which contains the text of both the MPI-1 and MPI-2 standards. These
documents contain detailed information about each MPI function (most of which is not duplicated in these man pages).
The LAM Team would like the thank the MPICH Team for the handy program to generate man pages ("doctext" from ftp://ftp.mcs.anl.gov/pub/sow-
ing/sowing.tar.gz ), the initial formatting, and some initial text for most of the MPI-1 man pages.
LAM/MPI 6.5.8 11/10/2002 MPI_Intercomm_create(3)