NAME
MPI_Intercomm_create - Creates an intercommuncator from two
intracommunicators
SYNOPSIS
#include <mpi.h>
int MPI_Intercomm_create(MPI_Comm lcomm, int lleader,
MPI_Comm pcomm, int pleader, int tag,
MPI_Comm *newcomm)
INPUT PARAMTERS
lcomm - Local (intra)communicator
lleader
- Rank in local_comm of leader (often 0)
pcomm - Remote communicator
pleader
- 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
).
OUTPUT PARAMETER
newcomm
- Created intercommunicator
NOTES
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 operations 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.
ERRORS
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.
MPI_SUCCESS
- No error; MPI routine completed successfully.
MPI_ERR_COMM
- Invalid communicator. A common error is to use a null
communicator in a call (not even allowed in MPI_Comm_rank ).
MPI_ERR_TAG
- Invalid tag argument. Tags must be non-negative; tags in a
receive ( 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_ARG
- 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.
MPI_ERR_OTHER
- This error is returned when some part of the LAM/MPI
implementation is unable to acquire memory.
MPI_ERR_RANK
- 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 .
SEE ALSO
MPI_Intercomm_merge, MPI_Comm_free, MPI_Comm_remote_group,
MPI_Comm_remote_size
MORE INFORMATION
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).
http://www.mpi-forum.org/
ACKNOWLEDGEMENTS
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/sowing/sowing.tar.gz ), the initial
formatting, and some initial text for most of the MPI-1 man pages.
LOCATION
iccreate.c