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.TH "MPI_COMM_SET_NAME" "3" "May 30, 2025" "" "Open MPI"
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.sp
\fI\%MPI_Comm_set_name\fP — Associates a name with a communicator.
.SH SYNTAX
.SS C Syntax
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.INDENT 3.5
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.nf
.ft C
#include <mpi.h>

int MPI_Comm_set_name(MPI_Comm comm, const char *comm_name)
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.SS Fortran Syntax
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.nf
.ft C
USE MPI
! or the older form: INCLUDE \(aqmpif.h\(aq
MPI_COMM_SET_NAME(COMM, COMM_NAME, IERROR)
     INTEGER COMM, IERROR
     CHARACTER*(*) COMM_NAME
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.fi
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.SS Fortran 2008 Syntax
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.ft C
USE mpi_f08
MPI_Comm_set_name(comm, comm_name, ierror)
     TYPE(MPI_Comm), INTENT(IN) :: comm
     CHARACTER(LEN=*), INTENT(IN) :: comm_name
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror
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.fi
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.SH INPUT/OUTPUT PARAMETER
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.IP \(bu 2
\fBcomm\fP: Communicator whose identifier is to be set (handle).
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.SH INPUT PARAMETER
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.IP \(bu 2
\fBcomm_name\fP: Character string to be used as the identifier for the communicator (string).
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.SH OUTPUT PARAMETER
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.IP \(bu 2
\fBierror\fP: Fortran only: Error status (integer).
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.SH DESCRIPTION
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\fI\%MPI_Comm_set_name\fP allows a user to associate a name string with a
communicator. The character string that is passed to \fI\%MPI_Comm_set_name\fP
is saved inside the MPI library (so it can be freed by the caller
immediately after the call, or allocated on the stack). Leading spaces
in \fIname\fP are significant, but trailing ones are not.
.sp
\fI\%MPI_Comm_set_name\fP is a local (noncollective) operation, which affects
only the name of the communicator as seen in the process that made the
\fI\%MPI_Comm_set_name\fP call. There is no requirement that the same (or any)
name be assigned to a communicator in every process where it exists.
.sp
The length of the name that can be stored is limited to the value of
MPI_MAX_OBJECT_NAME in Fortran and MPI_MAX_OBJECT_NAME\-1 in C (to allow
for the null terminator). Attempts to set names longer than this will
result in truncation of the name. MPI_MAX_OBJECT_NAME must have a value
of at least 64.
.SH NOTES
.sp
Since \fI\%MPI_Comm_set_name\fP is provided to help debug code, it is sensible
to give the same name to a communicator in all of the processes where it
exists, to avoid confusion.
.sp
Regarding name length, under circumstances of store exhaustion, an
attempt to set a name of any length could fail; therefore, the value of
MPI_MAX_OBJECT_NAME should be viewed only as a strict upper bound on the
name length, not a guarantee that setting names of less than this length
will always succeed.
.SH ERRORS
.sp
Almost all MPI routines return an error value; C routines as the return result
of the function and Fortran routines in the last argument.
.sp
Before the error value is returned, the current MPI error handler associated
with the communication object (e.g., communicator, window, file) is called.
If no communication object is associated with the MPI call, then the call is
considered attached to MPI_COMM_SELF and will call the associated MPI error
handler. When MPI_COMM_SELF is not initialized (i.e., before
\fI\%MPI_Init\fP/\fI\%MPI_Init_thread\fP, after \fI\%MPI_Finalize\fP, or when using the Sessions
Model exclusively) the error raises the initial error handler. The initial
error handler can be changed by calling \fI\%MPI_Comm_set_errhandler\fP on
MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI
argument to mpiexec or info key to \fI\%MPI_Comm_spawn\fP/\fI\%MPI_Comm_spawn_multiple\fP\&.
If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN
error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error
handler is called for all other MPI functions.
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Open MPI includes three predefined error handlers that can be used:
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\fBMPI_ERRORS_ARE_FATAL\fP
Causes the program to abort all connected MPI processes.
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\fBMPI_ERRORS_ABORT\fP
An error handler that can be invoked on a communicator,
window, file, or session. When called on a communicator, it
acts as if \fI\%MPI_Abort\fP was called on that communicator. If
called on a window or file, acts as if \fI\%MPI_Abort\fP was called
on a communicator containing the group of processes in the
corresponding window or file. If called on a session,
aborts only the local process.
.IP \(bu 2
\fBMPI_ERRORS_RETURN\fP
Returns an error code to the application.
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MPI applications can also implement their own error handlers by calling:
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\fI\%MPI_Comm_create_errhandler\fP then \fI\%MPI_Comm_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_File_create_errhandler\fP then \fI\%MPI_File_set_errhandler\fP
.IP \(bu 2
\fI\%MPI_Session_create_errhandler\fP then \fI\%MPI_Session_set_errhandler\fP or at \fI\%MPI_Session_init\fP
.IP \(bu 2
\fI\%MPI_Win_create_errhandler\fP then \fI\%MPI_Win_set_errhandler\fP
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Note that MPI does not guarantee that an MPI program can continue past
an error.
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See the \fI\%MPI man page\fP for a full list of \fI\%MPI error codes\fP\&.
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See the Error Handling section of the MPI\-3.1 standard for
more information.
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\fBSEE ALSO:\fP
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.IP \(bu 2
\fI\%MPI_Comm_get_name\fP
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.SH COPYRIGHT
2003-2025, The Open MPI Community
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