MPI_COMM_SET_NAME(3)				     Open MPI				      MPI_COMM_SET_NAME(3)

MPI_Comm_set_name — Associates a name with a communicator.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Comm_set_name(MPI_Comm comm, const char *comm_name)

   Fortran Syntax
	  USE MPI
	  ! or the older form: INCLUDE 'mpif.h'
	  MPI_COMM_SET_NAME(COMM, COMM_NAME, IERROR)
	       INTEGER COMM, IERROR
	       CHARACTER*(*) COMM_NAME

   Fortran 2008 Syntax
	  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

INPUT/OUTPUT PARAMETER
       • comm: Communicator whose identifier is to be set (handle).

INPUT PARAMETER
       • comm_name: Character string to be used as the identifier for the communicator (string).

OUTPUT PARAMETER
       • ierror: Fortran only: Error status (integer).

DESCRIPTION
       MPI_Comm_set_name  allows  a user to associate a name string with a communicator. The character string that
       is passed to MPI_Comm_set_name 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 name are significant, but
       trailing ones are not.

       MPI_Comm_set_name is a local (noncollective) operation, which affects only the name of the communicator	as
       seen  in	 the  process that made the MPI_Comm_set_name call. There is no requirement that the same (or any)
       name be assigned to a communicator in every process where it exists.

       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.

NOTES
       Since MPI_Comm_set_name 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.

       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.

ERRORS
       Almost  all MPI routines return an error value; C routines as the return result of the function and Fortran
       routines in the last argument.

       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 MPI_Init <#mpi-init>/MPI_Init_thread <#mpi-init-thread>,
       after MPI_Finalize <#mpi-finalize>, or when using the Sessions Model  exclusively)  the	error  raises  the
       initial	error  handler.	 The  initial  error  handler can be changed by calling MPI_Comm_set_errhandler <#
       mpi-comm-set-errhandler> on MPI_COMM_SELF when using the World model,  or  the  mpi_initial_errhandler  CLI
       argument	  to   mpiexec	 or   info  key	 to  MPI_Comm_spawn  <#mpi-comm-spawn>/MPI_Comm_spawn_multiple	<#
       mpi-comm-spawn-multiple>.  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.

       Open MPI includes three predefined error handlers that can be used:

       • MPI_ERRORS_ARE_FATAL Causes the program to abort all connected MPI processes.

       • MPI_ERRORS_ABORT An error handler that can be invoked on a communicator, window, file, or  session.  When
	 called on a communicator, it acts as if MPI_Abort <#mpi-abort> was called on that communicator. If called
	 on  a window or file, acts as if MPI_Abort <#mpi-abort> 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.

       • MPI_ERRORS_RETURN Returns an error code to the application.

       MPI applications can also implement their own error handlers by calling:

       • MPI_Comm_create_errhandler	<#mpi-comm-create-errhandler>	  then	   MPI_Comm_set_errhandler	<#
	 mpi-comm-set-errhandler>

       • MPI_File_create_errhandler	 <#mpi-file-create-errhandler>	   then	    MPI_File_set_errhandler	<#
	 mpi-file-set-errhandler>

       • MPI_Session_create_errhandler	 <#mpi-session-create-errhandler>   then   MPI_Session_set_errhandler	<#
	 mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>

       • MPI_Win_create_errhandler	<#mpi-win-create-errhandler>	  then	    MPI_Win_set_errhandler	<#
	 mpi-win-set-errhandler>

       Note that MPI does not guarantee that an MPI program can continue past an error.

       See the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

       See the Error Handling section of the MPI-3.1 standard for more information.

       See also:

	  • MPI_Comm_get_name <#mpi-comm-get-name>

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				      MPI_COMM_SET_NAME(3)
