MPI_COMM_GET_NAME(3)				     Open MPI				      MPI_COMM_GET_NAME(3)

MPI_Comm_get_name — Returns the name that was most recently associated with a communicator.

SYNTAX
   C Syntax
	  #include <mpi.h>

	  int MPI_Comm_get_name(MPI_Comm comm, char *comm_name, int *resultlen)

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

   Fortran 2008 Syntax
	  USE mpi_f08
	  MPI_Comm_get_name(comm, comm_name, resultlen, ierror)
	       TYPE(MPI_Comm), INTENT(IN) :: comm
	       CHARACTER(LEN=MPI_MAX_OBJECT_NAME), INTENT(OUT) :: comm_name
	       INTEGER, INTENT(OUT) :: resultlen
	       INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETER
       • comm: Communicator the name of which is to be returned (handle).

OUTPUT PARAMETER
       • comm_name:  Name  previously  stored  on  the	communicator,  or  an  empty string if no such name exists
	 (string).

       • resultlen: Length of returned name (integer).

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

DESCRIPTION
       MPI_Comm_get_name returns the last name that was previously associated with  the	 given	communicator.  The
       name may be set and retrieved from any language. The same name will be returned independent of the language
       used.  comm_name	 should	 be allocated so that it can hold a resulting string of length MPI_MAX_OBJECT_NAME
       characters. MPI_Comm_get_name returns a copy of the set name in comm_name.

       If the user has not associated a name with a communicator,  or  an  error  occurs,  MPI_Comm_get_name  will
       return  an  empty  string  (all	spaces	in Fortran, “” in C). The three predefined communicators will have
       predefined  names  associated  with  them.  Thus,  the  names   of   MPI_COMM_WORLD,   MPI_COMM_SELF,   and
       MPI_COMM_PARENT	will have the default of MPI_COMM_WORLD, MPI_COMM_SELF, and MPI_COMM_PARENT. The fact that
       the system may have chosen to give a default name to a communicator does not prevent the user from  setting
       a name on the same communicator; doing this removes the old name and assigns the new one.

NOTES
       It is safe simply to print the string returned by MPI_Comm_get_name, as it is always a valid string even if
       there was no name.

       Note that associating a name with a communicator has no effect on the semantics of an MPI program, and will
       (necessarily)  increase	the  store  requirement	 of the program, since the names must be saved. Therefore,
       there is no requirement that users use these functions  to  associate  names  with  communicators.  However
       debugging  and  profiling  MPI  applications may be made easier if names are associated with communicators,
       since the debugger or profiler should then be able to present information in a less cryptic manner.

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.

Copyright
       2003-2026, The Open MPI Community

						   Mar 05, 2026				      MPI_COMM_GET_NAME(3)
