MPI_COMM_GET_NAME(3)

✨ MPI_COMM_GET_NAME(3) ✨

okay so this is the Open MPI girlies' guide to MPI_Comm_get_name — and bestie, it does exactly what it says on the tin: it hands you back the name that was most recently associated with a communicator. that's it. that's the whole vibe. 💅

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🌸 NAME 🌸

MPI_Comm_get_name — returns the name that was most recently associated with a communicator. lowkey iconic of her.

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🎀 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

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⭐ INPUT PARAMETER ⭐

• comm — the communicator whose name you're asking about, i.e. the handle. like sliding into her DMs to ask what her name is 🫶

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🌈 OUTPUT PARAMETER 🌈

• comm_name — the name previously stored on the communicator, or an empty string if no such name exists (string). she might be nameless, it's fine, no judgement 💀
• resultlen — length of the returned name (integer). yes, you get the character count too, we're thorough.
• ierror — Fortran only: error status (integer). classic Fortran, always gotta have the last word 🙈

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💜 DESCRIPTION 💜

so MPI_Comm_get_name returns the last name that was previously associated with the given communicator. and the way that names are language-agnostic?? obsessed. the name may be set and retrieved from any language, and the same name will come back to you no matter which language you used to ask. multilingual queen 👑

comm_name should be allocated so that it can hold a resulting string of length MPI_MAX_OBJECT_NAME characters — do not skimp on the buffer bestie, she will not fit otherwise. 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). no cap, that's just how she is.

the three predefined communicators will have predefined names associated with them — so 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. yes the name is the same as the thing, it's giving "my name is my name" energy and honestly? valid. ✨

and 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. rebranding era, we love to see it 💅

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🍓 NOTES 🍓

it is safe to simply print the string returned by MPI_Comm_get_name, because it is always a valid string even if there was no name. so go ahead, printf her, she won't embarrass you 🫶

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. so it costs you memory, but it buys you clarity. therefore, there is no requirement that users use these functions to associate names with communicators. however — and this is the good part — 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. iykyk: named communicators = readable traces = main character debugging energy 🔥

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💀 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. (yes, the ierror girlie again.)

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_thread, after 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 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_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. dramatic? yes. effective? also yes 😭
• 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 was called on that communicator. if called on a window or file, it acts as if 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. situational awareness queen 👑
• MPI_ERRORS_RETURN — returns an error code to the application. the chill one. hands you the L and lets you deal with it 💅

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

• MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
• MPI_File_create_errhandler then MPI_File_set_errhandler
• MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
• MPI_Win_create_errhandler then MPI_Win_set_errhandler

note that MPI does not guarantee that an MPI program can continue past an error. fr fr, an error might just be the end of the road 🪦

see the MPI man page for a full list of MPI error codes.

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

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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💌 and that's the whole page bestie — go forth, name your communicators, and let your profiler live its best, least-cryptic life. slay. 🦋✨

with love, the Open MPI girlies 💖 — page dated Sep 11, 2026, MPI_COMM_GET_NAME(3), from the Open MPI crew (2003-2026, The Open MPI Community). mwah. 🎀