MPI_COMM_REMOTE_GROUP(3)

💖 MPI_COMM_REMOTE_GROUP 💖

okay bestie, sit down, hydrate, because today we're reading the Open MPI manual page for MPI_Comm_remote_group, and it's literally the little accessor that could. 🫶

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✨ NAME ✨

MPI_Comm_remote_group — Accesses the remote group associated with an intercommunicator.

like. that's it. that's the job. and she does it flawlessly. 👑

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🌸 SYNTAX 🌸

🎀 C Syntax

#include <mpi.h>

int MPI_Comm_remote_group(MPI_Comm comm, MPI_Group *group)

🎀 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMM_REMOTE_GROUP(COMM, GROUP, IERROR)
     INTEGER COMM, GROUP, IERROR

🎀 Fortran 2008 Syntax

USE mpi_f08
MPI_Comm_remote_group(comm, group, ierror)
     TYPE(MPI_Comm), INTENT(IN) :: comm
     TYPE(MPI_Group), INTENT(OUT) :: group
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

lowkey obsessed with how mpi_f08 just said "types? yes. optional error? also yes." 💅

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🧚 INPUT PARAMETER 🧚

• comm — Communicator. that's the whole description bestie, she's a giver, she's not gonna over-explain. 💖

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🦋 OUTPUT PARAMETERS 🦋

• group — Remote group of communicator. 🎀
• ierror — Fortran only: Error status (integer).

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🌈 DESCRIPTION 🌈

MPI_Comm_remote_group accesses the remote group associated with an intercommunicator.

The intercommunicator accessors (MPI_Comm_test_inter, MPI_Comm_remote_size, MPI_Comm_remote_group) are all local operations.

not a single byte of network traffic. no cap. they're all just vibing locally. ✨

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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.

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. 😭 everybody's going down together, it's giving group project energy.
• 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, 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.
• MPI_ERRORS_RETURN — Returns an error code to the application. the polite one. 🎀

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, read that last line twice. an error is NOT a "we'll figure it out later" situation. 💀

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.

See also:

• MPI_Comm_test_inter
• MPI_Comm_remote_size
• MPI_Intercomm_create
• MPI_Intercomm_merge

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👑 Copyright 👑

2003-2026, The Open MPI Community

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and that's the whole page, bestie!! 🌸 the manual name up top is MPI_COMM_REMOTE_GROUP(3), she lives in Open MPI, and this lil edition is dated Sep 10, 2026. go forth and access those remote groups, you absolute icon. 💖✨🦋💅