MPI_COMM_DUP_WITH_INFO(3)

💅 MPI_COMM_DUP_WITH_INFO(3) — like, the Open MPI glow-up of a communicator ✨

okay bestie, so this is a page from the Open MPI manual set, and today's main character is MPI_Comm_dup_with_info — it duplicates an existing communicator using provided info. yes, you heard me. a whole communicator. duplicated. with your info attached. slay 🎀

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✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Comm_dup_with_info(MPI_Comm comm, MPI_Info info, MPI_Comm *newcomm)

🌸 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_COMM_DUP_WITH_INFO(COMM, INFO, NEWCOMM, IERROR)
    INTEGER COMM, INFO, NEWCOMM, IERROR

🌸 Fortran 2008 Syntax

USE mpi_f08

MPI_Comm_dup_with_info(comm, info, newcomm, ierror)
    TYPE(MPI_Comm), INTENT(IN) :: comm
    TYPE(MPI_Info), INTENT(IN) :: info
    TYPE(MPI_Comm), INTENT(OUT) :: newcomm
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🦋 INPUT PARAMETER 🦋

• comm — the communicator, bestie. it's a handle. 💖
• info — the info argument. also a handle. it's giving "extra instructions." ✨

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👑 OUTPUT PARAMETERS 👑

• newcomm — a copy of comm (handle). your shiny new communicator, fresh out of the box 🎁
• ierror — Fortran only: error status (integer). classic Fortran behavior, love that for us 💅

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🌈 DESCRIPTION 🌈

okay so here's the tea: MPI_Comm_dup_with_info acts exactly like MPI_Comm_dup — like, identical energy — except that the info hints associated with the communicator comm are not duplicated in newcomm. nope, not coming along for the ride 🙈

instead, the hints provided by the argument info are associated with the output communicator newcomm. so it's a swap, not a copy. iconic behavior honestly.

for the list of recognized info keys, go peek at MPI_Comm_set_info — that's where the menu lives 🍓

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💀 NOTES 💀

so like, why do we do this? this operation is used to provide a parallel library call with a duplicate communication space that has the same properties as the original communicator. same properties, bestie. that includes:

• any attributes (see below 👀)
• topologies (see the "Process Topologies" chapter in the MPI Standard)

and here's the cool part — this call is valid even if there are pending point-to-point communications involving the communicator comm. like, no cap, you can have messages in flight and it still works 🔥

a typical call might involve an MPI_Comm_dup_with_info at the beginning of the parallel call, and an MPI_Comm_free of that duplicated communicator at the end of the call. bookends, honestly. other models of communicator management are also possible — you do you 💜

this call applies to both intra- and intercommunicators. inclusive king behavior 👑

⚠️ so this is the serious bit, listen up: it is not defined by the MPI standard what happens if the attribute copy callback invokes other MPI functions. and in Open MPI specifically, it is not valid for attribute copy callbacks (or any of their children) to add or delete attributes on the same object on which the attribute copy callback is being invoked. like, do not do that. fr fr. 💀

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😭 ERRORS 😭

almost all MPI routines return an error value — C routines give it back as the return result of the function, and Fortran routines put it in the last argument. classic.

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. and 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 an info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. and 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.

✨ the three predefined error handlers ✨

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

• MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. all of them. everyone. gone 💀
• 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, it aborts only the local process. 💅
• MPI_ERRORS_RETURN — returns an error code to the application. polite. respectful. hands you the problem and lets you deal 🙈

🌸 DIY error handlers 🌸

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. like, it might just be over. 😭

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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🫶 SEE ALSO 🫶

• MPI_Comm_dup — the original, the blueprint, the blueprint's blueprint ✨

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🎀 COPYRIGHT 🎀

2003-2026, The Open MPI Community</purl>

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and that's the whole page bestie!! 💖 written by the Open MPI girlies, dated Sep 11, 2026, and catalogued under MPI_COMM_DUP_WITH_INFO(3) — go forth and duplicate responsibly 🦋✨👑