MPI_COMM_REMOTE_SIZE(3)

MPI_COMM_REMOTE_SIZE(3) — Open MPI manual 💖

okay so bestie, you're looking at the MPI_COMM_REMOTE_SIZE(3) page from the Open MPI manual — manual name folded in right at the top, cute and efficient, periodt. 💅

🌸 NAME 🌸

MPI_Comm_remote_size — determines the size of the remote group associated with an intercommunicator. literally what it says on the tin, no cap. ✨

✨ SYNTAX ✨

💻 C Syntax 💻

#include <mpi.h>

int MPI_Comm_remote_size(MPI_Comm comm, int *size)

🧚 Fortran Syntax 🧚

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

🦋 Fortran 2008 Syntax 🦋

USE mpi_f08
MPI_Comm_remote_size(comm, size, ierror)
     TYPE(MPI_Comm), INTENT(IN) :: comm
     INTEGER, INTENT(OUT) :: size
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🫶 INPUT PARAMETER 🫶

• comm — Communicator (handle). that's the handle you're handing over, bestie. 💅

🎀 OUTPUT PARAMETERS 🎀

• size — Number of processes in the remote group of comm (integer). so like, how many besties are over there in the remote group. 👑
• ierror — Fortran only: Error status (integer). Fortran girlies get this one in the last argument. 🫶

💖 DESCRIPTION 💖

MPI_Comm_remote_size determines the size of the remote group associated with an intercommunicator. that's the whole assignment, and it ate. ✨

The intercommunicator accessors (MPI_Comm_test_inter, MPI_Comm_remote_size, MPI_Comm_remote_group) are all local operations. yes, all three are local — lowkey iconic, fr fr. 🦋

💅 ERRORS 💅

Almost all MPI routines return an error value; C routines get it as the return result of the function and Fortran routines get it in the last argument. bestie, that's just how the error value arrives. 😭

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. 💀
• 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. 🫶

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, pls don't assume it can keep going after an error, okay? 😬

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_group
• MPI_Intercomm_create
• MPI_Intercomm_merge

🎀 COPYRIGHT 🎀

2003-2026, The Open MPI Community

💌 okay bye bestie — this MPI_COMM_REMOTE_SIZE(3) page is from Open MPI, footer date Sep 11, 2026. mwah! 💋