MPI_REQUEST_C2F(3)

💅 MPI_REQUEST_C2F(3) — bestie edition ✨

okay so this one's from Open MPI, and it's the whole little family of handle-translation girlies 🫶

MPI_Comm_f2c, MPI_Comm_c2f, MPI_File_f2c, MPI_File_c2f, MPI_Info_f2c, MPI_Info_c2f, MPI_Message_f2c, MPI_Message_c2f, MPI_Op_f2c, MPI_Op_c2f, MPI_Request_f2c, MPI_Request_c2f, MPI_Type_f2c, MPI_Type_c2f, MPI_Win_f2c, MPI_Win_c2f — literally just translates a C handle into a Fortran handle, or vice versa. that's the whole job. iconic of them honestly 💅

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✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

MPI_Comm MPI_Comm_f2c(MPI_Fint comm)
MPI_Fint MPI_Comm_c2f(MPI_Comm comm)

MPI_File MPI_File_f2c(MPI_Fint file)
MPI_Fint MPI_File_c2f(MPI_File file)

MPI_Group MPI_Group_f2c(MPI Fint group)
MPI_Fint MPI_Group_c2f(MPI Group group)

MPI_Info MPI_Info_f2c(MPI_Fint info)
MPI_Fint MPI_Info_c2f(MPI_Info info)

MPI_Message MPI_Message_f2c(MPI_Fint message)
MPI_Fint MPI_Message_c2f(MPI_Message message)

MPI_Op MPI_Op_f2c(MPI_Fint op)
MPI_Fint MPI_Op_c2f(MPI_Op op)

MPI_Request MPI_Request_f2c(MPI_Fint request)
MPI_Fint MPI_Request_c2f(MPI_Request request)

MPI_Datatype MPI_Type_f2c(MPI_Fint datatype)
MPI_Fint MPI_Type_c2f(MPI_Datatype datatype)

MPI_Win MPI_Win_f2c(MPI_Fint win)
MPI_Fint MPI_Win_c2f(MPI_Win win)

(yes bestie, <pink>MPI Fint group</pink> and <pink>MPI Group group</pink> really do have spaces up there instead of underscores — that's how they're written in the original, so I'm keeping them exactly as-is, no editing, no "fixing", periodt 🙈)

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🦋 DESCRIPTION 🦋

so the whole vibe: handles get passed between Fortran and C by using an explicit C wrapper to convert Fortran handles to C handles. there is no direct access to C handles in Fortran — none, zero, don't even try it 💀

The type definition MPI_Fint is provided in C for an integer of the size that matches a Fortran INTEGER; usually, MPI_Fint will be equivalent to int. cute little bridge type, love that for us 🎀

The handle translation functions are provided in C to convert from a Fortran handle (which is an integer) to a C handle, and vice versa. lowkey the whole point of this page ngl.

For example, if comm is a valid Fortran handle to a communicator, then MPI_Comm_f2c returns a valid C handle to that same communicator; if comm = MPI_COMM_NULL (Fortran value), then MPI_Comm_f2c returns a null C handle; if comm is an invalid Fortran handle, then MPI_Comm_f2c returns an invalid C handle. like, it does not gatekeep, it does not validate, it just vibes and hands you back what you gave it 🫶

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💜 NOTE 💜

This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined 😭 so pls call it at a reasonable time, bestie. main character energy does not protect you from undefined behavior fr fr.

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the page, babes ⭐ — brought to you by Open MPI, dated Sep 11, 2026, filed under MPI_REQUEST_C2F(3) 🦋🎀💖 slay responsibly ✨