MPI_REQUEST_C2F(3)

✨ NAME ✨

okay bestie, welcome to MPI_REQUEST_C2F(3), part of the Open MPI manual 💖 the whole glow-up here is handle translation — going from a C handle to a Fortran handle, or the other way around, and it's giving bilingual icon behavior 🌈

meet the whole squad of converters:

• 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

and yes babes, the missing MPI_Group_f2c / MPI_Group_c2f links are literally right there in the SYNTAX section, don't worry, we got her 👑

what do they all do? they translate a C handle into a Fortran handle, or vice versa. that's the whole vibe. periodt 💅

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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)

(no babes I did not typo MPI Fint and MPI Group in the Group lines, that's how the original rolls, we don't touch it, we respect the canon 🙈)

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🦋 DESCRIPTION 🦋

so here's the tea ☕ handles get passed between Fortran and C by using an explicit C wrapper to convert Fortran handles to C handles. and listen — there is no direct access to C handles in Fortran. none. zero. the door is locked, 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. slay 🎀

and the handle translation functions are provided in C to convert from a Fortran handle (which is an integer, yes really, an integer bestie) to a C handle, and vice versa. iconic behavior honestly ✨

🌸 example, because we love a concrete moment

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 (the Fortran value), then MPI_Comm_f2c returns a null C handle 🫥

and if comm is an invalid Fortran handle, then MPI_Comm_f2c returns an invalid C handle 💀 it's not gonna yell at you, it's just gonna hand you nonsense. vibe check failed fr fr

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💜 NOTE 💜

real talk, no cap: this function does not return an error value. so the result of calling it before MPI_Init or after MPI_Finalize is undefined. undefined!! that's the scary kind of undefined, not the cute kind 😭 call it at the right time or don't call it at all, bestie.

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👑 Copyright 👑

2003-2026, The Open MPI Community

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and that's the whole page, bestie 🫶 this was MPI_REQUEST_C2F(3) from the Open MPI manual, dated Sep 10, 2026 — go forth and translate those handles, you absolute main character 🧚💖 no cap.