MPI_INFO_F2C(3)

💅 MPI_INFO_F2C(3) — the Open MPI glow-up 🦋

okay bestie, so this is one of those pages from the Open MPI manual that's basically a whole friend group of functions all sharing one page, and they're all about the same thing: translating handles between C and Fortran. no cap. sixteen functions, one vibe.

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✨ NAME ✨

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 — Translates a C handle into a Fortran handle, or vice versa. 🫶

like, it's a two-way translator. that's the whole assignment. 💅

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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, we're copying these exactly — including the MPI Fint group / MPI Group group situation in the Group pair. that's how it's written in the source, and your girl does not edit the source. 🫡)

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🎀 DESCRIPTION 🎀

okay 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. that's the whole mechanism. there is no direct access to C handles in Fortran, periodt. 🙅‍♀️

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. (usually!! not always!! read the room 😭)

and the handle translation functions? they're provided in C to convert from a Fortran handle (which is an integer) to a C handle, and vice versa. it's giving glow-up-and-down. ✨

for example — and this is the iconic example, bestie — if comm is a valid Fortran handle to a communicator, then MPI_Comm_f2c returns a valid C handle to that same communicator. slay. 💅

• 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's not gonna fix your problems, it's just gonna translate them fr fr.

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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 like… no error code, no little safety net, nothing. if you call it before MPI_Init or after MPI_Finalize, you are in the undefined behaviour zone and honestly that's on you, bestie 😭🙈. main character energy only after MPI_Init.

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the whole page, bestie 🌈💜 — brought to you by the fine folks at Open MPI, page dated Sep 11, 2026, version vibes intact, facts untouched, only the aesthetic got a glow-up. 🎀✨ you're welcome, go translate some handles. 🦋