MPI_FILE_C2F(3)

💅 MPI_FILE_C2F(3) 💅

Open MPI manual, bestie — welcome to the handle-translation page, it's lowkey iconic 🫶

🌸 NAME 🌸

Okay so this page is the whole crossover episode: 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, and MPI_Win_c2f — they translate a C handle into a Fortran handle, or vice versa. Periodt 💖

The way this list is just pure handle-translation energy? Obsessed, no cap.

✨ 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)

🦋 DESCRIPTION 🦋

Okay so here's the vibe: handles are 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 — not me making that up, that's literally the rule 🙈.

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. 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. It's giving bridge between two worlds 🌈.

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. Valid, null, invalid — all three cases, bestie, fr fr 💅.

💀 NOTE 💀

This function does not return an error value. Consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined. Like, literally undefined — do not test the universe on this one 😭.

👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

xoxo, your Open MPI bestie 💖 — page MPI_FILE_C2F(3), dated Sep 11, 2026 🎀