MPI_FILE_F2C(3)

💖 MPI_FILE_F2C(3) 💖

okay bestie, welcome to the Open MPI manual page for the whole handle-translation friend group. This is the MPI_FILE_F2C(3) page, and its whole thing is translating a C handle into a Fortran handle, or vice versa — no cap. The headline squad is:

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 — all doing the translate-y thing. 💅

And yes, the MPI_Group_f2c / MPI_Group_c2f duo is also in the syntax section below, living its best life. 🦋

✨ 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 tea: 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 — that door is locked, bestie. 🔒

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 bilingual handle energy. 🌈

Example time, because examples are iconic: 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. That's the whole vibe check. ✨

🍓 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, do not do that, bestie — it's not a cute look. 😭

👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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💖 big kiss and bestie energy: this page is from Open MPI, dated Sep 11, 2026, and it's the MPI_FILE_F2C(3) manual page. Slay. 💖