MPI_WIN_C2F(3)

💅 MPI_WIN_C2F(3) — Open MPI 💅

okay bestie, welcome to the Open MPI manual page for MPI_WIN_C2F(3). this is the group-chat explainer for translating C handles into Fortran handles, or the other way around. no cap, it's all about the f2c / c2f besties. 🫶

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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. ✨

also, the syntax block down there has the MPI_Group_f2c and MPI_Group_c2f pair too — yes, literally, keep scrolling. 🦋

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✨ SYNTAX ✨

💻 C Syntax 💻

verbatim code, periodt — including the itty-bitty spaces in the Group lines, so don't come for me bestie:

#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)

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🌸 DESCRIPTION 🌸

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's just the rule, 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. iconic little type matchmaking moment. 🎀

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. like a little handle glow-up in both directions. ✨

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

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💀 NOTE 💀

🚨 bestie, warning: this function does not return an error value. consequently, the result of calling it before MPI_Init or after MPI_Finalize is undefined. like, do not do that. undefined behavior is not a vibe. 💀😭

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👑 COPYRIGHT 👑

mwah 💋 this page is part of Open MPI, © 2003-2026, The Open MPI Community, and the date on this one is Sep 11, 2026. bye bestie, go translate those handles! 🎀✨🫶