MPI_TYPE_C2F(3)

💅 MPI_TYPE_C2F(3) 💅

okay bestie, welcome to the Open MPI glow-up of this page — it's the handle-translation one, and it's honestly so useful it hurts. 🫶

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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 — literally all of them translate a C handle into a Fortran handle, or vice versa. 🔁 (f2c = Fortran → C, c2f = C → Fortran, iykyk)

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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)

🫶 ngl bestie, that block is copied character for character from the page — yes, even the MPI Fint / MPI Group bits in the group pair. Type it exactly like that, don't @ me, that's the vibe check. 💀

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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. There is literally 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. (she's lowkey just int in a cute outfit 💅)

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. two-way street, iconic behavior. 🚦

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. ✨ match the energy, get the handle ✨

🌈 bestie the symmetry here is giving main character energy: good in → good out, null in → null out, chaos in → chaos out. she's not judging, she's just reflecting. 🪞

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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, undefined undefined. no error code to catch, no warning, nothing — she just does whatever. do NOT call her before MPI_Init, do NOT call her after MPI_Finalize, fr fr. 🙈

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👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

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and that's the whole page, bestie — no cap, every flag-shaped detail and every handle accounted for. 💖

🌸 mwah 💋 — with love from the Open MPI girlies, dated Sep 11, 2026, © 2003-2026, The Open MPI Community. go translate some handles and slay. 🎀✨🦋