MPI_Info_get_string(3)

💖 MPI_Info_get_string(3) 💖

okay bestie, welcome to the MPI manual, bestie. yes it's that MPI — the Message Passing Interface one, the group chat for your CPU cores 💅. this page is all about MPI_Info_get_string, and no cap, it's a little cutie: you hand it a key, it hands you back the value. mic drop, that's the whole job.

It lives in section 3 of the MPI manual, so you already know it's a library routine and not some shell command you type at 3am. 🦋

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✨ NAME ✨

MPI_Info_get_string — Retrieves the value associated with a key 💖

yes literally that. glow-up for your info object. it reads a value out and hands it to you. obsessed.

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✨ SYNOPSIS ✨

int MPI_Info_get_string(MPI_Info info, const char *key, int *buflen,
       char *value, int *flag)

that's the exact signature girlies, do not freestyle it, do not "fix" it, copy it character for character 🙈

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🌸 INPUT PARAMETERS 🌸

• info — the info object, a handle. that's your little bag of key/value pairs 🎀
• key — the key, a string. the thing you're looking up in the bag ✨

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🦋 INPUT/OUTPUT PARAMETERS 🦋

• buflen — length of buffer, an integer. you bring the size, it's in and out — so it's giving both ways, main character energy fr fr

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💅 OUTPUT PARAMETERS 💅

• value — the value, a string. the payoff!! the content!! the moment 🫶
• flag — a boolean: true if the key is defined, false if it's not. it's literally doing a vibe check on your key 👑

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🧚 THREAD AND INTERRUPT SAFETY 🧚

okay so: this routine is thread-safe. that means multiple threads can use it at the same time and nobody needs to hand-write their own thread locks. slay, no drama, no locks, we love to see it 🌈

but bestie. it is NOT interrupt safe. 😭 typically that's because it uses memory allocation routines like malloc, or other non-MPICH runtime routines that themselves aren't interrupt-safe. so don't be sending signals at it mid-chomp, okay? respect the boundary.

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💜 NOTES FOR FORTRAN 💜

all MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an extra argument ierr sitting at the end of the argument list. ierr is an integer and it means exactly the same thing as the return value of the routine in C. no difference, no plot twist ✨

and in Fortran, MPI routines are subroutines, invoked with the call statement. yes, call, that's the word, lowercase gang 💅

also: all MPI objects (like MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. that's the whole tea. ☕

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💀 ERRORS 💀

every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value — C routines return it as the value of the function, and Fortran routines put it in that last argument. before that value comes back, the current MPI error handler gets called. and by default? bestie, that error handler aborts the MPI job. like, it's over. 🪦

you can change the error handler though:

• MPI_Comm_set_errhandler — for communicators
• MPI_File_set_errhandler — for files
• MPI_Win_set_errhandler — for RMA windows

the MPI-1 routine MPI_Errhandler_set may be used too, but ngl its use is deprecated. it's giving retired. don't build your whole personality on it 🙈

the predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned instead. note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. so it might survive. it might not. we don't know her 🫠

the error codes themselves:

• MPI_SUCCESS — no error; MPI routine completed successfully. the good ending ⭐
• MPI_ERR_ARG — invalid argument. some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK). it's giving "one of these is not like the others" 😭
• MPI_ERR_INFO — invalid Info 💀
• MPI_ERR_OTHER — other error; use MPI_Error_string to get more information about this error code. the catch-all, the "and friends", the miscellaneous bin 🎀

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🌟 SEE ALSO? 🌟

okay so this page as printed doesn't hand us a SEE ALSO list, and I'm not about to invent references that aren't there — that would be lying and we don't do that in this group chat. the cross-references that DO show up above are the ones you already met: MPI_Comm_set_errhandler, MPI_File_set_errhandler, MPI_Win_set_errhandler, MPI_Errhandler_set, MPI_ERRORS_RETURN, MPI_Error_string, MPI_Wtime, MPI_Wtick, MPI_WTIME, and MPI_WTICK. go say hi to them 💖

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and that's the whole page bestie 💅 tysm for reading, this was MPI_Info_get_string(3), dated 4/10/2026, from the MPI manual — stay hydrated, free your buffers, and go get that value. periodt. 🎀🦋✨💖