MPI_T_event_get_source(3)

✨ MPI_T_event_get_source — the MPI manual, bestie edition ✨

okay so real talk, this page lives in the MPI manual section, and it's about one very specific little job: telling you where an event came from. that's it. that's the whole vibe. no cap. 🦋

---

🌸 NAME 🌸

MPI_T_event_get_source — returns the index of the source of the event instance 💅

like literally just hands you back the source index. nothing more, nothing less, and honestly? iconic for it.

---

✨ SYNOPSIS ✨

int MPI_T_event_get_source(MPI_T_event_instance event_instance,
                           int *source_index)

---

🎀 INPUT PARAMETERS 🎀

• event_instance — the event instance that got handed to the callback function (it's a handle, bestie, hold it gently 🫶)

---

💖 OUTPUT PARAMETERS 💖

• source_index — an integer index that identifies the source. that's the whole tea. 🍓

---

🧚 THREAD AND INTERRUPT SAFETY 🧚

okay so this routine is thread-safe, and that's a big deal in the best way. what that means fr fr: multiple threads can use this routine at the same time with zero user-provided thread locks needed. no mutexes, no stress, no drama. we love that for us. 💜

but — and this is the plot twist — it is NOT interrupt safe. 😭 typically that's because it uses memory allocation routines like malloc, or other non-MPICH runtime routines, and those routines are themselves not interrupt-safe. so yeah. not interrupt safe. noted. periodt.

---

🌈 ERRORS 🌈

so here's the thing about all MPI routines (except MPI_Wtime and MPI_Wtick, the two little exceptions 👑): they return an error value. in C routines it's the value of the function itself, and in Fortran routines it shows up in the last argument.

and before that value even comes back to you, the current MPI error handler gets called. by default, that error handler aborts the MPI job 💀 — yes, the whole thing, gone. you can change the error handler with:

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

there's also the MPI-1 routine MPI_Errhandler_set, which you can use, but its use is deprecated — so maybe don't, iykyk. 🙈

if you'd rather get error values returned instead of getting nuked, you can use the predefined error handler MPI_ERRORS_RETURN. also important: MPI does not guarantee that an MPI program can keep going after an error. however, MPI implementations will attempt to continue whenever possible. so like, they're trying their best. 🥺

here are the error codes this routine can throw at you:

• MPI_SUCCESS — no error; the MPI routine completed successfully. we ate. ✨
• MPI_T_ERR_INVALID — invalid use of the interface, or bad parameter value(s). 🚩
• MPI_T_ERR_INVALID_HANDLE — the handle is invalid. nope, not that one. 💀
• MPI_T_ERR_NOT_INITIALIZED — the MPI tool information interface is not initialized. you gotta turn it on first, bestie. 🔌
• MPI_ERR_OTHER — some other error; use MPI_Error_string to get more info about this error code. the vague one. the "it's giving mystery" one. 🕵️

---

heads up babe: that default error handler aborts the whole job, so if you're not vibing with that, set MPI_ERRORS_RETURN and go read your error codes like a grown-up. 🌸

---

okay that's the page!! go forth and get your event sources, you absolute legend 🫶💖

— this lil rewrite covers the MPI_T_event_get_source(3) page from the MPI manual, and the original shipped dated 4/10/2026. mwah, bye bestie!! 🎀🦋💅