MPI_Pready(3)

✨ MPI_Pready(3) ✨

okay bestie, welcome to the MPI_Pready page — this one lives in the MPI manual, section 3, and it is exactly as glam as it sounds 💅

🌸 NAME 🌸

MPI_Pready — Indicates that a given portion of the send buffer in a partitioned

no fr the NAME line really just trails off like that in the original, I'm not ghosting you, that's the whole line 🫶

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🎀 SYNOPSIS 🎀

int MPI_Pready(int partition, MPI_Request request)

🦋 INPUT PARAMETERS 🦋

• partition — the partition you're marking ready for transfer, and it's gotta be a non-negative integer ⭐
• request — the partitioned communication request (a handle, bestie, you know the vibe) 👑

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🧚 THREAD AND INTERRUPT SAFETY 🧚

okay so here's the tea ☕ — this routine is thread-safe. That means multiple threads can use it safely, and you do not need to bring your own user-provided thread locks. Slay, low maintenance queen 👑

But. It is not interrupt safe. 😭 Typically that's because it uses memory allocation routines like malloc, or other non-MPICH runtime routines that are themselves not interrupt-safe. So like… thread-safe? yes bestie. interrupt-safe? absolutely not, no cap 💀

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🌈 NOTES FOR FORTRAN 🌈

so if you're on your Fortran era: all MPI routines in Fortran (the only exceptions being MPI_WTIME and MPI_WTICK) get an extra argument called ierr tacked on at the end of the argument list. ierr is an integer and it means the exact same thing as the return value of the routine in C. Also, in Fortran, MPI routines are subroutines, and you invoke them with the call statement, periodt ✨

And heads up: all MPI objects (like MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran. iconic behavior, we accept it 💖

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💀 ERRORS 💀

Every MPI routine (except MPI_Wtime and MPI_Wtick) returns an error value — C routines as the value of the function, and Fortran routines in that last argument. And before that value comes back, the current MPI error handler gets called. By default, this error handler aborts the MPI job 😳 so like, yeah, it's giving dramatic.

You can swap the error handler out with:

• 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, but its use is deprecated 🙈 (we don't do that anymore, bestie). 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's giving "we'll try our best" energy 🥺

⭐ Error Codes ⭐

• MPI_SUCCESS — No error; MPI routine completed successfully. we love a happy ending 🫶
• MPI_ERR_REQUEST — Invalid MPI_Request. Either null or, in the case of a MPI_Start or MPI_Startall, not a persistent request. 🚩
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code. the mystery box of errors 🎁

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and that's the whole page, bestie!! this was MPI_Pready(3) from the MPI manual, dated 4/10/2026 — go mark those partitions ready and have the day you deserve 💜🦋✨