MPI_Pready_list(3)

✨ MPI_Pready_list(3) ✨ — it's giving "yes bestie, these portions are READY" 💅

okay so real talk, this is a page from the MPI manual (section 3, the library-call girlies 🎀), and today we're talking about MPI_Pready_list.

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💖 NAME 💖

MPI_Pready_list — Indicates that a list of portions of the send buffer in a partitioned

(that's the actual sentence, she's a little unfinished, we love her anyway 🫶)

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🌸 SYNOPSIS 🌸

int MPI_Pready_list(int length, const int array_of_partitions[],
MPI_Request request)

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🦋 INPUT PARAMETERS 🦋

• length — list length (integer)
• array_of_partitions — array of partitions (non-negative integer)
• request — partitioned communication request (handle)

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🔥 THREAD AND INTERRUPT SAFETY 🔥

Good news bestie: this routine is thread-safe. What that means is you can literally call it from multiple threads at the same time and you do not need to bring your own thread locks — she handles herself. 💅

But. However. The routine is not interrupt safe. Not me being the bearer of bad news 😭 — typically this is because of memory allocation routines like malloc, or other non-MPICH runtime routines, which are themselves not interrupt-safe. So like, respect the boundary, okay?

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🌈 NOTES FOR FORTRAN 🌈

Okay so Fortran girlies, listen up, this is important:

All MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr at the end of the argument list. ierr is an integer and has the same meaning as the return value of the routine in C. In Fortran, MPI routines are subroutines, and they're invoked with the call statement.

All MPI objects (e.g., MPI_Datatype, MPI_Comm) are of type INTEGER in Fortran.

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😭 ERRORS 😭

Every single MPI routine (except MPI_Wtime and MPI_Wtick, the main characters who don't play that game) returns an error value: C routines as the value of the function, and Fortran routines in the last argument. Before the value is returned, the current MPI error handler gets called. By default, this error handler aborts the MPI job. 💀

The error handler may be changed with MPI_Comm_set_errhandler (for communicators), MPI_File_set_errhandler (for files), and MPI_Win_set_errhandler (for RMA windows). The MPI-1 routine MPI_Errhandler_set may be used but its use is deprecated (she's old, let her rest 🙈).

The predefined error handler MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not guarantee that an MPI program can continue past an error; however, MPI implementations will attempt to continue whenever possible. Slay? Kind of? 🫶

• MPI_SUCCESS — No error; MPI routine completed successfully. ✨ (the only one we like)
• MPI_ERR_ARG — Invalid argument. Some argument is invalid and is not identified by a specific error class (e.g., MPI_ERR_RANK).
• 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.

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🌟 reminder from your girl: partitioned communication is iconic, MPI_Pready_list is iconic, and you marking a list of portions ready all at once is main character energy. periodt. 👑

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and that's the page bestie!! this one's from the MPI manual, version date 4/10/2026 — that's MPI_Pready_list(3), and honestly she ate. 😌💖 bye!! 🎀