MPI_File_write_all(3)

💖 MPI_File_write_all(3) 💖

okay bestie, welcome to the MPI_File_write_all page — it lives in the MPI manual section 3, and it's literally the collective file-write glow-up you've been waiting for 🦋

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✨ NAME ✨

MPI_File_write_all — collective write using individual file pointer 🫶

(collective!! everyone's in on it!! no sneaky solo writes here 💅)

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✨ SYNOPSIS ✨

int MPI_File_write_all(MPI_File fh, const void *buf, int count,
MPI_Datatype datatype, MPI_Status *status)

int MPI_File_write_all_c(MPI_File fh, const void *buf, MPI_Count count,
MPI_Datatype datatype, MPI_Status *status)

two icons, one job. the _c variant is the one with the big-girl MPI_Count type for count, periodt ✨

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✨ INPUT PARAMETERS ✨

• fh — file handle (handle) 🎀 your lil ticket to the file, hold it tight
• buf — initial address of buffer (choice) 💖 where the data's living before it heads out
• count — number of elements in buffer (integer) 🔢 how many of them there are
• datatype — datatype of each buffer element (handle) 🌸 what kind of thing each element is

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✨ OUTPUT PARAMETERS ✨

• status — status object (Status) 📋 it comes back with the receipts

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✨ THREAD AND INTERRUPT SAFETY ✨

okay so 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. no cap.

BUT — and this is the plot twist 😭 — the routine is not interrupt safe. typically that's because of memory allocation routines like malloc or other non-MPICH runtime routines that are themselves not interrupt-safe. so like, threads: yes bestie. interrupts: absolutely not. 🙈

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✨ NOTES FOR FORTRAN ✨

all MPI routines in Fortran (except for MPI_WTIME and MPI_WTICK) have an additional argument ierr chillin' 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. that's just the Fortran lore, iykyk 🧚

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✨ ERRORS ✨

all MPI routines (except MPI_Wtime and MPI_Wtick) return 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 is called. by default, this error handler aborts the MPI job 💀 (yes, dramatic). 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 🚫. 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 🫶

• MPI_SUCCESS — No error; MPI routine completed successfully. 👑 the dream
• 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_BUFFER — Invalid buffer pointer. Usually a null buffer where one is not valid. 😭
• MPI_ERR_COUNT — Invalid count argument. Count arguments must be non-negative; a count of zero is often valid. 🔢
• MPI_ERR_TYPE — Invalid datatype argument. Additionally, this error can occur if an uncommitted MPI_Datatype (see MPI_Type_commit) is used in a communication call. 💔
• MPI_ERR_OTHER — Other error; use MPI_Error_string to get more information about this error code. 🕵️‍♀️

also a whole extra note: the last rewritten line of the original page mentioned other stuff, so like — go read the neighbours, bestie, the SEE ALSO energy is there even if we're keeping it chill here 💜

wait, no — scratch that, no invented cross-references, that's a vibe violation 🌈. everything you need is right here on this page.

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and that's the whole page, bestie!! this was the MPI manual, version/date stamp 4/10/2026, page MPI_File_write_all(3) — collective write using individual file pointer, slay, go forth and write together 💅✨🎀