MPI_FILE_WRITE(3)

📦
version 5.0.10 · 7 versions
, in ubuntu stonking

💅 MPI_FILE_WRITE(3) — the Open MPI glow-up

ok so bestie. welcome to the MPI_FILE_WRITE(3) page, from the Open MPI manual, and we are about to make writing files at your own personal file-pointer position sound as fun as it actually is. this is MPI_File_write — Writes a file starting at the location specified by the individual file pointer (blocking, noncollective). 👑

✨ NAME ✨

MPI_File_write — Writes a file starting at the location specified by the individual file pointer (blocking, noncollective).

like. it writes. into a file. at your individual file pointer. and it blocks. and it is not collective, so it's not a group project, it's a solo era. 🎀

🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

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

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_WRITE(FH, BUF, COUNT,
     DATATYPE, STATUS, IERROR)
     <type>  BUF(*)
     INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_File_write(fh, buf, count, datatype, status, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     TYPE(*), DIMENSION(..), INTENT(IN) :: buf
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🦋 INPUT/OUTPUT PARAMETER 🦋

  • fh — File handle (handle). it's the lil badge that says which file we're talking to. 💖

🌈 INPUT PARAMETERS 🌈

  • buf — Initial address of buffer (choice). where your actual data is chillin', waiting to be yeeted into the file. ✨
  • count — Number of elements in buffer (integer). how many datatype lil guys you're sending. 🍓
  • datatype — Data type of each buffer element (handle). what kind of element each of those count things is. 💅

💜 OUTPUT PARAMETERS 💜

  • status — Status object (status). it holds the receipts.
  • ierror — Fortran only: Error status (integer). Fortran besties get their error handed to them in the last arg. 🫶

🎀 DESCRIPTION 🎀

ok so the way that MPI_File_write works is: it attempts to write into the file associated with fh — at the current individual file pointer position maintained by the system — a total number of count data items having datatype type, from the user's buffer buf. 🦋

and the data doesn't just go anywhere, bestie. it gets written into those parts of the file specified by the current view. very demure, very mindful, very view-aware. 🌸

then MPI_File_write stores the number of datatype elements actually written in status. all other fields of status are undefined. so like… don't go reading the other fields, they're giving mystery on purpose. 💀

⚠️ it is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened. like genuinely, don't. that's not a vibe, that's a bug. 🙈

🔥 ERRORS 🔥

Almost all MPI routines return an error value — C routines as the return result of the function, and Fortran routines in the last argument. ☝️

Before the error value is returned, the current MPI error handler associated with the communication object (e.g., communicator, window, file) is called. If no communication object is associated with the MPI call, then the call is considered attached to MPI_COMM_SELF and will call the associated MPI error handler. When MPI_COMM_SELF is not initialized (i.e., before MPI_Init/MPI_Init_thread, after MPI_Finalize, or when using the Sessions Model exclusively) the error raises the initial error handler. The initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or the mpi_initial_errhandler CLI argument to mpiexec or info key to MPI_Comm_spawn/MPI_Comm_spawn_multiple. If no other appropriate error handler has been set, then the MPI_ERRORS_RETURN error handler is called for MPI I/O functions and the MPI_ERRORS_ABORT error handler is called for all other MPI functions. 😭

Open MPI includes three predefined error handlers that can be used:

  • MPI_ERRORS_ARE_FATAL — Causes the program to abort all connected MPI processes. 💀
  • MPI_ERRORS_ABORT — An error handler that can be invoked on a communicator, window, file, or session. When called on a communicator, it acts as if MPI_Abort was called on that communicator. If called on a window or file, acts as if MPI_Abort was called on a communicator containing the group of processes in the corresponding window or file. If called on a session, aborts only the local process.
  • MPI_ERRORS_RETURN — Returns an error code to the application.

MPI applications can also implement their own error handlers by calling:

  • MPI_Comm_create_errhandler then MPI_Comm_set_errhandler
  • MPI_File_create_errhandler then MPI_File_set_errhandler
  • MPI_Session_create_errhandler then MPI_Session_set_errhandler or at MPI_Session_init
  • MPI_Win_create_errhandler then MPI_Win_set_errhandler

Note that MPI does not guarantee that an MPI program can continue past an error.

See the MPI man page for a full list of MPI error codes.

See the Error Handling section of the MPI-3.1 standard for more information. 📚

2003-2026, The Open MPI Community 🫶

ok that's the whole page, no notes, and it slayed. this tea was served to you by the Open MPI crew, source/version vibes from Sep 10, 2026, and yes the page really is called MPI_FILE_WRITE(3) — periodt. 💖✨🌸🦋💅

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