MPI_FILE_WRITE_AT_ALL(3)

📦
version 5.0.11 · 17 versions
, in arch rolling

💖 NAME 💖

MPI_FILE_WRITE_AT_ALL(3) from Open MPI — MPI_File_write_at_all — Writes a file at explicitly specified offsets (blocking, collective). periodt 💅

🛠️ SYNTAX 🛠️

C Syntax

          #include <mpi.h>

          int MPI_File_write_at_all(MPI_File fh, MPI_Offset offset, 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_AT_ALL(FH, OFFSET, BUF, COUNT,
               DATATYPE, STATUS, IERROR)
               <type>  BUF(*)
               INTEGER FH, COUNT, DATATYPE, STATUS(MPI_STATUS_SIZE), IERROR
               INTEGER(KIND=MPI_OFFSET_KIND)   OFFSET

Fortran 2008 Syntax

          USE mpi_f08
          MPI_File_write_at_all(fh, offset, buf, count, datatype, status, ierror)
               TYPE(MPI_File), INTENT(IN) :: fh
               INTEGER(KIND=MPI_OFFSET_KIND), INTENT(IN) :: offset
               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 PARAMETERS 📥

  • fh — File handle (handle). the file bestie in question 🫶
  • offset — File offset (integer). where the writing starts, in etype units relative to the current view ✨
  • buf — Initial address of buffer (choice). your precious data goes here 🍓
  • count — Number of elements in buffer (integer). how many of them we’re talking about 🔢
  • datatype — Data type of each buffer element (handle). the flavor of each element 🦋

📤 OUTPUT PARAMETERS 📤

  • status — Status object (status). stores how many datatype elements actually got written; every other field is undefined, no cap 😭
  • ierror — Fortran only: Error status (integer). the Fortran-only error vibe check 💀

✨ DESCRIPTION ✨

Okay so MPI_File_write_at_all is a collective routine that attempts to write into the file associated with fh — at the offset position — a total number of count data items having datatype type from the user’s buffer buf. collective means the whole squad is in on it 👑

The offset is in etype units relative to the current view. That is, holes are not counted when locating an offset. iykyk 🕳️✨

The data is written into those parts of the file specified by the current view. MPI_File_write_at_all stores the number of datatype elements actually written in status. All other fields of status are undefined. so don’t go reading random extra stuff out of it, bestie 🙈

⚠️ It is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened. like, do not do that. it’s giving undefined behavior energy 💀

💀 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. classic MPI behavior, bestie 🫶

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. so it’s lowkey always got somewhere to send the error ✨

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. very “choose your own adventure” of you 🎀

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. so yes, errors really said “we ride at dawn” for non-I/O 🔥

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

  • MPI_ERRORS_ARE_FATAL — Causes the program to abort all connected MPI processes. dramatic? yes. accurate? also yes 💀
  • 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. abort with range, honestly 👑
  • MPI_ERRORS_RETURN — Returns an error code to the application. the “give it back to me, I’ll deal” option 🫶

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. like, after an error it might simply not be that girl anymore 😭

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. the lore is there if you want it 📚✨

2003-2026, The Open MPI Community. protect the community, bestie 💖

signed, sealed, and sent with love from source/version: <strong>Open MPI</strong> · page date: <strong>Sep 11, 2026</strong> 🎀💅🫶

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