MPI_FILE_READ_AT_ALL_END(3)

💅 MPI_FILE_READ_AT_ALL_END(3) — an Open MPI moment ✨

okay so bestie, welcome to the ending half of a split collective routine, from the Open MPI manual, page MPI_FILE_READ_AT_ALL_END(3). This one reads a file at explicitly specified offsets — and it's the closing act. The finale. The "and scene" 🎬

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🌸 NAME 🌸

MPI_File_read_at_all_end — reads a file at explicitly specified offsets; this is the ending part of a split collective routine, and bestie it is blocking. periodt.

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✨ SYNTAX ✨

🎀 C Syntax

#include <mpi.h>

int MPI_File_read_at_all_end(MPI_File fh, void *buf,
     MPI_Status *status)

🦋 Fortran Syntax

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

🧚 Fortran 2008 Syntax

USE mpi_f08
MPI_File_read_at_all_end(fh, buf, status, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
     TYPE(MPI_Status) :: status
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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💖 INPUT PARAMETER 💖

• fh — the file handle, iykyk. (handle)

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🌈 OUTPUT PARAMETERS 🌈

• buf — initial address of the buffer, bestie. (choice)
• status — the status object, living its main character life. (status)
• ierror — Fortran only: the error status, an integer. (integer)

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👑 DESCRIPTION 👑

So MPI_File_read_at_all_end is a split collective routine, and what it does is store the number of elements actually read from the file associated with fh in status. Not me being dramatic — that's literally the whole job 💅

It blocks until the operation that MPI_File_read_at_all_begin kicked off is complete. Iconic teamwork. The data gets taken out of those parts of the file specified by the current view. And every other field of status? Undefined. Don't look at them. They're not for you. 🙈

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🍓 NOTES 🍓

All the nonblocking collective routines for data access are "split" into two routines, each with a _begin or _end suffix — so yes, this is one half of a beautiful little duo 🫶 These split collective routines are subject to the semantic rules described in Section 9.4.5 of the MPI-2 standard. Go read it, bestie, it's giving homework but make it MPI.

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💀 ERRORS 💀

Almost all MPI routines return an error value, fr fr: 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) gets 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. That 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 the 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 you can use, and honestly? slay:

• 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, it 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, it 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. Like, at all. Just so you know.

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.

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🎬 COPYRIGHT 🎬

2003-2026, The Open MPI Community 💜

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and that's the whole page, bestie! ✨ This one's brought to you by the Open MPI girlies, dated Sep 11, 2026 — MPI_FILE_READ_AT_ALL_END(3), out. 🦋💅