MPI_FILE_GET_SIZE(3)

💖 MPI_FILE_GET_SIZE(3) — an Open MPI moment 💖

okay bestie, sit down, hydrate, because today we're learning how to ask a file how big are you and getting an actual answer. this is MPI_File_get_size from the Open MPI fam, and yes, it's exactly as iconic as it sounds. 🎀

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✨ NAME ✨

MPI_File_get_size — Returns the current size of the file. 💅

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🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

int MPI_File_get_size(MPI_File fh, MPI_Offset *size)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_GET_SIZE(FH, SIZE, IERROR)
     INTEGER FH, ERROR
     INTEGER(KIND=MPI_OFFSET_KIND)   SIZE

Fortran 2008 Syntax

USE mpi_f08
MPI_File_get_size(fh, size, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     INTEGER(KIND=MPI_OFFSET_KIND), INTENT(OUT) :: size
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🦋 INPUT PARAMETERS 🦋

• fh — the File handle (handle). it's the lil passport for your file, no cap. 🛂
• size — Size of the file in bytes (integer). yes bestie this one's listed here, we're just reporting the lore exactly as it is. 🙈

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👑 OUTPUT PARAMETER 👑

• ierror — Fortran only: Error status (integer). 🫶

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💜 DESCRIPTION 💜

MPI_File_get_size returns, in size, the current size in bytes of the file associated with the file handle fh. that's it, that's the whole job, and it ate. ✨

but listen — note that the file size returned by Solaris may not represent the number of bytes physically allocated for the file in those cases where all bytes in this file have not been written at least once. so if you're on Solaris and you never wrote to certain bytes, the vibes are... ambiguous. highkey important, don't skip it. 💀

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😭 ERRORS 😭

Almost all MPI routines return an error value — C routines hand it back as the return result of the function, and Fortran routines put it in the last argument. fr fr.

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. dramatic much? yes. on purpose. 💀
• 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. the chill one. 🧚

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. 🔥 (so like, don't treat errors as a cute lil suggestion.)

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.

See also: - MPI_File_preallocate

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🌈 Copyright 🌈

2003-2026, The Open MPI Community 🫶

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aaaand that's the whole page, bestie!! dated Sep 10, 2026, straight from the Open MPI girlies themselves, and the page you just read is literally titled MPI_FILE_GET_SIZE(3) — go forth and size your files, periodt 💅✨🌸