MPI_FILE_IREAD_ALL(3)

💫 MPI_FILE_IREAD_ALL(3) — Open MPI 💫

okay so bestie, welcome to MPI_File_iread_all 💖 this is the one from the Open MPI manual, and she is nonblocking and collective, and she reads a file starting at the location specified by the individual file pointer. main character energy fr fr ✨

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🌸 NAME 🌸

MPI_File_iread_all — Reads a file starting at the location specified by the individual file pointer (nonblocking, collective). 🦋

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✨ SYNTAX ✨

💅 C Syntax

#include <mpi.h>

int MPI_File_iread_all(MPI_File fh, void  *buf, int  count,
     MPI_Datatype  datatype, MPI_Request  *request)

💅 Fortran Syntax

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

💅 Fortran 2008 Syntax

USE mpi_f08
MPI_File_iread_all(fh, buf, count, datatype, request, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     TYPE(*), DIMENSION(..) :: buf
     INTEGER, INTENT(IN) :: count
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Request), INTENT(OUT) :: request
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

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🫶 INPUT/OUTPUT PARAMETER 🫶

• fh — File handle (handle). literally the file's whole identity bestie 🎀

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💜 INPUT PARAMETERS 💜

• count — Number of elements in the buffer (integer). that's how many she's reading, no cap ✨
• datatype — Data type of each buffer element (handle). 🧚

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🌈 OUTPUT PARAMETERS 🌈

• buf — Initial address of buffer (choice). the cozy little landing spot for your data 🍓
• request — Request object (handle). your ticket to come back and check on her later 💅
• ierror — Fortran only: Error status (integer). 🙈

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👑 DESCRIPTION 👑

okay so MPI_File_iread_all is the nonblocking version of MPI_File_read_all. she attempts to read from the file associated with fh — at the current individual file pointer position maintained by the system — and in which a total number of count data items having datatype type are read into the user's buffer buf. 📖✨

the data is taken out of those parts of the file specified by the current view. so like, the view is the vibe check for where the data lives, iykyk 🌸

MPI_File_iread_all stores the number of data-type elements actually read in status. all other fields of status are undefined. ⭐

🚨 real talk bestie: it is erroneous to call this function if MPI_MODE_SEQUENTIAL mode was specified when the file was opened. don't do it. fr fr 💀

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💀 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. she might just not recover bestie 🫶

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!! 🌟 written by the Open MPI girlies, Sep 11, 2026, for MPI_FILE_IREAD_ALL(3) — now go read that file collectively and nonblockingly, periodt 💅✨🦋