MPI_FILE_READ_SHARED(3)

✨ NAME ✨

okay so this is the MPI_FILE_READ_SHARED(3) page from Open MPI, and it's all about MPI_File_read_shared — the routine that reads a file using the shared file pointer (blocking, noncollective). bestie, this is the “I’m reading from the shared pointer, no collective drama” moment 💅

---

🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

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

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_FILE_READ_SHARED(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_read_shared(fh, buf, count, datatype, status, ierror)
     TYPE(MPI_File), INTENT(IN) :: fh
     TYPE(*), DIMENSION(..) :: 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 little passport for the file, basically 🫶

---

💖 INPUT PARAMETERS 💖

• count — Number of elements in buffer (integer). yes, an actual integer, not a vibe count ✨
• datatype — Data type of each buffer element (handle). this tells everyone what kind of little guys are chillin’ in the buffer 💫

---

🦋 OUTPUT PARAMETERS 🦋

• buf — Initial address of buffer (choice). the starting address, the main character location 📍
• status — Status object (status). iconic status object behavior, no cap 👑
• ierror — Fortran only: Error status (integer). Fortran’s little error report card 🍓

---

🔥 DESCRIPTION 🔥

MPI_File_read_shared is a blocking routine that uses the shared file pointer to read files. The order of serialization is not deterministic for this noncollective routine. so like, the read happens, but the exact order is giving “mystery era” 😭

---

😭 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. very “we’re ending this whole thing” energy 💀
• 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. dramatic? yes. accurate? also yes 🫶
• MPI_ERRORS_RETURN — Returns an error code to the application. the “here’s your receipt, bestie” handler 🧾

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 yeah, error time is not always “keep it moving” time 😬

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.

---

👑 COPYRIGHT 👑

2003-2026, The Open MPI Community

xoxo, from Open MPI 💖 — source/version: Open MPI, date: Sep 11, 2026. bye bestie, go read that shared file 🎀✨