MPI_SEND_INIT(3)

📦
version 5.0.11 · 17 versions
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💌 MPI_SEND_INIT(3) — like, the Open MPI one, bestie

okay so picture this: you're in the Open MPI cinematic universe (manual page MPI_SEND_INIT, section 3, iykyk) and you need to build a handle for a standard send. That's literally the whole ~vibe~ of this page. Let's get into it 🫶

✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Send_init(const void *buf, int count, MPI_Datatype datatype,
     int dest, int tag, MPI_Comm comm, MPI_Request *request)

🎀 Fortran Syntax

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

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Send_init(buf, count, datatype, dest, tag, comm, request, ierror)
     TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
     INTEGER, INTENT(IN) :: count, dest, tag
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Comm), INTENT(IN) :: comm
     TYPE(MPI_Request), INTENT(OUT) :: request
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

💅 INPUT PARAMETERS

  • buf — the initial address of the send buffer (it's a choice, so it can be whatever type fits your little heart's desire).
  • count — how many elements you're sending (an integer, no decimals bestie).
  • datatype — the type of each element (a handle ✨).
  • dest — rank of the destination (integer). Where it's going!!
  • tag — the message tag (integer). Your little labeled baggie 🎀
  • comm — the communicator (a handle).

🌟 OUTPUT PARAMETERS

  • request — the communication request (a handle). This is the whole point, she's the main character 👑
  • ierror — Fortran only: error status (integer).

💖 DESCRIPTION 💖

So what she does: creates a persistent communication request for a standard mode send operation, and binds to it all the arguments of a send operation. iconic behavior.

And a communication (send or receive, either one) that uses a persistent request gets initiated by the function MPI_Start or MPI_Startall. That's the vibe check — nothing happens till you start it 🚦

😭 ERRORS 😭

Okay, buckle up, because 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 that error value gets returned, the current MPI error handler associated with the communication object (like, a communicator, window, or file) is called. And 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. And that initial error handler can be changed by calling MPI_Comm_set_errhandler on MPI_COMM_SELF when using the World model, or by the mpi_initial_errhandler CLI argument to mpiexec, or by 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 you can use, periodt:

  • MPI_ERRORS_ARE_FATAL — causes the program to abort all connected MPI processes. yeah. all of them. 🫠
  • 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. 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. like, no promises bestie, that's just how it is 😭

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_Bsend_init
  • MPI_Ssend_init
  • MPI_Rsend_init
  • MPI_Recv_init
  • MPI_Start
  • MPI_Startall
  • MPI_Request_free

2003-2026, The Open MPI Community

and that's a wrap on our little journey through MPI_SEND_INIT(3) 💜 — this whole moment was brought to you by the Sep 11, 2026 edition of the Open MPI man pages, written by the absolute icons over at The Open MPI Community (2003-2026). slay, go start some persistent requests 🎀✨

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