MPI_SSEND_INIT(3)

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💌 MPI_Ssend_init — the Open MPI glow-up (section 3 of the manual, bestie)

Okay so this is the MPI_SSEND_INIT(3) page from Open MPI, and it's literally all about building a handle for a synchronous send. Like, a pre-packaged send. You set it up once, you fire it off whenever. Obsessed. 🎀

✨ SYNTAX ✨

🌸 C Syntax

#include <mpi.h>

int MPI_Ssend_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_SSEND_INIT(BUF, COUNT, DATATYPE, DEST, TAG, COMM, REQUEST,
             IERROR)
     <type>  BUF(*)
     INTEGER COUNT, DATATYPE, DEST, TAG, COMM, REQUEST, IERROR

🌸 Fortran 2008 Syntax

USE mpi_f08
MPI_Ssend_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 🫶

These are the lil things you gotta hand over so the function knows what's up:

  • buf — the initial address of your send buffer (a choice, iykyk). This is where the data lives, bestie. 📦
  • count — how many elements you're sending (integer). Count them. Fr fr.
  • datatype — the type of each element (handle). Gotta know what you're working with. 💅
  • dest — rank of the destination (integer). Who's receiving this masterpiece? 👑
  • tag — the message tag (integer). Label your mail. ✉️
  • comm — the communicator (handle). The friend group, basically. 🌈

💖 OUTPUT PARAMETERS 💖

  • request — the communication request (handle). This is your shiny new toy — hold onto it! 🎀
  • ierror — Fortran only: error status (integer). Only the Fortran girlies get this one. 🍓

🦋 DESCRIPTION 🦋

So what does it do? It creates a persistent communication object for a synchronous mode send operation — and it binds to it, like, all the arguments of a send operation. Every single one. No cap. ✨

The way this works: a communication (send or receive) that uses a persistent request gets initiated by the function MPI_Start. So you build the thing here, and then MPI_Start is the little "go go go" button. Iconic separation of concerns, honestly. 🔥

💀 ERRORS 💀

Okay bestie, listen up, because this part is long but it matters.

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. Everyone out. 💀
  • 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. Very "it depends on the context" of it. 🙈
  • MPI_ERRORS_RETURN — Returns an error code to the application. The chill one. Hands you the receipt and lets you deal. 🧾

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, that's not a vibe it's a warning. Take it seriously, 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. 🎓

👀 SEE ALSO — go read these next 👀

  • MPI_Bsend_init
  • MPI_Send_init
  • MPI_Rsend_init
  • MPI_Recv_init
  • MPI_Start
  • MPI_Startall
  • MPI_Ssend

2003-2026, The Open MPI Community — protecting the girlies since 2003. 💜

✨ and that's the whole page, bestie ✨ — brought to you by Open MPI, dated Sep 11, 2026, filed lovingly under MPI_SSEND_INIT(3). Go forth and send synchronously. You've got this. 🦋💅🎀

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