MPI_START(3)

📦
version 5.0.10 · 7 versions
, in ubuntu stonking

💖 MPI_START(3) 💖

okay so bestie, welcome to the Open MPI manual page for MPI_Start and honestly? she's a baddie. let's get into it ✨

🌸 NAME 🌸

MPI_Start — initiates a communication using a persistent request handle.

it's giving "press the go button on a request that's already been prepped". main character energy fr fr 💅

✨ SYNTAX ✨

📎 C Syntax

#include <mpi.h>

int MPI_Start(MPI_Request *request)

🎀 Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_START(REQUEST, IERROR)
     INTEGER REQUEST, IERROR

🦋 Fortran 2008 Syntax

USE mpi_f08
MPI_Start(request, ierror)
     TYPE(MPI_Request), INTENT(INOUT) :: request
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🌈 INPUT PARAMETER 🌈

  • request — communication request (handle). this is your little ticket to the comm, girlie 🎟️

💜 OUTPUT PARAMETER 💜

  • ierror — Fortran only: error status (integer). yes it's an integer, no she's not optional in the old syntax, okurrr

👑 DESCRIPTION 👑

A communication (send or receive) that uses a persistent request is initiated by the function MPI_Start.

so listen. the argument request is a handle that got returned by one of the persistent communication-request initialization functions — that's MPI_Send_init, MPI_Bsend_init, MPI_Ssend_init, MPI_Rsend_init, MPI_Recv_init. your faves. the associated request should be inactive, and it becomes active once the call is made. glow up moment ✨

If the request is for a send with ready mode, then a matching receive should be posted before the call is made. 👀 yes, before. no cap. and from the time the call is made until after the operation completes, the communication buffer should not be accessed. don't touch it. it's busy. it's in her era. 🚫

The call is local, with semantics similar to the nonblocking communication operations (see Section 3.7 in the MPI Standard, “Nonblocking Communication.”). That is:

  • a call to MPI_Start with a request created by MPI_Send_init starts a communication in the same manner as a call to MPI_Isend
  • a call to MPI_Start with a request created by MPI_Bsend_init starts a communication in the same manner as a call to MPI_Ibsend
  • and so on.

it's literally the same vibe, just with a request you already made earlier instead of one you spawn on the spot. iconic behavior honestly 🫶

💀 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. (so C besties: check the return. Fortran besties: check the last arg. iykyk)

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. yes, all. she's dramatic like that 💀
  • 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. the "we can talk about this" 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.

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_Rsend_init
  • MPI_Send_init
  • MPI_Ssend_init
  • MPI_Recv_init
  • MPI_Startall

2003-2026, The Open MPI Community

and that's the whole page bestie 🥰 you now know MPI_Start better than half the internet. go forth and start those persistent requests, queen 👑 no cap, fr fr, periodt 💅✨

this page dropped Sep 10, 2026, straight from the Open MPI girlies — MPI_START(3), copyright 2003-2026, The Open MPI Community 🎀🦋

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