MPI_RECV_INIT(3)

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version 5.0.10 · 7 versions
, in ubuntu stonking

💖 MPI_RECV_INIT(3) — Open MPI, bestie edition 💖

okay so. MPI_Recv_init — Builds a handle for a receive. and when i say handle i mean it, this is the girl that gets you ready to receive, she does not actually receive. she's the pregame. the getting-ready-with-me. the outfit planning. the actual party is MPI_Start and you KNOW it. 🎀

this page lives in the Open MPI manual, third edition, and it's literally the blueprint for persistent receives so let's get into it ✨

🌈 SYNTAX 🌈

✨ C Syntax

#include <mpi.h>

int MPI_Recv_init(void *buf, int count, MPI_Datatype datatype,
     int source, int tag, MPI_Comm comm, MPI_Request *request)

✨ Fortran Syntax

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

✨ Fortran 2008 Syntax

USE mpi_f08
MPI_Recv_init(buf, count, datatype, source, tag, comm, request, ierror)
     TYPE(*), DIMENSION(..), ASYNCHRONOUS :: buf
     INTEGER, INTENT(IN) :: count, source, 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 📥

  • count: Maximum number of elements to receive (integer). the max, bestie, not the vibe, the literal ceiling 🧚
  • datatype: Type of each entry (handle). what kind of girl each element is 💅
  • source: Rank of source (integer). who's sliding into your mailbox 👀
  • tag: Message tag (integer). the little label so you know which message is which 🏷️
  • comm: Communicator (handle). the group chat everyones operating in 🫶

🔄 INPUT/OUTPUT PARAMETER 🔄

  • buf: Initial address of receive buffer (choice). yes it's both, it's giving duality, it's giving main character, keep reading for why 😭

📤 OUTPUT PARAMETERS 📤

  • request: Communication request (handle). your little ticket, hold onto it 🔥
  • ierror: Fortran only: Error status (integer). fortran girlies get the extra receipt ✨

💫 DESCRIPTION 💫

Creates a persistent communication request for a receive operation. think of it as pre-ordering your coffee so future-you doesn't have to explain the whole order again. the request just exists, chilling, waiting for its moment.

The argument buf is marked as OUT because the user gives permission to write on the receive buffer by passing the argument to MPI_Recv_init. so basically you're handing over the keys to your buffer by even mentioning it here. consent first, always. 🫶

A persistent communication request is inactive after it is created — no active communication is attached to the request. she's dressed, she's ready, she has not left the house. periodt. 💅

A communication (send or receive) that uses a persistent request is initiated by the function MPI_Start or MPI_Startall. THOSE are the ones who actually make the thing happen. ✨

💀 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. she does NOT play, everything stops 🛑
  • 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. okay so context matters, it's giving "know your audience" 😭
  • MPI_ERRORS_RETURN Returns an error code to the application. she just hands you the note and walks away 💌

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. no cap, this one's real. 😭

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_Start
  • MPI_Startall
  • MPI_Request_free

2003-2026, The Open MPI Community

and that's the whole page, bestie 💖 written by the Open MPI girlies, dated Sep 10, 2026, and it lives in the MPI_RECV_INIT(3) section of the Open MPI third-edition manual. go forth and receive (after you MPI_Start, ofc) 🦋✨

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