MPI_BSEND_INIT(3)

🎀 MPI_BSEND_INIT 💅

okay bestie, this one comes straight out of the Open MPI manual, section 3 — that's the library-calls section, iykyk. it's a persistent buffered send situation and honestly? it's giving main character energy for your communication patterns ✨

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🌸 NAME 🌸

MPI_Bsend_init — builds a handle for a buffered send. that's it, that's the whole job. a little handle. a lil key 🔑 to a buffered send you get to reuse. iconic.

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✨ SYNTAX ✨

🌈 C Syntax

#include <mpi.h>

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

🧚 Fortran 2008 Syntax

USE mpi_f08

MPI_Bsend_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

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💖 INPUT PARAMETERS 💖

these are the things you hand over, no take-backsies:

• buf — initial address of send buffer (choice). where the good stuff lives 🫶
• count — number of elements sent (integer). count 'em.
• datatype — type of each element (handle).
• dest — rank of destination (integer). who's getting the message 👑
• tag — message tag (integer).
• comm — communicator (handle). the group chat, basically.

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🌟 OUTPUT PARAMETERS 🌟

what you get back, and it's a lot, actually:

• request — communication request (handle).
• ierror — Fortran only: error status (integer).

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💫 DESCRIPTION 💫

so what does it actually do? it creates a persistent communication request for a buffered mode send, and it binds to that request all the arguments of a send operation. every single one. locked in, fr fr 🔒

a communication (send or receive) that uses a persistent request is initiated by the function MPI_Start <#mpi-start>. that's how you actually fire it off — the init just sets the whole thing up 💅

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😭 ERRORS 😭

okay so this part is long but hear me out, 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> / MPI_Init_thread <#mpi-init-thread>, after MPI_Finalize <#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 <#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> / MPI_Comm_spawn_multiple <#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. yeah. everybody. 💀
• 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 <#mpi-abort> was called on that communicator. if called on a window or file, acts as if MPI_Abort <#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 polite one 🫶

MPI applications can also implement their own error handlers by calling:

• MPI_Comm_create_errhandler <#mpi-comm-create-errhandler> then MPI_Comm_set_errhandler <#mpi-comm-set-errhandler>
• MPI_File_create_errhandler <#mpi-file-create-errhandler> then MPI_File_set_errhandler <#mpi-file-set-errhandler>
• MPI_Session_create_errhandler <#mpi-session-create-errhandler> then MPI_Session_set_errhandler <#mpi-session-set-errhandler> or at MPI_Session_init <#mpi-session-init>
• MPI_Win_create_errhandler <#mpi-win-create-errhandler> then MPI_Win_set_errhandler <#mpi-win-set-errhandler>

note that MPI does not guarantee that an MPI program can continue past an error. like, do not count on it bestie, that's a real caveat 🚨

see the MPI man page <#open-mpi> for a full list of MPI error codes <#open-mpi-errors>.

see the Error Handling section of the MPI-3.1 standard for more information.

See also: MPI_Send_init <#mpi-send-init> MPI_Start <#mpi-start>

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🍓 SEE ALSO 🍓

• MPI_Send_init <#mpi-send-init> — same energy, but non-buffered 🌈
• MPI_Start <#mpi-start> — the one that actually kicks it off 🔥

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👑 Copyright 👑

2003-2026, The Open MPI Community

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so yeah, that's the whole page, and that's a wrap on Open MPI, dated Sep 10, 2026 — go forth and MPI_Start responsibly, bestie, you've got this 💜🦋✨