MPI_PRECV_INIT(3)

💅 MPI_Precv_init — the manual page, but make it make sense ✨

okay so bestie, you found MPI_Precv_init in the Open MPI manual (that's the MPI_PRECV_INIT(3) page, mwah) and honestly? It's giving "niche but iconic". It initializes a partitioned receive. That's it, that's the vibe. Let's get into it 💖

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🌸 SYNTAX 🌸

C Syntax

#include <mpi.h>

int MPI_Precv_init(const void *buf, int partitions, int count, MPI_Datatype datatype,
     int source, int tag, MPI_Comm comm, MPI_Info info, MPI_Request *request)

Fortran Syntax

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

Fortran 2008 Syntax

USE mpi_f08
MPI_Precv_init(buf, partitions, count, datatype, source, tag, comm, info, request, ierror)
     TYPE(*), DIMENSION(..), INTENT(IN), ASYNCHRONOUS :: buf
     INTEGER, INTENT(IN) :: partitions, count, source, tag
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     TYPE(MPI_Comm), INTENT(IN) :: comm
     TYPE(MPI_Info), INTENT(IN) :: info
     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 — the initial address of the receive buffer (it's a choice, so pick your type, bestie).
• partitions — the number of partitions (integer).
• count — how many elements get received per partition (integer).
• datatype — the datatype of each element (handle).
• source — the rank of the source (integer).
• tag — the message tag (integer).
• comm — the communicator (handle).
• info — the info argument (handle).

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🦋 OUTPUT PARAMETERS 🦋

what you get back, and yes it's cute:

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

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🚨 ERRORS 🚨

okay so this part is long but it's important, don't skip it 💀

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.
• 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.

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.

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👑 NOTE 👑

🚧 real talk, bestie: the current implementation is an early prototype and is not fully compliant with the MPI-4.0 specification. Specifically this function and it's counterpart (MPI_Psend_init) will block until the partitioned communication request is initialized on both ends. This behavior will be corrected in future versions. So like… it works, but it's in its experimental era 😭

See also:

• MPI_Psend_init

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📜 Copyright

2003-2026, The Open MPI Community

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and that's the whole page, you ate it 💅🫶 this was MPI_PRECV_INIT(3) from the Open MPI crew — page dated Sep 10, 2026 — go forth and partition your receives, no cap ✨🌈