MPI_GET(3)

📦
version 5.0.11 · 17 versions
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💖 NAME 💖

MPI_Get, MPI_Rget — copies data from the target memory to the origin. yes bestie, it's a pull, not a push. we're getting, not putting. iconic behavior honestly.

(also hi, this is from the Open MPI manual, page MPI_GET(3) — putting that here so you're not lost 🫶)

✨ SYNTAX ✨

C Syntax

#include <mpi.h>

MPI_Get(void *origin_addr, int origin_count, MPI_Datatype
    origin_datatype, int target_rank, MPI_Aint target_disp,
    int target_count, MPI_Datatype target_datatype, MPI_Win win)

MPI_Rget(void *origin_addr, int origin_count, MPI_Datatype
     origin_datatype, int target_rank, MPI_Aint target_disp,
     int target_count, MPI_Datatype target_datatype, MPI_Win win,
         MPI_Request *request)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'

MPI_GET(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
    TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, WIN, IERROR)
    <type> ORIGIN_ADDR(*)
    INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
    INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
    TARGET_COUNT, TARGET_DATATYPE, WIN, IERROR

MPI_RGET(ORIGIN_ADDR, ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
     TARGET_DISP, TARGET_COUNT, TARGET_DATATYPE, WIN, REQUEST, IERROR)
     <type> ORIGIN_ADDR(*)
     INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
     INTEGER ORIGIN_COUNT, ORIGIN_DATATYPE, TARGET_RANK,
     TARGET_COUNT, TARGET_DATATYPE, WIN, REQUEST, IERROR

Fortran 2008 Syntax

USE mpi_f08

MPI_Get(origin_addr, origin_count, origin_datatype, target_rank,
        target_disp, target_count, target_datatype, win, ierror)
    TYPE(*), DIMENSION(..), ASYNCHRONOUS :: origin_addr
    INTEGER, INTENT(IN) :: origin_count, target_rank, target_count
    TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
    INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
    TYPE(MPI_Win), INTENT(IN) :: win
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

MPI_Rget(origin_addr, origin_count, origin_datatype, target_rank,
    target_disp, target_count, target_datatype, win, request,
        ierror)
    TYPE(*), DIMENSION(..), ASYNCHRONOUS :: origin_addr
    INTEGER, INTENT(IN) :: origin_count, target_rank, target_count
    TYPE(MPI_Datatype), INTENT(IN) :: origin_datatype, target_datatype
    INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
    TYPE(MPI_Win), INTENT(IN) :: win
    TYPE(MPI_Request), INTENT(OUT) :: request
    INTEGER, OPTIONAL, INTENT(OUT) :: ierror

🌸 INPUT PARAMETERS 🌸

okay so here's everyone in the group chat:

  • origin_addr — Initial address of origin buffer (choice).
  • origin_count — Number of entries in origin buffer (nonnegative integer).
  • origin_datatype — Data type of each entry in origin buffer (handle).
  • target_rank — Rank of target (nonnegative integer).
  • target_disp — Displacement from window start to the beginning of the target buffer (nonnegative integer).
  • target_count — Number of entries in target buffer (nonnegative integer).
  • target datatype — datatype of each entry in target buffer (handle)
  • win — window object used for communication (handle)

(yes the original spells it target datatype with a space — i'm not gonna gaslight you and pretend otherwise 💅)

🦋 OUTPUT PARAMETER 🦋

  • request — MPI_Rget: RMA request
  • ierror — Fortran only: Error status (integer).

💜 DESCRIPTION 💜

So MPI_Get copies data from the target memory to the origin — it's literally MPI_Put but the direction of data transfer is reversed. same energy, opposite lane. we are RECEIVING, not sending. 🔥

Some ground rules though, no cap:

  • The origin_datatype may not specify overlapping entries in the origin buffer. (like, don't do that. fr.)
  • The target buffer must be contained within the target window.
  • The copied data must fit, without truncation, in the origin buffer.
  • Only processes within the same node can access the target window. 🫶

Now MPI_Rget is similar to MPI_Get, except that it allocates a communication request object and associates it with the request handle (the argument request) that can be used to wait or test for completion. the completion of an MPI_Rget operation indicates that the data is available in the origin buffer. and if origin_addr points to memory attached to a window, then the data becomes available in the private copy of this window. ✨

😭 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. (classic.)

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. like, it might just be over. 🙈

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_Put — the other half of this duo, go read it bestie 💖

2003-2026, The Open MPI Community

alright that's the whole thing, you ate it up honestly 🌈 and just so we're cute and complete: this page is from Open MPI, the MPI_GET(3) page, dated Sep 11, 2026 — so like, copyright 2003-2026, The Open MPI Community, mwah 💋 go forth and MPI_Get responsibly bestie 🦋✨

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