18.2.304. MPI_Rget — Open MPI 5.0.2 documentation

# 18.2.304. MPI_Rget

MPI_Get, MPI_Rget - Copies data from the target memory to the origin.

## 18.2.304.1. SYNTAX

### 18.2.304.1.1. 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)

### 18.2.304.1.2. 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

### 18.2.304.1.3. 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

## 18.2.304.2. INPUT PARAMETERS

- `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)

## 18.2.304.3. OUTPUT PARAMETER

- `request` : MPI_Rget: RMA request

- `ierror` : Fortran only: Error status (integer).

## 18.2.304.4. DESCRIPTION

MPI_Get copies data from the target memory to the origin, similar to MPI_Put, except that the direction of data transfer is reversed. The origin_datatype may not specify overlapping entries in the origin buffer. The target buffer must be contained within the target window, and the copied data must fit, without truncation, in the origin buffer. Only processes within the same node can access the target window.

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. If origin_addr points to memory attached to a window, then the data becomes available in the private copy of this window.

## 18.2.304.5. 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.

- `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.

See also

MPI_Put