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MPI_Compare_and_swap

:ref:`MPI_Compare_and_swap` - Perform RMA compare-and-swap

SYNTAX

C Syntax

#include <mpi.h>

int MPI_Compare_and_swap(const void *origin_addr, const void *compare_addr,
     void *result_addr, MPI_Datatype datatype, int target_rank,
     MPI_Aint target_disp, MPI_Win win)

Fortran Syntax

USE MPI
! or the older form: INCLUDE 'mpif.h'
MPI_COMPARE_AND_SWAP(ORIGIN_ADDR, COMPARE_ADDR, RESULT_ADDR, DATATYPE, TARGET_RANK,
     TARGET_DISP, WIN, IERROR)
     <type> ORIGIN_ADDR, COMPARE_ADDR, RESULT_ADDR(*)
     INTEGER(KIND=MPI_ADDRESS_KIND) TARGET_DISP
     INTEGER DATATYPE, TARGET_RANK, WIN, IERROR

Fortran 2008 Syntax

USE mpi_f08
MPI_Compare_and_swap(origin_addr, compare_addr, result_addr, datatype,
             target_rank, target_disp, win, ierror)
     TYPE(*), DIMENSION(..), INTENT(IN) :: origin_addr, compare_addr
     TYPE(*), DIMENSION(..) :: result_addr
     TYPE(MPI_Datatype), INTENT(IN) :: datatype
     INTEGER, INTENT(IN) :: target_rank
     INTEGER(KIND=MPI_ADDRESS_KIND), INTENT(IN) :: target_disp
     TYPE(MPI_Win), INTENT(IN) :: win
     INTEGER, OPTIONAL, INTENT(OUT) :: ierror

INPUT PARAMETERS

  • origin_addr: Initial address of buffer (choice).
  • compare_addr: Initial address of compare buffer (choice).
  • result_addr: Initial address of result buffer (choice).
  • datatype: Data type of the entry in origin, result, and target buffers (handle).
  • target_rank: Rank of target (nonnegative integer).
  • target_disp: Displacement from start of window to beginning of target buffer (nonnegative integer).
  • win: Window object (handle).

OUTPUT PARAMETER

  • ierror: Fortran only: Error status (integer).

DESCRIPTION

This function compares one element of type datatype in the compare buffer compare_addr with the buffer at offset target_disp in the target window specified by target_rank and win and replaces the value at the target with the value in the origin buffer origin_addr if the compare buffer and the target buffer are identical. The original value at the target is returned in the buffer result_addr. The parameter datatype must belong to one of the following categories of predefined datatypes: C integer, Fortran integer, Logical, Multi-language types, or Byte as specified in MPI-3 section 5.9.2 on page 176.

The origin and result buffers (origin_addr and result_addr) must be disjoint.

NOTES

It is the user's responsibility to guarantee that, when using the accumulate functions, the target displacement argument is such that accesses to the window are properly aligned according to the data type arguments in the call to the :ref:`MPI_Compare_and_swap` function.

ERRORS