18.2.211. shmem_swap — Open MPI 5.0.8 documentation

# 18.2.211. shmem_swap

shmem_double_swap(3), shmem_float_swap(3), shmem_int_swap(3), shmem_long_swap(3), shmem_swap(3), shmem_int4_swap(3), shmem_int8_swap(3), shmem_real4_swap(3), shmem_real8_swap(3), shmem_longlong_swap(3) - Performs an atomic swap to a remote data object

## 18.2.211.1. SYNOPSIS

C or C++:

    #include <mpp/shmem.h>

    double shmem_double_swap(double *target, double value,
      int pe)

    float shmem_float_swap(float *target, float value, int pe)

    int shmem_int_swap(int *target, int value, int pe)

    long shmem_long_swap(long *target, long value, int pe)

    long long shmem_longlong_swap(long long *target,
      long long value, int pe)

    long shmem_swap(long *target, long value, int pe)

Fortran:

    INCLUDE "mpp/shmem.fh"

    INTEGER pe

    INTEGER SHMEM_SWAP
    ires = SHMEM_SWAP(target, value, pe)

    INTEGER(KIND=4) SHMEM_INT4_SWAP
    ires = SHMEM_INT4_SWAP(target, value, pe)

    INTEGER(KIND=8) SHMEM_INT8_SWAP
    ires = SHMEM_INT8_SWAP(target, value, pe)

    REAL(KIND=4) SHMEM_REAL4_SWAP
    res = SHMEM_REAL4_SWAP(target, value, pe)

    REAL(KIND=8) SHMEM_REAL8_SWAP
    res = SHMEM_REAL8_SWAP(target, value, pe)

## 18.2.211.2. DESCRIPTION

The atomic swap routines write value to address target on PE pe, and return the previous contents of target in one atomic operation.

The arguments are as follows:

target

  The remotely accessible integer data object to be updated on the remote PE. If you are using C/C++, the type of target should match that implied in the SYNOPSIS section. If you are using Fortran, it must be of the following type:

  SHMEM_SWAP: Integer of default kind

  SHMEM_INT4_SWAP: 4-byte integer

  SHMEM_INT8_SWAP: 8-byte integer

  SHMEM_REAL4_SWAP: 4-byte real

  SHMEM_REAL8_SWAP: 8-byte real

value

  Value to be atomically written to the remote PE. value is the same type as target.

pe

  An integer that indicates the PE number on which target is to be updated. If you are using Fortran, it must be a default integer value.

## 18.2.211.3. NOTES

The term remotely accessible is defined in intro_shmem(3).

## 18.2.211.4. RETURN VALUES

The contents that had been at the target address on the remote PE prior to the swap is returned.

See also

intro_shmem(3)