SYNOPSIS

       C or C++:

          #include <mpp/shmem.h>

          int shmem_int_cswap(int *target, int cond, int value, int pe)

          long shmem_long_cswap(long *target, long cond, long value,
            int pe)

          long long shmem_longlong_cswap(longlong *target,
            longlong cond, longlong value, int pe)

       Fortran:

          INCLUDE "mpp/shmem.fh"

          INTEGER pe

          INTEGER(KIND=4) SHMEM_INT4_CSWAP
          ires = SHMEM_INT4_CSWAP(target, cond, value, pe)

          INTEGER(KIND=8) SHMEM_INT8_CSWAP
          ires = SHMEM_INT8_CSWAP(target, cond, value, pe)

DESCRIPTION

       The conditional swap routines conditionally update a  target  data  object  on  an  arbitrary  processing
       element (PE) and return the prior contents of the data object 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  the
              Fortran  compiler,  it  must be of type integer with an element size of 4 bytes for SHMEM_INT4_ADD
              and 8 bytes for SHMEM_INT8_ADD.

       value  The value to be atomically added to target. If you are using C/C++, the type of value should match
              that implied in the SYNOPSIS section.  If you are using Fortran, it must be of type  integer  with
              an element size of target.

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

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

              SHMEM_INT4_CSWAP: 4-byte integer

              SHMEM_INT8_CSWAP: 8-byte integer

       cond   cond  is  compared to the remote target value. If cond and the remote target are equal, then value
              is swapped into the remote target.  Otherwise, the remote target is unchanged. In either case, the
              old value of the remote target is returned as the function return value.  cond must be of the same
              data type as target.

       value  The value to be atomically written to the remote PE. value must be the same data type as target.

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

NOTES

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

RETURN VALUES

       The contents that had been in the target data object on the remote PE prior to the conditional swap.

EXAMPLES

       The  following call ensures that the first PE to execute the conditional swap will successfully write its
       PE number to race_winner on PE 0.

          main()
          {
            static int race_winner = -1;
            int oldval;

            shmem_init();
            oldval = shmem_int_cswap(&race_winner, -1, shmem_my_pe(), 0);
            if (oldval == -1)
              printf("pe %d was first\n",shmem_my_pe());
          }

       SEE ALSO:
          intro_shmem(3) shmem_cache(3) shmem_swap(3)

COPYRIGHT

       2003-2025, The Open MPI Community

                                                  Feb 17, 2025                                SHMEM_INT_CSWAP(3)