NAME

       shmem_int_cswap(3),    shmem_int4_cswap(3),    shmem_int8_cswap(3),   shmem_long_cswap(3),
       shmem_longlong_cswap(3) - Performs an atomic conditional swap to a remote data object

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)