SHMEM_CSWAP(3)SHMEM_CSWAP(3)NAME
shmem_int_cswap, shmem_int4_cswap, shmem_int8_cswap, shmem_long_cswap,
shmem_longlong_cswap - 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 shmem_longlong_cswap(longlong *target, longlong cond, longlong
value, int pe);
Fortran:
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 data type of
target should match that implied in the SYNOPSIS section.
If you are using Fortran, it must be of the following type:
Routine Data 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 on 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 exectute the
conditional swap will successfully write its PE number to race_winner
on PE 0.
main()
{
static int race_winner = -1;
int oldval;
start_pes(2);
oldval = shmem_int_cswap(&race_winner, -1, _my_pe(), 0);
if (oldval == -1) printf("pe %d was first\n",_my_pe());
}
SEE ALSOintro_shmem(3), shmem_cache(3), shmem_swap(3)
