shmem_atomic_fetch_add

Performs an atomic fetch-and-add operation on a remote data object.

Definitions

C11 Synopsis

TYPE shmem_atomic_fetch_add(TYPE *dest, TYPE value, int pe);
TYPE shmem_atomic_fetch_add(shmem_ctx_t ctx, TYPE *dest, TYPE value, int pe);

where TYPE is one of the standard AMO types specified by Table:1

C/C++ Synopsis

TYPE shmem_TYPENAME_atomic_fetch_add(TYPE *dest, TYPE value, int pe);
TYPE shmem_ctx_TYPENAME_atomic_fetch_add(shmem_ctx_t ctx, TYPE *dest, TYPE value, int pe);

where TYPE is one of the standard AMO types and has a corresponding TYPENAME specified by Table:1

Deprecated Synopsis

Deprecated C11 Synopsis

TYPE shmem_fadd(TYPE *dest, TYPE value, int pe);

where TYPE is one of int, long, long long.

Deprecated C/C++ Synopsis

TYPE shmem_TYPENAME_fadd(TYPE *dest, TYPE value, int pe);

where TYPE is one of int, long, long long and has a corresponding TYPENAME specified by Table:1

Deprecated Fortran Synopsis

INTEGER pe
INTEGER*4 SHMEM_INT4_FADD, ires_i4, value_i4
ires_i4 = SHMEM_INT4_FADD(dest, value_i4, pe)
INTEGER*8 SHMEM_INT8_FADD, ires_i8, value_i8
ires_i8 = SHMEM_INT8_FADD(dest, value_i8, pe)

Datatype Reference Table

Table:1

|           TYPE          |      TYPENAME       |
|-------------------------|---------------------|
|   int                   |     int             |
|   long                  |     long            |
|   long long             |     longlong        |
|   unsigned int          |     uint            |
|   unsigned long         |     ulong           |
|   unsigned long long    |     ulonglong       |
|   int32_t               |     int32           |
|   int64_t               |     int64           |
|   uint32_t              |     uint32          |
|   uint64_t              |     uint64          |
|   size_t                |     size            |
|   ptrdiff_t             |     ptrdiff         |

Arguments

ctx     The context on which to perform the operation. When this argument is
        not provided, the operation is performed on SHMEM_CTX_DEFAULT.
dest    The remotely accessible integer data object to be updated on the
        remote PE. The type of dest should match that implied in the
        SYNOPSIS section.
value   The value to be atomically added to dest. The type of value
        should match that implied in the SYNOPSIS section.
pe      An integer that indicates the PE number on which dest is to be
        updated.  When using Fortran, it must be a default integer value.

Description

shmem_atomic_fetch_add routines perform an atomic fetch-and-add operation. An
atomic fetch-and-add operation fetches the old dest and adds value to dest
without the possibility of another atomic operation on the dest between the
time of the fetch and the update.  These routines add value to dest on pe and
return the previous contents of dest as an atomic operation.

When using Fortran, dest and value must be of the following type:
|     Routine      |Data type of dest and source|
|------------------|----------------------------|
| SHMEM_INT4_FADD  |      4-byte integer        |
| SHMEM_INT8_FADD  |      8-byte integer        |

Return Values

The contents that had been at the dest address on the remote PE prior to the
atomic addition operation.  The data type of the return value is the same as
the dest.

Notes

None.

Examples

C/C++ Example

The following shmem_atomic_fetch_add example is for C11 programs:

#include <stdio.h>
#include <shmem.h>

int main(void)
{
   int old = -1;
   static int dst = 22;
   shmem_init();
   int me = shmem_my_pe();
   if (me == 1)
      old = shmem_atomic_fetch_add(&dst, 44, 0);
   shmem_barrier_all();
   printf("%d: old = %d, dst = %d\n", me, old, dst);
   shmem_finalize();
   return 0;
}