shmem_ptr

Returns a local pointer to a symmetric data object on the specified PE.

Definitions

C/C++ Synopsis

void *shmem_ptr(const void *dest, int pe);

Deprecated Synopsos

Deprecated Fortran Synopsis

POINTER (PTR, POINTEE)
INTEGER pe
PTR = SHMEM_PTR(dest, pe)

Arguments

dest    The symmetric data object to be referenced.
pe      An integer that indicates the PE number on which dest is to
        be accessed.  When using Fortran, it must be a  default integer
        value.

Description

shmem_ptr returns an address that may be used to directly reference dest
on the specified PE.  This address can be assigned to a pointer. After that,
ordinary loads and stores to this remote address may be performed.

The shmem_ptr routine can provide an efficient means to accomplish
communication, for example when a sequence of reads and writes to a data
object on a remote PE does not match the access pattern provided in an
OpenSHMEM data transfer routine like shmem_put or shmem_iget.

Return Values

The address of the dest data object is returned when it is accessible
using memory loads and stores.  Otherwise, a null pointer is returned.

Notes

When calling shmem_ptr, dest is the address of the referenced symmetric data
object on the calling PE.

Examples

Fortran Example

This  Fortran  program calls shmem_ptr and then PE 0 writes to the BIGD
array on PE 1:

PROGRAM REMOTEWRITE
INCLUDE "shmem.fh"

INTEGER BIGD(100)
SAVE BIGD

INTEGER POINTEE(*)
POINTER (PTR,POINTEE)

CALL SHMEM_INIT()

IF (SHMEM_MY_PE() .EQ. 0) THEN
   ! initialize PE 1's BIGD array
   PTR = SHMEM_PTR(BIGD, 1)     ! get address of PE 1's BIGD
                                !   array
   DO I=1,100
        POINTEE(I) = I
   ENDDO
ENDIF

CALL SHMEM_BARRIER_ALL

IF (SHMEM_MY_PE() .EQ. 1) THEN
   PRINT*,'BIGD on PE 1 is: '
   PRINT*,BIGD
ENDIF
END

C/C++ Example

This is the equivalent program written in C11:

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

int main(void)
{
   static int dest[4];
   shmem_init();
   int me = shmem_my_pe();
   if (me == 0) { /* initialize PE 1's dest array */
      int* ptr = shmem_ptr(dest, 1);
      if (ptr == NULL)
         printf("can't use pointer to directly access PE 1's dest array\n");
      else
         for (int i = 0; i < 4; i++)
            *ptr++ = i + 1;
   }
   shmem_barrier_all();
   if (me == 1)
      printf("PE 1 dest: %d, %d, %d, %d\n",
         dest[0], dest[1], dest[2], dest[3]);
   shmem_finalize();
   return 0;
}