18.2.178. shmem_ptr
shmem_ptr(3) - Returns a pointer to a data object on a specified processing element (PE).
18.2.178.1. SYNOPSIS
C or C++:
#include <mpp/shmem.h>
void *shmem_ptr(const void *target, int pe)
Fortran:
INCLUDE "mpp/shmem.fh"
POINTER (PTR, POINTEE)
INTEGER pe
PTR = SHMEM_PTR(target, pe)
18.2.178.2. DESCRIPTION
The shmem_ptr routine returns an address that can be used to directly reference target on the remote PE pe. With this address we can perform ordinary loads and stores to the remote address.
When a sequence of loads (gets) and stores (puts) to a data object on a remote PE does not match the access pattern provided in a SHMEM data transfer routine like shmem_put32(3) or shmem_real_iget(3), the shmem_ptr function can provide an efficient means to accomplish the communication.
The arguments are as follows:
- target
The symmetric data object to be referenced.
- pe
An integer that indicates the PE number on which target is to be accessed. If you are using Fortran, it must be a default integer value.
18.2.178.3. EXAMPLES
This Fortran program calls shmem_ptr and then PE 0 writes to the BIGD array on PE 1:
PROGRAM REMOTEWRITE
INCLUDE 'mpp/shmem.fh'
INTEGER BIGD(100)
SAVE BIGD
INTEGER POINTEE(*)
POINTER (PTR,POINTEE)
CALL START_PES(0)
IF (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 (MY_PE() .EQ. 1) THEN
PRINT *, 'BIGD on PE 1 is: '
PRINT *, BIGD
ENDIF
END
This is the equivalent program written in C:
#include <mpp/shmem.h>
main()
{
static int bigd[100];
int *ptr;
int i;
shmem_init();
if (shmem_my_pe() == 0) {
/* initialize PE 1's bigd array */
ptr = shmem_ptr(bigd, 1);
for (i=0; i<100; i++)
*ptr++ = i+1;
}
shmem_barrier_all();
if (shmem_my_pe() == 1) {
printf("bigd on PE 1 is:\n");
for (i=0; i<100; i++)
printf(" %d\n",bigd[i]);
printf("\n");
}
}