SHMEM_PTR(3) Open MPI SHMEM_PTR(3)
NAME
shmem_ptr(3) - Returns a pointer to a data object on a specified pro-
cessing element (PE).
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)
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.
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");
}
}
NOTES
The shmem_ptr function is available only on systems where ordinary mem-
ory loads and stores are used to implement SHMEM put and get opera-
tions.
RETURN VALUES
shmem_ptr returns a pointer to the data object on the specified remote
PE. If target is not remotely accessible, a NULL pointer is returned.
SEE ALSO
intro_shmem(3), shmem_put(3), shmem_get(3)
4.1.2 Nov 24, 2021 SHMEM_PTR(3)
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