1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
|
.\" -*- nroff -*-
.\" Copyright (c) 2015 University of Houston. All rights reserved.
.\" Copyright (c) 2015 Mellanox Technologies, Inc.
.\" $COPYRIGHT$
.de Vb
.ft CW
.nf
..
.de Ve
.ft R
.fi
..
.TH "SHMEM\\_PTR" "3" "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
.SH NAME
\fIshmem_ptr\fP(3)
\- Returns a pointer to a data object on a specified processing element
(PE).
.SH SYNOPSIS
C or C++:
.Vb
#include <mpp/shmem.h>
void *shmem_ptr(const void *target, int pe);
.Ve
Fortran:
.Vb
INCLUDE "mpp/shmem.fh"
POINTER (PTR, POINTEE)
INTEGER pe
PTR = SHMEM_PTR(target, pe)
.Ve
.SH DESCRIPTION
The shmem_ptr routine returns an address that can be used to directly reference
\fBtarget\fP
on the remote PE \fBpe\fP\&.
With this address we can perform ordinary loads
and stores to the remote address.
.PP
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
\fIshmem_put32\fP(3)
or \fIshmem_real_iget\fP(3),
the shmem_ptr function can
provide an efficient means to accomplish the communication.
.PP
The arguments are as follows:
.TP
target
The symmetric data object to be referenced.
.TP
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.
.PP
.SH EXAMPLES
This Fortran program calls shmem_ptr and then PE 0 writes to the BIGD array on PE 1:
.Vb
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
.Ve
This is the equivalent program written in C:
.Vb
#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");
}
}
.Ve
.SH NOTES
The shmem_ptr function is available only on systems where ordinary memory loads and
stores are used to implement SHMEM put and get operations.
.PP
.SH 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.
.PP
.SH SEE ALSO
\fIintro_shmem\fP(3),
\fIshmem_put\fP(3),
\fIshmem_get\fP(3)
.PP
|
