130 строки
2.8 KiB
Plaintext
130 строки
2.8 KiB
Plaintext
.\" -*- nroff -*-
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.\" Copyright (c) 2015 University of Houston. All rights reserved.
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.\" Copyright (c) 2015 Mellanox Technologies, Inc.
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.\" $COPYRIGHT$
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.de Vb
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.ft CW
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.nf
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..
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.de Ve
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.ft R
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.fi
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..
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.TH "SHMEM\\_PTR" "3" "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fIshmem_ptr\fP(3)
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\- Returns a pointer to a data object on a specified processing element
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(PE).
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.SH SYNOPSIS
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C or C++:
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.Vb
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#include <mpp/shmem.h>
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void *shmem_ptr(const void *target, int pe);
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.Ve
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Fortran:
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.Vb
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INCLUDE "mpp/shmem.fh"
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POINTER (PTR, POINTEE)
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INTEGER pe
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PTR = SHMEM_PTR(target, pe)
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.Ve
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.SH DESCRIPTION
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The shmem_ptr routine returns an address that can be used to directly reference
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\fBtarget\fP
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on the remote PE \fBpe\fP\&.
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With this address we can perform ordinary loads
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and stores to the remote address.
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.PP
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When a sequence of loads (gets) and stores (puts) to a data object on a remote PE does not
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match the access pattern provided in a SHMEM data transfer routine like
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\fIshmem_put32\fP(3)
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or \fIshmem_real_iget\fP(3),
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the shmem_ptr function can
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provide an efficient means to accomplish the communication.
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.PP
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The arguments are as follows:
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.TP
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target
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The symmetric data object to be referenced.
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.TP
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pe
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An integer that indicates the PE number on which target is to be accessed. If you
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are using Fortran, it must be a default integer value.
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.PP
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.SH EXAMPLES
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This Fortran program calls shmem_ptr and then PE 0 writes to the BIGD array on PE 1:
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.Vb
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PROGRAM REMOTEWRITE
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INCLUDE 'mpp/shmem.fh'
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INTEGER BIGD(100)
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SAVE BIGD
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INTEGER POINTEE(*)
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POINTER (PTR,POINTEE)
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CALL START_PES(0)
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IF (MY_PE() .EQ. 0) THEN
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! initialize PE 1's BIGD array
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PTR = SHMEM_PTR(BIGD, 1) ! get address of PE 1's BIGD
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! array
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DO I=1,100
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POINTEE(I) = I
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ENDDO
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ENDIF
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CALL SHMEM_BARRIER_ALL
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IF (MY_PE() .EQ. 1) THEN
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PRINT *, 'BIGD on PE 1 is: '
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PRINT *, BIGD
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ENDIF
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END
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.Ve
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This is the equivalent program written in C:
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.Vb
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#include <mpp/shmem.h>
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main()
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{
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static int bigd[100];
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int *ptr;
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int i;
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shmem_init();
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if (shmem_my_pe() == 0) {
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/* initialize PE 1's bigd array */
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ptr = shmem_ptr(bigd, 1);
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for (i=0; i<100; i++)
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*ptr++ = i+1;
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}
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shmem_barrier_all();
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if (shmem_my_pe() == 1) {
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printf("bigd on PE 1 is:\\n");
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for (i=0; i<100; i++)
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printf(" %d\\n",bigd[i]);
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printf("\\n");
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}
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}
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.Ve
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.SH NOTES
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The shmem_ptr function is available only on systems where ordinary memory loads and
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stores are used to implement SHMEM put and get operations.
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.PP
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.SH RETURN VALUES
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shmem_ptr returns a pointer to the data object on the specified remote PE. If target is not
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remotely accessible, a NULL pointer is returned.
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.PP
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.SH SEE ALSO
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\fIintro_shmem\fP(3),
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\fIshmem_put\fP(3),
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\fIshmem_get\fP(3)
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.PP
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