128 строки
3.4 KiB
Plaintext
128 строки
3.4 KiB
Plaintext
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.\" -*- 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\\_CSWAP" "3" "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
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.SH NAME
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\fIshmem_int_cswap\fP(3),
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\fIshmem_int4_cswap\fP(3),
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\fIshmem_int8_cswap\fP(3),
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\fIshmem_long_cswap\fP(3),
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\fIshmem_longlong_cswap\fP(3)
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\- Performs an atomic conditional swap to a remote data object
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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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int shmem_int_cswap(int *target, int cond, int value, int pe);
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long shmem_long_cswap(long *target, long cond, long value,
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int pe);
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long long shmem_longlong_cswap(longlong *target,
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longlong cond, longlong value, 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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INTEGER pe
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INTEGER(KIND=4) SHMEM_INT4_CSWAP
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ires = SHMEM_INT4_CSWAP(target, cond, value, pe)
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INTEGER(KIND=8) SHMEM_INT8_CSWAP
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ires = SHMEM_INT8_CSWAP(target, cond, value, pe)
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.Ve
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.SH DESCRIPTION
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The conditional swap routines conditionally update a target data object on an arbitrary
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processing element (PE) and return the prior contents of the data object in one atomic
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operation.
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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 remotely accessible integer data object to be updated on the remote PE. If
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you are using C/C++, the type of target should match that implied in the SYNOPSIS section. If
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you are using the Fortran compiler, it must be of type integer with an element size of 4 bytes
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for SHMEM_INT4_ADD and 8 bytes for SHMEM_INT8_ADD.
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.TP
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value
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The value to be atomically added to target. If you are using C/C++, the type of
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value should match that implied in the SYNOPSIS section. If you are using Fortran, it must be
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of type integer with an element size of target.
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.TP
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pe
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An integer that indicates the PE number upon which target is to be updated. If you
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are using Fortran, it must be a default integer value.
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.TP
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target
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The remotely accessible integer data object to be updated on the remote PE. If
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you are using C/C++, the data type of target should match that implied in the SYNOPSIS
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section. If you are using Fortran, it must be of the following type:
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.RS
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.TP
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\fBSHMEM_INT4_CSWAP\fP: 4\-byte integer
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.TP
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\fBSHMEM_INT8_CSWAP\fP: 8\-byte integer
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.RE
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.RS
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.PP
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.RE
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.TP
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cond
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cond is compared to the remote target value. If cond and the remote target are
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equal, then value is swapped into the remote target. Otherwise, the remote target is
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unchanged. In either case, the old value of the remote target is returned as the function return
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value. cond must be of the same data type as target.
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.TP
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value
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The value to be atomically written to the remote PE. value must be the same data
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type as target.
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.TP
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pe
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An integer that indicates the PE number upon which target is to be updated. 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 NOTES
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The term remotely accessible is defined in \fIintro_shmem\fP(3)\&.
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.SH RETURN VALUES
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The contents that had been in the target data object on the remote PE prior to the conditional
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swap.
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.SH EXAMPLES
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The following call ensures that the first PE to execute the conditional swap will successfully
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write its PE number to race_winner on PE 0.
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.Vb
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main()
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{
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static int race_winner = \-1;
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int oldval;
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start_pes(2);
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oldval = shmem_int_cswap(&race_winner, \-1, _my_pe(), 0);
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if (oldval == \-1)
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printf("pe %d was first\\n",_my_pe());
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}
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.Ve
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.SH SEE ALSO
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\fIintro_shmem\fP(3),
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\fIshmem_cache\fP(3),
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\fIshmem_swap\fP(3)
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