42 lines
1.4 KiB
C
42 lines
1.4 KiB
C
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/*
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* Copyright (c) 2002-2006 Hewlett-Packard Development Company, L.P.
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* Contributed by David Mosberger-Tang <davidm@hpl.hp.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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* 02111-1307 USA
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*/
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#include <linux/types.h>
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#include <linux/module.h>
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/*
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* Fast, simple, yet decent quality random number generator based on
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* a paper by David G. Carta ("Two Fast Implementations of the
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* `Minimal Standard' Random Number Generator," Communications of the
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* ACM, January, 1990).
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*/
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u64 carta_random32 (u64 seed)
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{
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# define A 16807
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# define M ((u32) 1 << 31)
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u64 s, prod = A * seed, p, q;
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p = (prod >> 31) & (M - 1);
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q = (prod >> 0) & (M - 1);
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s = p + q;
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if (s >= M)
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s -= M - 1;
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return s;
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}
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EXPORT_SYMBOL_GPL(carta_random32);
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