44 lines
1.2 KiB
C
44 lines
1.2 KiB
C
/*
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* $Id$
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*
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Copyright 2006-2011 Chung, Hyung-Hwan.
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This file is part of QSE.
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QSE is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as
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published by the Free Software Foundation, either version 3 of
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the License, or (at your option) any later version.
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QSE 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
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with QSE. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <qse/cmn/alg.h>
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/* Park-Miller "minimal standard" 31 bit
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* pseudo-random number generator, implemented
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* with David G. Carta's optimisation: with
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* 32 bit math and wihtout division.
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*/
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qse_uint32_t qse_rand31 (qse_uint32_t seed)
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{
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qse_uint32_t hi, lo;
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if (seed == 0) seed++;
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lo = 16807 * (seed & 0xFFFF);
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hi = 16807 * (seed >> 16);
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lo += (hi & 0x7FFF) << 16;
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lo += hi >> 15;
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if (lo > 0x7FFFFFFFul) lo -= 0x7FFFFFFFul;
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return lo;
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}
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