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103 lines
2.8 KiB
C++
103 lines
2.8 KiB
C++
// This may look like C code, but it is really -*- C++ -*-
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/*
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Copyright (C) 1989 Free Software Foundation
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This file is part of the GNU C++ Library. This library is free
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software; you can redistribute it and/or modify it under the terms of
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the GNU Library General Public License as published by the Free
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Software Foundation; either version 2 of the License, or (at your
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option) any later version. This library is distributed in the hope
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that it will be useful, but WITHOUT ANY WARRANTY; without even the
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implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
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PURPOSE. See the GNU Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with this library; if not, write to the Free Software
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Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifdef __GNUG__
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#pragma implementation
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#endif
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#include <MLCG.h>
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//
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// SEED_TABLE_SIZE must be a power of 2
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//
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#define SEED_TABLE_SIZE 32
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static _G_int32_t seedTable[SEED_TABLE_SIZE] = {
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0xbdcc47e5, 0x54aea45d, 0xec0df859, 0xda84637b,
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0xc8c6cb4f, 0x35574b01, 0x28260b7d, 0x0d07fdbf,
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0x9faaeeb0, 0x613dd169, 0x5ce2d818, 0x85b9e706,
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0xab2469db, 0xda02b0dc, 0x45c60d6e, 0xffe49d10,
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0x7224fea3, 0xf9684fc9, 0xfc7ee074, 0x326ce92a,
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0x366d13b5, 0x17aaa731, 0xeb83a675, 0x7781cb32,
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0x4ec7c92d, 0x7f187521, 0x2cf346b4, 0xad13310f,
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0xb89cff2b, 0x12164de1, 0xa865168d, 0x32b56cdf
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};
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MLCG::MLCG(_G_int32_t seed1, _G_int32_t seed2)
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{
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initialSeedOne = seed1;
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initialSeedTwo = seed2;
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reset();
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}
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void
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MLCG::reset()
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{
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_G_int32_t seed1 = initialSeedOne;
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_G_int32_t seed2 = initialSeedTwo;
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//
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// Most people pick stupid seed numbers that do not have enough
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// bits. In this case, if they pick a small seed number, we
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// map that to a specific seed.
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//
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if (seed1 < 0) {
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seed1 = (seed1 + 2147483561);
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seed1 = (seed1 < 0) ? -seed1 : seed1;
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}
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if (seed2 < 0) {
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seed2 = (seed2 + 2147483561);
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seed2 = (seed2 < 0) ? -seed2 : seed2;
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}
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if (seed1 > -1 && seed1 < SEED_TABLE_SIZE) {
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seedOne = seedTable[seed1];
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} else {
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seedOne = seed1 ^ seedTable[seed1 & (SEED_TABLE_SIZE-1)];
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}
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if (seed2 > -1 && seed2 < SEED_TABLE_SIZE) {
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seedTwo = seedTable[seed2];
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} else {
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seedTwo = seed2 ^ seedTable[ seed2 & (SEED_TABLE_SIZE-1) ];
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}
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seedOne = (seedOne % 2147483561) + 1;
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seedTwo = (seedTwo % 2147483397) + 1;
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}
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_G_uint32_t MLCG::asLong()
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{
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_G_int32_t k = seedOne % 53668;
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seedOne = 40014 * (seedOne-k * 53668) - k * 12211;
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if (seedOne < 0) {
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seedOne += 2147483563;
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}
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k = seedTwo % 52774;
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seedTwo = 40692 * (seedTwo - k * 52774) - k * 3791;
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if (seedTwo < 0) {
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seedTwo += 2147483399;
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}
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_G_int32_t z = seedOne - seedTwo;
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if (z < 1) {
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z += 2147483562;
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}
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return( (unsigned long) z);
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}
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