modules/up/src/Core/gnu/MLCG.cc
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FUNCTIONS
This source file includes following functions.
- MLCG
- reset
- asLong
1 // This may look like C code, but it is really -*- C++ -*-
2 /*
3 Copyright (C) 1989 Free Software Foundation
4
5 This file is part of the GNU C++ Library. This library is free
6 software; you can redistribute it and/or modify it under the terms of
7 the GNU Library General Public License as published by the Free
8 Software Foundation; either version 2 of the License, or (at your
9 option) any later version. This library is distributed in the hope
10 that it will be useful, but WITHOUT ANY WARRANTY; without even the
11 implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
12 PURPOSE. See the GNU Library General Public License for more details.
13 You should have received a copy of the GNU Library General Public
14 License along with this library; if not, write to the Free Software
15 Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
16 */
17 #ifdef __GNUG__
18 #pragma implementation
19 #endif
20 #include "gnu/MLCG.h"
21 //
22 // SEED_TABLE_SIZE must be a power of 2
23 //
24
25
26 #define SEED_TABLE_SIZE 32
27
28 static _G_int32_t seedTable[SEED_TABLE_SIZE] = {
29 0xbdcc47e5, 0x54aea45d, 0xec0df859, 0xda84637b,
30 0xc8c6cb4f, 0x35574b01, 0x28260b7d, 0x0d07fdbf,
31 0x9faaeeb0, 0x613dd169, 0x5ce2d818, 0x85b9e706,
32 0xab2469db, 0xda02b0dc, 0x45c60d6e, 0xffe49d10,
33 0x7224fea3, 0xf9684fc9, 0xfc7ee074, 0x326ce92a,
34 0x366d13b5, 0x17aaa731, 0xeb83a675, 0x7781cb32,
35 0x4ec7c92d, 0x7f187521, 0x2cf346b4, 0xad13310f,
36 0xb89cff2b, 0x12164de1, 0xa865168d, 0x32b56cdf
37 };
38
39 MLCG::MLCG(_G_int32_t seed1, _G_int32_t seed2)
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40 {
41 initialSeedOne = seed1;
42 initialSeedTwo = seed2;
43 reset();
44 }
45
46 void
47 MLCG::reset()
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48 {
49 _G_int32_t seed1 = initialSeedOne;
50 _G_int32_t seed2 = initialSeedTwo;
51
52 //
53 // Most people pick stupid seed numbers that do not have enough
54 // bits. In this case, if they pick a small seed number, we
55 // map that to a specific seed.
56 //
57 if (seed1 < 0) {
58 seed1 = (seed1 + 2147483561);
59 seed1 = (seed1 < 0) ? -seed1 : seed1;
60 }
61
62 if (seed2 < 0) {
63 seed2 = (seed2 + 2147483561);
64 seed2 = (seed2 < 0) ? -seed2 : seed2;
65 }
66
67 if (seed1 > -1 && seed1 < SEED_TABLE_SIZE) {
68 seedOne = seedTable[seed1];
69 } else {
70 seedOne = seed1 ^ seedTable[seed1 & (SEED_TABLE_SIZE-1)];
71 }
72
73 if (seed2 > -1 && seed2 < SEED_TABLE_SIZE) {
74 seedTwo = seedTable[seed2];
75 } else {
76 seedTwo = seed2 ^ seedTable[ seed2 & (SEED_TABLE_SIZE-1) ];
77 }
78 seedOne = (seedOne % 2147483561) + 1;
79 seedTwo = (seedTwo % 2147483397) + 1;
80 }
81
82 _G_uint32_t MLCG::asLong()
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83 {
84 _G_int32_t k = seedOne % 53668;
85
86 seedOne = 40014 * (seedOne-k * 53668) - k * 12211;
87 if (seedOne < 0) {
88 seedOne += 2147483563;
89 }
90
91 k = seedTwo % 52774;
92 seedTwo = 40692 * (seedTwo - k * 52774) - k * 3791;
93 if (seedTwo < 0) {
94 seedTwo += 2147483399;
95 }
96
97 _G_int32_t z = seedOne - seedTwo;
98 if (z < 1) {
99 z += 2147483562;
100 }
101 return( (unsigned long) z);
102 }
103