/[svn]/ircd-hybrid-7.2/src/rng_mt.c
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Contents of /ircd-hybrid-7.2/src/rng_mt.c

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Revision 982 - (show annotations)
Thu Aug 13 22:15:08 2009 UTC (11 years, 6 months ago) by michael
File MIME type: text/x-chdr
File size: 4979 byte(s)
- added a mersenne twister basedn prng

1 /*
2 A C-program for MT19937, with initialization improved 2002/1/26.
3 Coded by Takuji Nishimura and Makoto Matsumoto.
4
5 Before using, initialize the state by using init_genrand(seed)
6 or init_by_array(init_key, key_length).
7
8 Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
9 All rights reserved.
10
11 Redistribution and use in source and binary forms, with or without
12 modification, are permitted provided that the following conditions
13 are met:
14
15 1. Redistributions of source code must retain the above copyright
16 notice, this list of conditions and the following disclaimer.
17
18 2. Redistributions in binary form must reproduce the above copyright
19 notice, this list of conditions and the following disclaimer in the
20 documentation and/or other materials provided with the distribution.
21
22 3. The names of its contributors may not be used to endorse or promote
23 products derived from this software without specific prior written
24 permission.
25
26 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
27 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
28 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
29 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
30 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31 EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32 PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33 PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34 LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35 NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36 SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37
38
39 Any feedback is very welcome.
40 http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
41 email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space)
42
43 $Id$
44 */
45
46 #include "rng_mt.h"
47
48 /* Period parameters */
49 #define N 624
50 #define M 397
51 #define MATRIX_A 0x9908b0dfUL /* constant vector a */
52 #define UPPER_MASK 0x80000000UL /* most significant w-r bits */
53 #define LOWER_MASK 0x7fffffffUL /* least significant r bits */
54
55 static unsigned long mt[N]; /* the array for the state vector */
56 static int mti = N + 1; /* mti==N+1 means mt[N] is not initialized */
57
58 /* initializes mt[N] with a seed */
59 void
60 init_genrand(unsigned long s)
61 {
62 mt[0] = s & 0xffffffffUL;
63
64 for (mti = 1; mti < N; mti++)
65 {
66 mt[mti] = (1812433253UL * (mt[mti - 1] ^ (mt[mti - 1] >> 30)) + mti);
67 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
68 /* In the previous versions, MSBs of the seed affect */
69 /* only MSBs of the array mt[]. */
70 /* 2002/01/09 modified by Makoto Matsumoto */
71 mt[mti] &= 0xffffffffUL;
72 /* for >32 bit machines */
73 }
74 }
75
76 /* initialize by an array with array-length */
77 /* init_key is the array for initializing keys */
78 /* key_length is its length */
79 /* slight change for C++, 2004/2/26 */
80 void
81 init_by_array(unsigned long init_key[], int key_length)
82 {
83 int i, j, k;
84
85 init_genrand(19650218UL);
86
87 i = 1; j = 0;
88 k = (N > key_length ? N : key_length);
89
90 for (; k; k--)
91 {
92 mt[i] = (mt[i] ^ ((mt[i - 1] ^ (mt[i - 1] >> 30)) * 1664525UL))
93 + init_key[j] + j; /* non linear */
94 mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
95 i++; j++;
96
97 if (i >= N)
98 {
99 mt[0] = mt[N - 1];
100 i = 1;
101 }
102
103 if (j >= key_length)
104 j = 0;
105 }
106
107 for (k = N - 1; k; k--)
108 {
109 mt[i] = (mt[i] ^ ((mt[i - 1] ^ (mt[i - 1] >> 30)) * 1566083941UL))
110 - i; /* non linear */
111 mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
112 i++;
113
114 if (i >= N)
115 {
116 mt[0] = mt[N - 1];
117 i = 1;
118 }
119 }
120
121 mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
122 }
123
124 /* generates a random number on [0,0xffffffff]-interval */
125 unsigned long
126 genrand_int32(void)
127 {
128 unsigned long y;
129 static unsigned long mag01[2]={ 0x0UL, MATRIX_A };
130 /* mag01[x] = x * MATRIX_A for x=0,1 */
131
132 if (mti >= N)
133 { /* generate N words at one time */
134 int kk;
135
136 if (mti == N + 1) /* if init_genrand() has not been called, */
137 init_genrand(5489UL); /* a default initial seed is used */
138
139 for (kk = 0; kk < N - M; kk++)
140 {
141 y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
142 mt[kk] = mt[kk + M] ^ (y >> 1) ^ mag01[y & 0x1UL];
143 }
144
145 for (; kk < N - 1; kk++)
146 {
147 y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
148 mt[kk] = mt[kk + (M - N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
149 }
150
151 y = (mt[N - 1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
152 mt[N - 1] = mt[M - 1] ^ (y >> 1) ^ mag01[y & 0x1UL];
153
154 mti = 0;
155 }
156
157 y = mt[mti++];
158
159 /* Tempering */
160 y ^= (y >> 11);
161 y ^= (y << 7) & 0x9d2c5680UL;
162 y ^= (y << 15) & 0xefc60000UL;
163 y ^= (y >> 18);
164
165 return y;
166 }

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