ViewVC Help
View File | Revision Log | Show Annotations | View Changeset | Root Listing
root/group/trunk/OOPSE-2.0/src/math/MersenneTwister.hpp
Revision: 2204
Committed: Fri Apr 15 22:04:00 2005 UTC (19 years, 2 months ago) by gezelter
File size: 16332 byte(s)
Log Message:
xemacs has been drafted to perform our indentation services

File Contents

# Content
1 // MersenneTwister.h
2 // Mersenne Twister random number generator -- a C++ class MTRand
3 // Based on code by Makoto Matsumoto, Takuji Nishimura, and Shawn Cokus
4 // Richard J. Wagner v1.0 15 May 2003 rjwagner@writeme.com
5
6 // The Mersenne Twister is an algorithm for generating random numbers. It
7 // was designed with consideration of the flaws in various other generators.
8 // The period, 2^19937-1, and the order of equidistribution, 623 dimensions,
9 // are far greater. The generator is also fast; it avoids multiplication and
10 // division, and it benefits from caches and pipelines. For more information
11 // see the inventors' web page at http://www.math.keio.ac.jp/~matumoto/emt.html
12
13 // Reference
14 // M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-Dimensionally
15 // Equidistributed Uniform Pseudo-Random Number Generator", ACM Transactions on
16 // Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3-30.
17
18 // Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
19 // Copyright (C) 2000 - 2003, Richard J. Wagner
20 // All rights reserved.
21 //
22 // Redistribution and use in source and binary forms, with or without
23 // modification, are permitted provided that the following conditions
24 // are met:
25 //
26 // 1. Redistributions of source code must retain the above copyright
27 // notice, this list of conditions and the following disclaimer.
28 //
29 // 2. Redistributions in binary form must reproduce the above copyright
30 // notice, this list of conditions and the following disclaimer in the
31 // documentation and/or other materials provided with the distribution.
32 //
33 // 3. The names of its contributors may not be used to endorse or promote
34 // products derived from this software without specific prior written
35 // permission.
36 //
37 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
38 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
39 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
40 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
41 // CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
42 // EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
43 // PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
44 // PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
45 // LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
46 // NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
47 // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
48
49 // The original code included the following notice:
50 //
51 // When you use this, send an email to: matumoto@math.keio.ac.jp
52 // with an appropriate reference to your work.
53 //
54 // It would be nice to CC: rjwagner@writeme.com and Cokus@math.washington.edu
55 // when you write.
56
57 #ifndef MERSENNETWISTER_H
58 #define MERSENNETWISTER_H
59
60 // Not thread safe (unless auto-initialization is avoided and each thread has
61 // its own MTRand object)
62
63 #include <cassert>
64 #include <iostream>
65 #include <limits.h>
66 #include <stdio.h>
67 #include <time.h>
68 #include <math.h>
69 #include <vector>
70 namespace oopse {
71
72 class MTRand {
73 // Data
74 public:
75 typedef unsigned long uint32; // unsigned integer type, at least 32 bits
76
77 enum { N = 624 }; // length of state vector
78 enum { SAVE = N + 1 }; // length of array for save()
79
80 private:
81 enum { M = 397 }; // period parameter
82
83 uint32 state[N]; // internal state
84 uint32 *pNext; // next value to get from state
85 int left; // number of values left before reload needed
86 int nstrides_;
87 int stride_;
88
89 //Methods
90 public:
91 MTRand( const uint32& oneSeed, int nstrides, int stride); // initialize with a simple uint32
92 MTRand( uint32 *const bigSeed, uint32 const seedLength, int nstrides, int stride); // or an array
93 MTRand(int nstrides, int stride); // auto-initialize with /dev/urandom or time() and clock()
94
95 // Do NOT use for CRYPTOGRAPHY without securely hashing several returned
96 // values together, otherwise the generator state can be learned after
97 // reading 624 consecutive values.
98
99 // Access to 32-bit random numbers
100 double rand(); // real number in [0,1]
101 double rand( const double& n ); // real number in [0,n]
102 double randExc(); // real number in [0,1)
103 double randExc( const double& n ); // real number in [0,n)
104 double randDblExc(); // real number in (0,1)
105 double randDblExc( const double& n ); // real number in (0,n)
106 uint32 randInt(); // integer in [0,2^32-1] (modified for striding)
107 uint32 rawRandInt(); // original randInt
108 uint32 randInt( const uint32& n ); // integer in [0,n] for n < 2^32
109 double operator()() { return rand(); } // same as rand()
110
111 // Access to 53-bit random numbers (capacity of IEEE double precision)
112 double rand53(); // real number in [0,1)
113
114 // Access to nonuniform random number distributions
115 double randNorm( const double& mean = 0.0, const double& variance = 0.0 );
116
117 // Re-seeding functions with same behavior as initializers
118 void seed( const uint32 oneSeed );
119 void seed( uint32 *const bigSeed, const uint32 seedLength = N );
120 void seed();
121
122 std::vector<uint32>generateSeeds();
123
124 // Saving and loading generator state
125 void save( uint32* saveArray ) const; // to array of size SAVE
126 void load( uint32 *const loadArray ); // from such array
127 friend std::ostream& operator<<( std::ostream& os, const MTRand& mtrand );
128 friend std::istream& operator>>( std::istream& is, MTRand& mtrand );
129
130 protected:
131 void initialize( const uint32 oneSeed );
132 void reload();
133 uint32 hiBit( const uint32& u ) const { return u & 0x80000000UL; }
134 uint32 loBit( const uint32& u ) const { return u & 0x00000001UL; }
135 uint32 loBits( const uint32& u ) const { return u & 0x7fffffffUL; }
136 uint32 mixBits( const uint32& u, const uint32& v ) const
137 { return hiBit(u) | loBits(v); }
138 uint32 twist( const uint32& m, const uint32& s0, const uint32& s1 ) const
139 { return m ^ (mixBits(s0,s1)>>1) ^ (-loBit(s1) & 0x9908b0dfUL); }
140 static uint32 hash( time_t t, clock_t c );
141 };
142
143
144 inline MTRand::MTRand( const uint32& oneSeed, int nstrides, int stride) : nstrides_(nstrides), stride_(stride) {
145 assert(stride_ < nstrides_ && stride_ >= 0);
146 seed(oneSeed);
147 }
148
149 inline MTRand::MTRand( uint32 *const bigSeed, const uint32 seedLength, int nstrides, int stride) : nstrides_(nstrides), stride_(stride) {
150 assert(stride_ < nstrides_ && stride_ >= 0);
151 seed(bigSeed,seedLength);
152 }
153
154 inline MTRand::MTRand(int nstrides, int stride) : nstrides_(nstrides), stride_(stride){
155 assert(stride_ < nstrides_ && stride_ >= 0);
156 seed();
157 }
158
159 inline double MTRand::rand()
160 { return double(randInt()) * (1.0/4294967295.0); }
161
162 inline double MTRand::rand( const double& n )
163 { return rand() * n; }
164
165 inline double MTRand::randExc()
166 { return double(randInt()) * (1.0/4294967296.0); }
167
168 inline double MTRand::randExc( const double& n )
169 { return randExc() * n; }
170
171 inline double MTRand::randDblExc()
172 { return ( double(randInt()) + 0.5 ) * (1.0/4294967296.0); }
173
174 inline double MTRand::randDblExc( const double& n )
175 { return randDblExc() * n; }
176
177 inline double MTRand::rand53()
178 {
179 uint32 a = randInt() >> 5, b = randInt() >> 6;
180 return ( a * 67108864.0 + b ) * (1.0/9007199254740992.0); // by Isaku Wada
181 }
182
183 inline double MTRand::randNorm( const double& mean, const double& variance )
184 {
185 // Return a real number from a normal (Gaussian) distribution with given
186 // mean and variance by Box-Muller method
187 double r = sqrt( -2.0 * log( 1.0-randDblExc()) ) * variance;
188 double phi = 2.0 * 3.14159265358979323846264338328 * randExc();
189 return mean + r * cos(phi);
190 }
191
192 /**
193 * This function is modified from the original to allow for random
194 * streams on parallel jobs. It now takes numbers from by striding
195 * through the random stream and picking up only one of the random
196 * numbers per nstrides_. The number it picks is the stride_'th
197 * number in the stride sequence.
198 */
199 inline MTRand::uint32 MTRand::randInt() {
200
201 std::vector<uint32> ranNums(nstrides_);
202
203 for (int i = 0; i < nstrides_; ++i) {
204 ranNums[i] = rawRandInt();
205 }
206
207 return ranNums[stride_];
208 }
209
210 /**
211 * This is the original randInt function which implements the mersenne
212 * twister.
213 */
214 inline MTRand::uint32 MTRand::rawRandInt()
215 {
216 // Pull a 32-bit integer from the generator state
217 // Every other access function simply transforms the numbers extracted here
218
219 if( left == 0 ) reload();
220 --left;
221
222 register uint32 s1;
223 s1 = *pNext++;
224 s1 ^= (s1 >> 11);
225 s1 ^= (s1 << 7) & 0x9d2c5680UL;
226 s1 ^= (s1 << 15) & 0xefc60000UL;
227 return ( s1 ^ (s1 >> 18) );
228 }
229
230 inline MTRand::uint32 MTRand::randInt( const uint32& n )
231 {
232 // Find which bits are used in n
233 // Optimized by Magnus Jonsson (magnus@smartelectronix.com)
234 uint32 used = n;
235 used |= used >> 1;
236 used |= used >> 2;
237 used |= used >> 4;
238 used |= used >> 8;
239 used |= used >> 16;
240
241 // Draw numbers until one is found in [0,n]
242 uint32 i;
243 do
244 i = randInt() & used; // toss unused bits to shorten search
245 while( i > n );
246 return i;
247 }
248
249
250 inline void MTRand::seed( const uint32 oneSeed )
251 {
252 // Seed the generator with a simple uint32
253 initialize(oneSeed);
254 reload();
255 }
256
257
258 inline void MTRand::seed( uint32 *const bigSeed, const uint32 seedLength )
259 {
260 // Seed the generator with an array of uint32's
261 // There are 2^19937-1 possible initial states. This function allows
262 // all of those to be accessed by providing at least 19937 bits (with a
263 // default seed length of N = 624 uint32's). Any bits above the lower 32
264 // in each element are discarded.
265 // Just call seed() if you want to get array from /dev/urandom
266 initialize(19650218UL);
267 register int i = 1;
268 register uint32 j = 0;
269 register int k = ( N > seedLength ? N : seedLength );
270 for( ; k; --k )
271 {
272 state[i] =
273 state[i] ^ ( (state[i-1] ^ (state[i-1] >> 30)) * 1664525UL );
274 state[i] += ( bigSeed[j] & 0xffffffffUL ) + j;
275 state[i] &= 0xffffffffUL;
276 ++i; ++j;
277 if( i >= N ) { state[0] = state[N-1]; i = 1; }
278 if( j >= seedLength ) j = 0;
279 }
280 for( k = N - 1; k; --k )
281 {
282 state[i] =
283 state[i] ^ ( (state[i-1] ^ (state[i-1] >> 30)) * 1566083941UL );
284 state[i] -= i;
285 state[i] &= 0xffffffffUL;
286 ++i;
287 if( i >= N ) { state[0] = state[N-1]; i = 1; }
288 }
289 state[0] = 0x80000000UL; // MSB is 1, assuring non-zero initial array
290 reload();
291 }
292
293
294 inline void MTRand::seed()
295 {
296 std::vector<uint32> seeds;
297
298 seeds = generateSeeds();
299
300 if (seeds.size() == 1) {
301 seed( seeds[0] );
302 } else {
303 seed( &seeds[0], seeds.size() );
304 }
305 }
306
307
308 inline std::vector<MTRand::uint32> MTRand::generateSeeds() {
309 // Seed the generator with an array from /dev/urandom if available
310 // Otherwise use a hash of time() and clock() values
311
312 std::vector<uint32> bigSeed;
313
314 // First try getting an array from /dev/urandom
315 FILE* urandom = fopen( "/dev/urandom", "rb" );
316 if( urandom )
317 {
318 bigSeed.resize(N);
319 register uint32 *s = &bigSeed[0];
320 register int i = N;
321 register bool success = true;
322 while( success && i-- )
323 success = fread( s++, sizeof(uint32), 1, urandom );
324 fclose(urandom);
325 if( success ) { return bigSeed; }
326 }
327
328 // Was not successful, so use time() and clock() instead
329
330 bigSeed.push_back(hash( time(NULL), clock()));
331 return bigSeed;
332 }
333
334
335 inline void MTRand::initialize( const uint32 seed )
336 {
337 // Initialize generator state with seed
338 // See Knuth TAOCP Vol 2, 3rd Ed, p.106 for multiplier.
339 // In previous versions, most significant bits (MSBs) of the seed affect
340 // only MSBs of the state array. Modified 9 Jan 2002 by Makoto Matsumoto.
341 register uint32 *s = state;
342 register uint32 *r = state;
343 register int i = 1;
344 *s++ = seed & 0xffffffffUL;
345 for( ; i < N; ++i )
346 {
347 *s++ = ( 1812433253UL * ( *r ^ (*r >> 30) ) + i ) & 0xffffffffUL;
348 r++;
349 }
350 }
351
352
353 inline void MTRand::reload()
354 {
355 // Generate N new values in state
356 // Made clearer and faster by Matthew Bellew (matthew.bellew@home.com)
357 register uint32 *p = state;
358 register int i;
359 for( i = N - M; i--; ++p )
360 *p = twist( p[M], p[0], p[1] );
361 for( i = M; --i; ++p )
362 *p = twist( p[M-N], p[0], p[1] );
363 *p = twist( p[M-N], p[0], state[0] );
364
365 left = N, pNext = state;
366 }
367
368
369 inline MTRand::uint32 MTRand::hash( time_t t, clock_t c )
370 {
371 // Get a uint32 from t and c
372 // Better than uint32(x) in case x is floating point in [0,1]
373 // Based on code by Lawrence Kirby (fred@genesis.demon.co.uk)
374
375 static uint32 differ = 0; // guarantee time-based seeds will change
376
377 uint32 h1 = 0;
378 unsigned char *p = (unsigned char *) &t;
379 for( size_t i = 0; i < sizeof(t); ++i )
380 {
381 h1 *= UCHAR_MAX + 2U;
382 h1 += p[i];
383 }
384 uint32 h2 = 0;
385 p = (unsigned char *) &c;
386 for( size_t j = 0; j < sizeof(c); ++j )
387 {
388 h2 *= UCHAR_MAX + 2U;
389 h2 += p[j];
390 }
391 return ( h1 + differ++ ) ^ h2;
392 }
393
394
395 inline void MTRand::save( uint32* saveArray ) const
396 {
397 register uint32 *sa = saveArray;
398 register const uint32 *s = state;
399 register int i = N;
400 for( ; i--; *sa++ = *s++ ) {}
401 *sa = left;
402 }
403
404
405 inline void MTRand::load( uint32 *const loadArray )
406 {
407 register uint32 *s = state;
408 register uint32 *la = loadArray;
409 register int i = N;
410 for( ; i--; *s++ = *la++ ) {}
411 left = *la;
412 pNext = &state[N-left];
413 }
414
415
416 inline std::ostream& operator<<( std::ostream& os, const MTRand& mtrand )
417 {
418 register const MTRand::uint32 *s = mtrand.state;
419 register int i = mtrand.N;
420 for( ; i--; os << *s++ << "\t" ) {}
421 return os << mtrand.left;
422 }
423
424
425 inline std::istream& operator>>( std::istream& is, MTRand& mtrand )
426 {
427 register MTRand::uint32 *s = mtrand.state;
428 register int i = mtrand.N;
429 for( ; i--; is >> *s++ ) {}
430 is >> mtrand.left;
431 mtrand.pNext = &mtrand.state[mtrand.N-mtrand.left];
432 return is;
433 }
434
435 }
436 #endif // MERSENNETWISTER_H
437
438 // Change log:
439 //
440 // v0.1 - First release on 15 May 2000
441 // - Based on code by Makoto Matsumoto, Takuji Nishimura, and Shawn Cokus
442 // - Translated from C to C++
443 // - Made completely ANSI compliant
444 // - Designed convenient interface for initialization, seeding, and
445 // obtaining numbers in default or user-defined ranges
446 // - Added automatic seeding from /dev/urandom or time() and clock()
447 // - Provided functions for saving and loading generator state
448 //
449 // v0.2 - Fixed bug which reloaded generator one step too late
450 //
451 // v0.3 - Switched to clearer, faster reload() code from Matthew Bellew
452 //
453 // v0.4 - Removed trailing newline in saved generator format to be consistent
454 // with output format of built-in types
455 //
456 // v0.5 - Improved portability by replacing static const int's with enum's and
457 // clarifying return values in seed(); suggested by Eric Heimburg
458 // - Removed MAXINT constant; use 0xffffffffUL instead
459 //
460 // v0.6 - Eliminated seed overflow when uint32 is larger than 32 bits
461 // - Changed integer [0,n] generator to give better uniformity
462 //
463 // v0.7 - Fixed operator precedence ambiguity in reload()
464 // - Added access for real numbers in (0,1) and (0,n)
465 //
466 // v0.8 - Included time.h header to properly support time_t and clock_t
467 //
468 // v1.0 - Revised seeding to match 26 Jan 2002 update of Nishimura and Matsumoto
469 // - Allowed for seeding with arrays of any length
470 // - Added access for real numbers in [0,1) with 53-bit resolution
471 // - Added access for real numbers from normal (Gaussian) distributions
472 // - Increased overall speed by optimizing twist()
473 // - Doubled speed of integer [0,n] generation
474 // - Fixed out-of-range number generation on 64-bit machines
475 // - Improved portability by substituting literal constants for long enum's
476 // - Changed license from GNU LGPL to BSD