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/* |
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I've wrapped Makoto Matsumoto and Takuji Nishimura's code in a namespace |
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so it's better encapsulated. Now you can have multiple random number generators |
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and they won't stomp all over eachother's state. |
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If you want to use this as a substitute for Math.random(), use the random() |
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method like so: |
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var m = new MersenneTwister(); |
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var randomNumber = m.random(); |
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You can also call the other genrand_{foo}() methods on the instance. |
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If you want to use a specific seed in order to get a repeatable random |
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sequence, pass an integer into the constructor: |
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var m = new MersenneTwister(123); |
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and that will always produce the same random sequence. |
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Sean McCullough (banksean@gmail.com) |
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*/ |
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/* |
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A C-program for MT19937, with initialization improved 2002/1/26. |
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Coded by Takuji Nishimura and Makoto Matsumoto. |
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Before using, initialize the state by using init_genrand(seed) |
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or init_by_array(init_key, key_length). |
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Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura, |
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All rights reserved. |
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Redistribution and use in source and binary forms, with or without |
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modification, are permitted provided that the following conditions |
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are met: |
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1. Redistributions of source code must retain the above copyright |
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notice, this list of conditions and the following disclaimer. |
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2. Redistributions in binary form must reproduce the above copyright |
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notice, this list of conditions and the following disclaimer in the |
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documentation and/or other materials provided with the distribution. |
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3. The names of its contributors may not be used to endorse or promote |
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products derived from this software without specific prior written |
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permission. |
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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Any feedback is very welcome. |
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http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html |
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email: m-mat @ math.sci.hiroshima-u.ac.jp (remove space) |
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*/ |
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var MersenneTwister = function(seed) { |
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if (seed == undefined) { |
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seed = new Date().getTime(); |
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} |
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/* Period parameters */ |
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this.N = 624; |
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this.M = 397; |
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this.MATRIX_A = 0x9908b0df; /* constant vector a */ |
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this.UPPER_MASK = 0x80000000; /* most significant w-r bits */ |
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this.LOWER_MASK = 0x7fffffff; /* least significant r bits */ |
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this.mt = new Array(this.N); /* the array for the state vector */ |
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this.mti=this.N+1; /* mti==N+1 means mt[N] is not initialized */ |
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this.init_genrand(seed); |
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} |
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/* initializes mt[N] with a seed */ |
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MersenneTwister.prototype.init_genrand = function(s) { |
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this.mt[0] = s >>> 0; |
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for (this.mti=1; this.mti<this.N; this.mti++) { |
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var s = this.mt[this.mti-1] ^ (this.mt[this.mti-1] >>> 30); |
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this.mt[this.mti] = (((((s & 0xffff0000) >>> 16) * 1812433253) << 16) + (s & 0x0000ffff) * 1812433253) |
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+ this.mti; |
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/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */ |
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/* In the previous versions, MSBs of the seed affect */ |
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/* only MSBs of the array mt[]. */ |
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/* 2002/01/09 modified by Makoto Matsumoto */ |
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this.mt[this.mti] >>>= 0; |
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/* for >32 bit machines */ |
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} |
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} |
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/* initialize by an array with array-length */ |
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/* init_key is the array for initializing keys */ |
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/* key_length is its length */ |
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/* slight change for C++, 2004/2/26 */ |
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MersenneTwister.prototype.init_by_array = function(init_key, key_length) { |
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var i, j, k; |
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this.init_genrand(19650218); |
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i=1; j=0; |
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k = (this.N>key_length ? this.N : key_length); |
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for (; k; k--) { |
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var s = this.mt[i-1] ^ (this.mt[i-1] >>> 30) |
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this.mt[i] = (this.mt[i] ^ (((((s & 0xffff0000) >>> 16) * 1664525) << 16) + ((s & 0x0000ffff) * 1664525))) |
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+ init_key[j] + j; /* non linear */ |
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this.mt[i] >>>= 0; /* for WORDSIZE > 32 machines */ |
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i++; j++; |
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if (i>=this.N) { this.mt[0] = this.mt[this.N-1]; i=1; } |
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if (j>=key_length) j=0; |
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} |
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for (k=this.N-1; k; k--) { |
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var s = this.mt[i-1] ^ (this.mt[i-1] >>> 30); |
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this.mt[i] = (this.mt[i] ^ (((((s & 0xffff0000) >>> 16) * 1566083941) << 16) + (s & 0x0000ffff) * 1566083941)) |
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- i; /* non linear */ |
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this.mt[i] >>>= 0; /* for WORDSIZE > 32 machines */ |
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i++; |
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if (i>=this.N) { this.mt[0] = this.mt[this.N-1]; i=1; } |
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} |
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this.mt[0] = 0x80000000; /* MSB is 1; assuring non-zero initial array */ |
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} |
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/* generates a random number on [0,0xffffffff]-interval */ |
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MersenneTwister.prototype.genrand_int32 = function() { |
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var y; |
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var mag01 = new Array(0x0, this.MATRIX_A); |
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/* mag01[x] = x * MATRIX_A for x=0,1 */ |
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if (this.mti >= this.N) { /* generate N words at one time */ |
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var kk; |
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if (this.mti == this.N+1) /* if init_genrand() has not been called, */ |
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this.init_genrand(5489); /* a default initial seed is used */ |
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for (kk=0;kk<this.N-this.M;kk++) { |
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y = (this.mt[kk]&this.UPPER_MASK)|(this.mt[kk+1]&this.LOWER_MASK); |
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this.mt[kk] = this.mt[kk+this.M] ^ (y >>> 1) ^ mag01[y & 0x1]; |
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} |
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for (;kk<this.N-1;kk++) { |
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y = (this.mt[kk]&this.UPPER_MASK)|(this.mt[kk+1]&this.LOWER_MASK); |
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this.mt[kk] = this.mt[kk+(this.M-this.N)] ^ (y >>> 1) ^ mag01[y & 0x1]; |
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} |
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y = (this.mt[this.N-1]&this.UPPER_MASK)|(this.mt[0]&this.LOWER_MASK); |
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this.mt[this.N-1] = this.mt[this.M-1] ^ (y >>> 1) ^ mag01[y & 0x1]; |
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this.mti = 0; |
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} |
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y = this.mt[this.mti++]; |
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/* Tempering */ |
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y ^= (y >>> 11); |
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y ^= (y << 7) & 0x9d2c5680; |
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y ^= (y << 15) & 0xefc60000; |
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y ^= (y >>> 18); |
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return y >>> 0; |
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} |
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/* generates a random number on [0,0x7fffffff]-interval */ |
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MersenneTwister.prototype.genrand_int31 = function() { |
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return (this.genrand_int32()>>>1); |
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} |
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/* generates a random number on [0,1]-real-interval */ |
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MersenneTwister.prototype.genrand_real1 = function() { |
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return this.genrand_int32()*(1.0/4294967295.0); |
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/* divided by 2^32-1 */ |
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} |
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/* generates a random number on [0,1)-real-interval */ |
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MersenneTwister.prototype.random = function() { |
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return this.genrand_int32()*(1.0/4294967296.0); |
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/* divided by 2^32 */ |
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} |
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/* generates a random number on (0,1)-real-interval */ |
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MersenneTwister.prototype.genrand_real3 = function() { |
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return (this.genrand_int32() + 0.5)*(1.0/4294967296.0); |
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/* divided by 2^32 */ |
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} |
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/* generates a random number on [0,1) with 53-bit resolution*/ |
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MersenneTwister.prototype.genrand_res53 = function() { |
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var a=this.genrand_int32()>>>5, b=this.genrand_int32()>>>6; |
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return(a*67108864.0+b)*(1.0/9007199254740992.0); |
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} |
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/* These real versions are due to Isaku Wada, 2002/01/09 added */ |
banksean revised this gist