1 ! Copyright (C) 2005, 2008 Doug Coleman.
2 ! See http://factorcode.org/license.txt for BSD license.
3 ! mersenne twister based on
4 ! http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c
5 USING: kernel math namespaces sequences sequences.private system
6 init accessors math.ranges random math.bitwise combinators
7 specialized-arrays.uint fry ;
8 IN: random.mersenne-twister
12 TUPLE: mersenne-twister { seq uint-array } { i fixnum } ;
16 : mt-a HEX: 9908b0df ; inline
18 : wrap-nth ( n seq -- obj )
19 [ length mod ] keep nth-unsafe ; inline
21 : set-wrap-nth ( obj n seq -- )
22 [ length mod ] keep set-nth-unsafe ; inline
24 : calculate-y ( n seq -- y )
25 [ wrap-nth 31 mask-bit ]
26 [ [ 1+ ] [ wrap-nth ] bi* 31 bits ] 2bi bitor ; inline
28 : (mt-generate) ( n seq -- next-mt )
31 [ 2/ ] [ odd? mt-a 0 ? ] bi bitxor
33 [ mt-m + ] [ wrap-nth ] bi*
36 : mt-generate ( mt -- )
39 _ [ (mt-generate) ] [ set-wrap-nth ] 2bi
41 ] [ 0 >>i drop ] bi ; inline
43 : init-mt-formula ( i seq -- f(seq[i]) )
44 dupd wrap-nth dup -30 shift bitxor 1812433253 * + 1+ 32 bits ; inline
46 : init-mt-rest ( seq -- )
48 _ [ init-mt-formula ] [ [ 1+ ] dip set-wrap-nth ] 2bi
51 : init-mt-seq ( seed -- seq )
52 32 bits mt-n <uint-array>
53 [ set-first ] [ init-mt-rest ] [ ] tri ;
55 : mt-temper ( y -- yt )
57 dup 7 shift HEX: 9d2c5680 bitand bitxor
58 dup 15 shift HEX: efc60000 bitand bitxor
59 dup -18 shift bitxor ; inline
61 : next-index ( mt -- i )
62 dup i>> dup mt-n < [ nip ] [ drop mt-generate 0 ] if ; inline
66 : <mersenne-twister> ( seed -- obj )
67 init-mt-seq 0 mersenne-twister boa
70 M: mersenne-twister seed-random ( mt seed -- )
71 init-mt-seq >>seq drop ;
73 M: mersenne-twister random-32* ( mt -- r )
75 [ seq>> wrap-nth mt-temper ]
76 [ [ 1+ ] change-i drop ] tri ;
81 [ 32 random-bits ] with-system-random
82 <mersenne-twister> random-generator set-global
83 ] "bootstrap.random" add-init-hook