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 : mersenne-wrap ( n -- n' )
19 dup mt-n > [ mt-n - ] when ; inline
21 : wrap-nth ( n seq -- obj )
22 [ mersenne-wrap ] dip nth-unsafe ; inline
24 : set-wrap-nth ( obj n seq -- )
25 [ mersenne-wrap ] dip set-nth-unsafe ; inline
27 : calculate-y ( n seq -- y )
28 [ wrap-nth 31 mask-bit ]
29 [ [ 1+ ] [ wrap-nth ] bi* 31 bits ] 2bi bitor ; inline
31 : (mt-generate) ( n seq -- next-mt )
34 [ 2/ ] [ odd? mt-a 0 ? ] bi bitxor
36 [ mt-m + ] [ wrap-nth ] bi*
39 : mt-generate ( mt -- )
42 _ [ (mt-generate) ] [ set-wrap-nth ] 2bi
44 ] [ 0 >>i drop ] bi ; inline
46 : init-mt-formula ( i seq -- f(seq[i]) )
47 dupd wrap-nth dup -30 shift bitxor 1812433253 * + 1+ 32 bits ; inline
49 : init-mt-rest ( seq -- )
51 _ [ init-mt-formula ] [ [ 1+ ] dip set-wrap-nth ] 2bi
54 : init-mt-seq ( seed -- seq )
55 32 bits mt-n <uint-array>
56 [ set-first ] [ init-mt-rest ] [ ] tri ; inline
58 : mt-temper ( y -- yt )
60 dup 7 shift HEX: 9d2c5680 bitand bitxor
61 dup 15 shift HEX: efc60000 bitand bitxor
62 dup -18 shift bitxor ; inline
64 : next-index ( mt -- i )
65 dup i>> dup mt-n < [ nip ] [ drop mt-generate 0 ] if ; inline
69 : <mersenne-twister> ( seed -- obj )
70 init-mt-seq 0 mersenne-twister boa
73 M: mersenne-twister seed-random ( mt seed -- )
74 init-mt-seq >>seq drop ;
76 M: mersenne-twister random-32* ( mt -- r )
78 [ seq>> wrap-nth mt-temper ]
79 [ [ 1+ ] change-i drop ] tri ;
84 [ 32 random-bits ] with-system-random
85 <mersenne-twister> random-generator set-global
86 ] "bootstrap.random" add-init-hook