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: alien.c-types alien.data kernel math namespaces sequences
6 sequences.private system init accessors math.ranges random
7 math.bitwise combinators specialized-arrays fry ;
8 SPECIALIZED-ARRAY: uint
9 IN: random.mersenne-twister
13 TUPLE: mersenne-twister { seq uint-array } { i fixnum } ;
17 CONSTANT: a uint-array{ 0 0x9908b0df }
20 [ nth-unsafe 31 mask-bit ]
21 [ [ 1 + ] [ nth-unsafe ] bi* 31 bits ] 2bi bitor ; inline
23 : mt[k] ( offset n seq -- )
25 [ [ + ] dip nth-unsafe ]
26 [ y [ 2/ ] [ 1 bitand a nth ] bi bitxor ] 2bi
28 ] 2keep set-nth-unsafe ; inline
30 : mt-generate ( mt -- )
33 [ [ n m - ] dip '[ [ m ] dip _ mt[k] ] each-integer ]
34 [ [ m 1 - ] dip '[ [ m n - ] [ n m - + ] bi* _ mt[k] ] each-integer ]
36 ] [ 0 >>i drop ] bi ; inline
38 : init-mt-formula ( i seq -- f(seq[i]) )
39 dupd nth dup -30 shift bitxor 1812433253 * + 1 + 32 bits ; inline
41 : init-mt-rest ( seq -- )
43 _ [ init-mt-formula ] [ [ 1 + ] dip set-nth ] 2bi
44 ] each-integer ; inline
46 : init-mt-seq ( seed -- seq )
47 32 bits n uint <c-array>
48 [ set-first ] [ init-mt-rest ] [ ] tri ; inline
50 : mt-temper ( y -- yt )
52 dup 7 shift 0x9d2c5680 bitand bitxor
53 dup 15 shift 0xefc60000 bitand bitxor
54 dup -18 shift bitxor ; inline
56 : next-index ( mt -- i )
57 dup i>> dup n < [ nip ] [ drop mt-generate 0 ] if ; inline
61 : <mersenne-twister> ( seed -- obj )
62 init-mt-seq 0 mersenne-twister boa
65 M: mersenne-twister seed-random ( mt seed -- mt' )
71 M: mersenne-twister random-32* ( mt -- r )
73 [ seq>> nth-unsafe mt-temper ]
74 [ [ 1 + ] change-i drop ] tri ;
76 : default-mersenne-twister ( -- mersenne-twister )
77 [ 32 random-bits ] with-system-random
81 default-mersenne-twister random-generator set-global
82 ] "bootstrap.random" add-startup-hook