71 lines
1.8 KiB
Factor
Executable File
71 lines
1.8 KiB
Factor
Executable File
! Copyright (C) 2005, 2008 Doug Coleman.
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! See http://factorcode.org/license.txt for BSD license.
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! mersenne twister based on
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! http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c
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USING: arrays kernel math namespaces sequences system init
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accessors math.ranges random circular math.bitfields.lib
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combinators ;
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IN: random.mersenne-twister
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<PRIVATE
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TUPLE: mersenne-twister seq i ;
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: mt-n 624 ; inline
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: mt-m 397 ; inline
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: mt-a HEX: 9908b0df ; inline
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: calculate-y ( n seq -- y )
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[ nth 32 mask-bit ]
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[ [ 1+ ] [ nth ] bi* 31 bits ] 2bi bitor ; inline
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: (mt-generate) ( n seq -- next-mt )
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[
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calculate-y
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[ 2/ ] [ odd? mt-a 0 ? ] bi bitxor
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] [
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[ mt-m + ] [ nth ] bi*
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] 2bi bitxor ;
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: mt-generate ( mt -- )
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[
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mt-n swap seq>> [
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[ (mt-generate) ] [ set-nth ] 2bi
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] curry each
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] [ 0 >>i drop ] bi ;
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: init-mt-formula ( i seq -- f(seq[i]) )
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dupd nth dup -30 shift bitxor 1812433253 * + 1+ 32 bits ;
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: init-mt-rest ( seq -- )
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mt-n 1- swap [
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[ init-mt-formula ] [ >r 1+ r> set-nth ] 2bi
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] curry each ;
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: init-mt-seq ( seed -- seq )
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32 bits mt-n 0 <array> <circular>
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[ set-first ] [ init-mt-rest ] [ ] tri ;
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: mt-temper ( y -- yt )
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dup -11 shift bitxor
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dup 7 shift HEX: 9d2c5680 bitand bitxor
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dup 15 shift HEX: efc60000 bitand bitxor
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dup -18 shift bitxor ; inline
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: next-index ( mt -- i )
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dup i>> dup mt-n < [ nip ] [ drop mt-generate 0 ] if ;
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PRIVATE>
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: <mersenne-twister> ( seed -- obj )
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init-mt-seq 0 mersenne-twister boa
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dup mt-generate ;
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M: mersenne-twister seed-random ( mt seed -- )
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init-mt-seq >>seq drop ;
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M: mersenne-twister random-32* ( mt -- r )
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[ next-index ]
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[ seq>> nth mt-temper ]
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[ [ 1+ ] change-i drop ] tri ;
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