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more cleanup of mersenne-twister -- you can actually understand it now :)

db4
erg 2008-04-03 13:04:24 -05:00
parent d642347f34
commit 5c2b2b024e
1 changed files with 29 additions and 26 deletions
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55
extra/random/mersenne-twister/mersenne-twister.factor
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@ -2,9 +2,9 @@
! See http://factorcode.org/license.txt for BSD license. ! See http://factorcode.org/license.txt for BSD license.
! mersenne twister based on ! mersenne twister based on
! http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c ! http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/CODES/mt19937ar.c
USING: arrays kernel math namespaces sequences system init USING: arrays kernel math namespaces sequences system init
accessors math.ranges random circular math.bitfields.lib ; accessors math.ranges random circular math.bitfields.lib
combinators ;
IN: random.mersenne-twister IN: random.mersenne-twister
<PRIVATE <PRIVATE
@ -14,36 +14,37 @@ TUPLE: mersenne-twister seq i ;
: mt-n 624 ; inline : mt-n 624 ; inline
: mt-m 397 ; inline : mt-m 397 ; inline
: mt-a HEX: 9908b0df ; inline : mt-a HEX: 9908b0df ; inline
: mt-hi HEX: 80000000 bitand ; inline
: mt-lo HEX: 7fffffff bitand ; inline
: set-generated ( y from-elt to seq -- )
>r >r >r [ 2/ ] [ odd? mt-a 0 ? ] bi
r> bitxor bitxor r> r> set-nth ; inline
: calculate-y ( y1 y2 mt -- y ) : calculate-y ( y1 y2 mt -- y )
tuck [ nth mt-hi ] [ nth mt-lo ] 2bi* bitor ; inline tuck
[ nth 32 mask-bit ]
[ nth 31 bits ] 2bi* bitor ; inline
: (mt-generate) ( n mt-seq -- y to from-elt ) : (mt-generate) ( n mt-seq -- next-mt )
[ >r dup 1+ r> calculate-y ] [
[ >r mt-m + r> nth ] [ dup 1+ ] [ calculate-y ] bi*
[ drop ] 2tri ; [ 2/ ] [ odd? mt-a 0 ? ] bi bitxor
] [
[ mt-m + ] [ nth ] bi*
] 2bi bitxor ;
: mt-generate ( mt -- ) : mt-generate ( mt -- )
[ >r mt-n r> seq>> [ [ (mt-generate) ] keep set-generated ] curry each ] [
[ 0 >>i drop ] bi ; mt-n swap seq>> [
[ (mt-generate) ] [ set-nth ] 2bi
] curry each
] [ 0 >>i drop ] bi ;
: init-mt-formula ( seq i -- f(seq[i]) ) : init-mt-formula ( i seq -- f(seq[i]) )
tuck swap nth dup -30 shift bitxor 1812433253 * + dupd nth dup -30 shift bitxor 1812433253 * + 1+ 32 bits ;
1+ 32-bit ;
: init-mt-rest ( seq -- ) : init-mt-rest ( seq -- )
mt-n 1- [ mt-n 1- swap [
dupd [ init-mt-formula ] keep 1+ rot set-nth [ init-mt-formula ] [ >r 1+ r> set-nth ] 2bi
] with each ; ] curry each ;
: init-mt-seq ( seed -- seq ) : init-mt-seq ( seed -- seq )
32-bit mt-n 0 <array> <circular> 32 bits mt-n 0 <array> <circular>
[ set-first ] [ init-mt-rest ] [ ] tri ; [ set-first ] [ init-mt-rest ] [ ] tri ;
: mt-temper ( y -- yt ) : mt-temper ( y -- yt )
@ -52,6 +53,9 @@ TUPLE: mersenne-twister seq i ;
dup 15 shift HEX: efc60000 bitand bitxor dup 15 shift HEX: efc60000 bitand bitxor
dup -18 shift bitxor ; inline dup -18 shift bitxor ; inline
: next-index ( mt -- i )
dup i>> dup mt-n < [ nip ] [ drop mt-generate 0 ] if ;
PRIVATE> PRIVATE>
: <mersenne-twister> ( seed -- obj ) : <mersenne-twister> ( seed -- obj )
@ -62,7 +66,6 @@ M: mersenne-twister seed-random ( mt seed -- )
init-mt-seq >>seq drop ; init-mt-seq >>seq drop ;
M: mersenne-twister random-32* ( mt -- r ) M: mersenne-twister random-32* ( mt -- r )
dup [ i>> ] [ seq>> ] bi [ next-index ]
over mt-n < [ nip >r dup mt-generate 0 r> ] unless [ seq>> nth mt-temper ]
nth mt-temper [ [ 1+ ] change-i drop ] tri ;
swap [ 1+ ] change-i drop ;