uxn/projects/examples/demos/prng.tal

83 lines
1.9 KiB
Tal

( pseudo-random number generator,
based on two 16-bit xorshift algorithms by George Marsaglia
http://www.jstatsoft.org/v08/i14/paper )
( devices )
|00 @System [ &vector $2 &wst $1 &rst $1 &pad $4 &r $2 &g $2 &b $2 &debug $1 &halt $1 ]
|20 @Screen [ &vector $2 &width $2 &height $2 &pad $2 &x $2 &y $2 &addr $2 &pixel $1 &sprite $1 ]
|b0 @DateTime [ &year $2 &month $1 &day $1 &hour $1 &minute $1 &second $1 &dotw $1 &doty $2 &isdst $1 ]
( variables )
|0000
( program )
|0100 ( -> )
( init )
;on-frame .Screen/vector DEO2
( seed prng (must be nonzero) )
#00 .DateTime/second DEI
#00 .DateTime/minute DEI #60 SFT2 EOR2
#00 .DateTime/hour DEI #c0 SFT2 EOR2 ;prng2/x STA2
#00 .DateTime/hour DEI #04 SFT2
#00 .DateTime/day DEI #10 SFT2 EOR2
#00 .DateTime/month DEI #60 SFT2 EOR2
#00 .DateTime/year DEI #a0 SFT2 EOR2 ;prng2/y STA2
;prng2/x LDA2 ;prng2/y LDA2 EOR2
ORAk ,&non-zero JCN INC2 &non-zero
;prng/seed STA2
( theme )
#0fe5 .System/r DEO2
#0fc5 .System/g DEO2
#0f25 .System/b DEO2
BRK
@on-frame ( -> )
#c0
&loop
,draw-pixel JSR
INC
DUP ,&loop JCN
POP
BRK
@draw-pixel
,prng2 JSR
#00 SWP .Screen/x DEO2
#00 SWP .Screen/y DEO2
#01 .Screen/pixel DEO
JMP2r
@prng ( -- number* )
( returns the next number in a 65,535-long sequence,
which is never zero but every other 16-bit number
appears once before the sequence repeats )
( http://www.retroprogramming.com/2017/07/ xorshift-pseudorandom-numbers-in-z80.html )
,&seed LDR2
DUP2 #70 SFT2 EOR2
DUP2 #09 SFT2 EOR2
DUP2 #80 SFT2 EOR2
,&seed STR2k POP
JMP2r
&seed $2
@prng2 ( -- number* )
( returns the next number in a (2^32-1)-long sequence )
( http://b2d-f9r.blogspot.com/2010/08/ 16-bit-xorshift-rng-now-with-more.html )
,&x LDR2
DUP2 #50 SFT2 EOR2
DUP2 #03 SFT2 EOR2
,&y LDR2 DUP2 ,&x STR2
DUP2 #01 SFT2 EOR2 EOR2
,&y STR2k POP
JMP2r
&x $2
&y $2