random.fs

\ generates random numbers                             12jan94py

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0 [IF] \ pretty pad linear congruent generator
    Variable seed
    
    $10450405 Constant generator
    
    : rnd  ( -- n )  seed @ generator um* drop 1+ dup seed ! ;
    : seed-init ( -- )  ntime drop seed +!  rnd drop ;
[ELSE]
    \ hash based generator, deterministic
    \ seed-init feeds entropy into the generator
    \ 2.2 times slower than lcg on 64 bit platform
    \ passed SmallCrush, Rabbit, Alphabit, FIPS-140-2
    $10 buffer: rng-state
    8 buffer: seed

    : rnd ( -- n ) seed 7 0 rng-state hashkey2 rng-state 2@ xor ;
    cell 8 = [IF]
	: seed-init ( -- ) ntime drop seed ! rnd drop ;
    [ELSE]
	: seed-init ( -- ) ntime seed 2! rnd drop ;
    [THEN]
[THEN]
seed-init

: random ( n -- 0..n-1 )  rnd um* nip ;