; george marsaglia's random number generators
(define (ipow b e)
(cond ((zero? e) 1)
((even? e) (ipow (* b b) (/ e 2)))
(else (* b (ipow (* b b) (/ (- e 1) 2))))))
(define (logand a b)
(if (or (zero? a) (zero? b)) 0
(+ (* (logand (floor (/ a 2)) (floor (/ b 2))) 2)
(if (or (even? a) (even? b)) 0 1))))
(define (logxor a b)
(cond ((zero? a) b)
((zero? b) a)
(else
(+ (* (logxor (floor (/ a 2)) (floor (/ b 2))) 2)
(if (even? a)
(if (even? b) 0 1)
(if (even? b) 1 0))))))
(define (ash int cnt)
(if (negative? cnt)
(let ((n (ipow 2 (- cnt))))
(if (negative? int)
(+ -1 (quotient (+ 1 int) n))
(quotient int n)))
(* (ipow 2 cnt) int)))
(define mwc #f)
(define shr3 #f)
(define cong #f)
(define fib #f)
(define kiss #f)
(define lfib4 #f)
(define swb #f)
(define uni #f)
(define vni #f)
(define settable #f)
(let ((z 362436069) (w 521288629) (jsr 123456789)
(jcong 380116160) (a 224466889) (b 7584631)
(t (make-vector 256 0)) (x 0) (y 0) (c 0))
(define (mod8 n) (modulo n 256))
(define (mod32 n) (modulo n 4294967296))
(define (ref i) (vector-ref t (mod8 i)))
(set! mwc (lambda ()
(set! z (mod32 (+ (* 36969 (logand z 65535)) (ash z -16))))
(set! w (mod32 (+ (* 18000 (logand w 65535)) (ash w -16))))
(mod32 (+ (ash z 16) w))))
(set! shr3 (lambda ()
(set! jsr (mod32 (logxor jsr (ash jsr 17))))
(set! jsr (mod32 (logxor jsr (ash jsr -13))))
(set! jsr (mod32 (logxor jsr (ash jsr 5)))) jsr))
(set! cong (lambda ()
(set! jcong (mod32 (+ (* 69069 jcong) 1234567))) jcong))
(set! fib (lambda ()
(set! b (mod32 (+ a b))) (set! a (mod32 (- b a))) a))
(set! kiss (lambda ()
(mod32 (+ (logxor (mwc) (cong)) (shr3)))))
(set! lfib4 (lambda ()
(set! c (mod8 (+ c 1)))
(vector-set! t c (mod32 (+ (ref c) (ref (+ c 58))
(ref (+ c 119)) (ref (+ c 178))))) (ref c)))
(set! swb (lambda ()
(set! c (mod8 (+ c 1)))
(let ((bro (if (< x y) 1 0)))
(set! x (mod32 (ref (+ c 34))))
(set! y (mod32 (+ (ref (+ c 19)) bro)))
(vector-set! t c (mod32 (- x y)))
(vector-ref t c))))
(set! uni (lambda ()
(* (kiss) 2.328306e-10)))
(set! vni (lambda ()
(* (- (kiss) 2147483648) 4.6566133-10)))
(set! settable (lambda (i1 i2 i3 i4 i5 i6)
(set! z i1) (set! w i2) (set! jsr i3) (set! jcong i4)
(set! a i5) (set! b i6) (set! x 0) (set! y 0) (set! c 0)
(do ((i 0 (+ i 1))) ((= i 256))
(vector-set! t i (kiss))))))
(define-syntax assert
(syntax-rules ()
((assert expr result)
(if (not (equal? expr result))
(for-each display `(
#\newline "failed assertion:" #\newline
expr #\newline "expected: " ,result
#\newline "returned: " ,expr #\newline))))))
(define (test-rng)
(let ((k 0))
(settable 12345 65435 34221 12345 9983651 95746118)
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 1064612766)) (set! k (lfib4)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 627749721)) (set! k (swb)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 1372460312)) (set! k (kiss)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 1529210297)) (set! k (cong)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 2642725982)) (set! k (shr3)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 904977562)) (set! k (mwc)))
(do ((i 0 (+ i 1))) ((= i 1e6) (assert k 3519793928)) (set! k (fib)))))
(test-rng)