/
stochastic-constraints.ss
181 lines (159 loc) · 5.3 KB
/
stochastic-constraints.ss
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#!r6rs
(library
(stochastic-constraints)
(export set-stochastic-strategy! create-distribution-variable
distribution-variable-distribution stochastic-solution
assert-stochastic-constraint!)
(import (rnrs) (QobiScheme) (stochastic-scheme))
(define *strategy* #f)
(define-record-type distribution-variable
(fields (mutable distribution) (mutable demons)))
(define (set-stochastic-strategy! strategy) (set! *strategy* strategy))
(define (distribution-variable-distribution-local-set!
distribution-variable distribution)
(let ((distribution
(distribution-variable-distribution distribution-variable)))
(upon-bottom (distribution-variable-distribution-set!
distribution-variable distribution)))
(distribution-variable-distribution-set! distribution-variable distribution))
(define (distribution-variable-demons-local-set! distribution-variable demons)
(let ((demons (distribution-variable-demons distribution-variable)))
(upon-bottom
(distribution-variable-demons-set! distribution-variable demons)))
(distribution-variable-demons-set! distribution-variable demons))
(define (create-distribution-variable distribution)
(let ((distribution (coalesce-duplicates distribution)))
(when (null? distribution) (bottom))
(make-distribution-variable distribution '())))
(define (restrict-distribution! d distribution)
(when (null? distribution) (bottom))
(when (< (length distribution)
(length (distribution-variable-distribution d)))
(distribution-variable-distribution-local-set! d distribution)
(for-each (lambda (demon) (demon)) (distribution-variable-demons d))))
(define (bound? d) (null? (rest (distribution-variable-distribution d))))
(define (binding d) (car (first (distribution-variable-distribution d))))
(define (stochastic-solution ds)
(let loop ((ds ds) (xs '()))
(if (null? ds)
(reverse xs)
(let ((pair
(draw-pair (distribution-variable-distribution (first ds)))))
(restrict-distribution! (first ds) (list pair))
(loop (rest ds) (cons (first pair) xs))))))
(define (some-element predicate d)
(some (lambda (pair) (predicate (car pair)))
(distribution-variable-distribution d)))
(define (one-element predicate d)
(one (lambda (pair) (predicate (car pair)))
(distribution-variable-distribution d)))
(define (the-element predicate d)
(list (find-if (lambda (pair) (predicate (car pair)))
(distribution-variable-distribution d))))
(define (the-elements predicate d)
(remove-if-not (lambda (pair) (predicate (car pair)))
(distribution-variable-distribution d)))
(define (attach-demon! demon d)
(distribution-variable-demons-local-set!
d (cons demon (distribution-variable-demons d)))
(demon))
(define (assert-constraint-efd! constraint ds)
(for-each
(lambda (d)
(attach-demon! (lambda ()
(when (every bound? ds)
(unless (apply constraint (map binding ds)) (bottom))))
d))
ds))
(define (assert-constraint-fc! constraint ds)
(for-each
(lambda (d)
(attach-demon!
(lambda ()
(when (one (lambda (d) (not (bound? d))) ds)
(let* ((i (position-if (lambda (d) (not (bound? d))) ds))
(d (list-ref ds i)))
(unless (some-element
(lambda (x)
(apply
constraint
(map-indexed (lambda (d j) (if (= j i) x (binding d))) ds)))
d)
(bottom)))))
d))
ds))
(define (assert-constraint-vp! constraint ds)
(for-each
(lambda (d)
(attach-demon!
(lambda ()
(when (one (lambda (d) (not (bound? d))) ds)
(let* ((i (position-if (lambda (d) (not (bound? d))) ds))
(d (list-ref ds i)))
(when (one-element
(lambda (x)
(apply
constraint
(map-indexed (lambda (d j) (if (= j i) x (binding d))) ds)))
d)
(restrict-distribution!
d
(the-element
(lambda (x)
(apply constraint
(map-indexed (lambda (d j) (if (= j i) x (binding d))) ds)))
d))))))
d))
ds))
(define (assert-constraint-gfc! constraint ds)
(for-each
(lambda (d)
(attach-demon!
(lambda ()
(when (one (lambda (d) (not (bound? d))) ds)
(let* ((i (position-if (lambda (d) (not (bound? d))) ds))
(d (list-ref ds i)))
(restrict-distribution!
d
(the-elements
(lambda (x)
(apply constraint
(map-indexed (lambda (d j) (if (= j i) x (binding d))) ds)))
d)))))
d))
ds))
(define (assert-constraint-ac! constraint ds)
(for-each
(lambda (d)
(attach-demon!
(lambda ()
(for-each-indexed
(lambda (d i)
(restrict-distribution!
d
(the-elements
(lambda (x)
(let loop ((ds ds) (xs '()) (j 0))
(if (null? ds)
(apply constraint (reverse xs))
(if (= j i)
(loop (rest ds) (cons x xs) (+ j 1))
(some-element
(lambda (pair) (loop (rest ds) (cons (car pair) xs) (+ j 1)))
(first ds))))))
d)))
ds))
d))
ds))
(define (assert-stochastic-constraint! constraint . ds)
(case *strategy*
((efd) (assert-constraint-efd! constraint ds))
((fc) (assert-constraint-efd! constraint ds)
(assert-constraint-fc! constraint ds))
((vp) (assert-constraint-efd! constraint ds)
(assert-constraint-fc! constraint ds)
(assert-constraint-vp! constraint ds))
((gfc) (assert-constraint-efd! constraint ds)
(assert-constraint-gfc! constraint ds))
((ac) (assert-constraint-ac! constraint ds))
(else (error #f "Unrecognized strategy")))))