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random-coloring.scm
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random-coloring.scm
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#!/usr/bin/env chicken-scheme
;; [[file:~/prg/scm/aima/aima.org::*6.10][6\.10:1]]
(use ;; aima-tessellation
aima-csp
call-with-environment-variables
debug
define-record-and-printer
files
format
graphviz
matchable
random-bsd
shell
srfi-1
srfi-95)
(define (random-element list)
(list-ref list (random (length list))))
(define (solution? assignment csp)
(call/cc
(lambda (return)
(hash-table-walk (csp-neighbors csp)
(lambda (whence whithers)
(for-each
(lambda (whither)
(let ((constraint (hash-table-ref (csp-constraints csp) (cons whence whither))))
(unless (constraint (hash-table-ref assignment whence)
(hash-table-ref assignment whither))
(return #f))))
whithers)))
(return #t))))
(define (conflicted-variables assignment csp)
(hash-table-fold
(csp-constraints csp)
(lambda (scope constraint conflicts)
(let ((x (car scope))
(y (cdr scope)))
(if (constraint (hash-table-ref assignment x)
(hash-table-ref assignment y))
conflicts
(lset-adjoin eq? conflicts x y))))
'()))
(define max-steps (make-parameter 10000))
(define (min-conflicts csp)
(let ((assignment (hash-table-fold
(csp-domains csp)
(lambda (variable domain assignment)
(hash-table-set! assignment variable (random-element domain))
assignment)
(make-hash-table))))
(let iter ((variables (conflicted-variables assignment csp))
(step (max-steps)))
(cond ((null? variables) assignment)
((zero? step) failure)
(else
(let ((conflicted-variable (random-element variables)))
(let ((neighbor-constraints
(map (lambda (neighbor)
(cons neighbor
(hash-table-ref
(csp-constraints csp)
(cons conflicted-variable neighbor))))
(hash-table-ref (csp-neighbors csp) conflicted-variable)))
(domain (hash-table-ref (csp-domains csp) conflicted-variable)))
(let* ((value-conflicts
(sort
(map (lambda (value)
(cons value
(count (complement values)
(map (match-lambda
((neighbor . constraint)
(constraint
value
(hash-table-ref
assignment
neighbor))))
neighbor-constraints))))
domain)
<
cdr))
(min-conflict
(cdar value-conflicts))
(min-conflicts
(take-while (lambda (conflict) (= (cdr conflict) min-conflict)) value-conflicts))
(min-conflicting-value
(car (random-element min-conflicts))))
;; (debug (hash-table->alist assignment)
;; conflicted-variable
;; value-conflicts
;; min-conflicts
;; min-conflicting-value)
(hash-table-set! assignment conflicted-variable min-conflicting-value)
(iter (conflicted-variables assignment csp) (sub1 step))))))))))
(define-syntax time+value
(ir-macro-transformer
(lambda (expression inject compare)
`(begin (##sys#start-timer)
(let ((value ,@(cdr expression)))
(values (vector-ref (##sys#stop-timer) 0) value))))))
(define (experiment name solution)
(let iter ((n 2))
(let ((map (random-map n))
(domains (make-hash-table))
(constraints (make-hash-table)))
(set-domains! domains (hash-table-keys map) '(red green blue yellow))
(hash-table-walk map
(lambda (whence whithers)
(for-each (lambda (whither)
(set-bidirectional-constraint!
constraints
whence
whither
neq?
neq?))
whithers)))
(let ((csp (make-csp domains constraints map)))
(call-with-values (lambda () (time+value (solution csp)))
(lambda (time value)
(unless (failure? value)
(let ((file (call-with-environment-variables
'(("TMPDIR" . "random-coloring"))
(lambda () (create-temporary-file)))))
(with-output-to-file file
(lambda () (format #t "~a,~a,~a~%" name n time)))))
(debug name n time value)))))
(iter (add1 n))))
;; (experiment "min-conflicts"
;; (parameterize ((max-steps 10000000))
;; min-conflicts))
;; (experiment "backtracking"
;; (parameterize ((inference (lambda x (make-hash-table))))
;; backtracking-search))
;; (experiment "forward-checking"
;; backtracking-search)
(let ((map (random-map 10))
(domains (make-hash-table))
(constraints (make-hash-table)))
(set-domains! domains (hash-table-keys map) '(red green blue yellow))
(hash-table-walk map
(lambda (whence whithers)
(for-each (lambda (whither)
(set-bidirectional-constraint!
constraints
whence
whither
neq?
neq?))
whithers)))
(let ((csp (make-csp domains constraints map)))
(let ((solution (parameterize ((max-steps 10000)) (min-conflicts csp))
;; (backtracking-search csp)
;; (parameterize ((inference (lambda x (make-hash-table))))
;; (backtracking-search csp))
))
(unless (failure? solution)
(display-map-as-png map solution)
(debug (hash-table->alist solution))))))
;; 6\.10:1 ends here