From fbef580a0190d44b764923a5ea66e673210630c6 Mon Sep 17 00:00:00 2001 From: Sergiu Ivanov Date: Sun, 23 Feb 2020 00:04:19 +0100 Subject: [PATCH] networks: Add get-interaction-sign. --- networks-tests.rkt | 7 ++++++- networks.rkt | 49 +++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 54 insertions(+), 2 deletions(-) diff --git a/networks-tests.rkt b/networks-tests.rkt index 2dc48cd..5a8aa7c 100644 --- a/networks-tests.rkt +++ b/networks-tests.rkt @@ -71,4 +71,9 @@ '(((a . #t) (b . #t)) ((a . #t) (b . #f)) ((a . #f) (b . #t)) - ((a . #f) (b . #f))))) + ((a . #f) (b . #f)))) + + (let ([n #hash((a . (not b)) (b . a))] + [doms (make-immutable-hash (for/list ([var '(a b)]) (cons var '(#f #t))))]) + (check-equal? (get-interaction-sign n doms 'a 'b) '+) + (check-equal? (get-interaction-sign n doms 'b 'a) '-))) diff --git a/networks.rkt b/networks.rkt index 56eb9f1..6b34c5f 100644 --- a/networks.rkt +++ b/networks.rkt @@ -24,7 +24,8 @@ [list-interactions (-> network-form? variable? (listof variable?))] [build-interaction-graph (-> network-form? graph?)] [build-all-states (-> (listof (cons/c variable? generic-set?)) (listof state?))] - [build-all-states-same-domain (-> (listof variable?) generic-set? (listof state?))]) + [build-all-states-same-domain (-> (listof variable?) generic-set? (listof state?))] + [get-interaction-sign (-> network-form? (hash/c variable? generic-set?) variable? variable? (or/c '+ '- '0))]) ;; Predicates (contract-out [variable? (-> any/c boolean?)] [state? (-> any/c boolean?)] @@ -157,3 +158,49 @@ ;;; builds the list of all possible states. (define (build-all-states-same-domain vars domain) (build-all-states (for/list ([v vars]) (cons v domain)))) + +;;; Given two interacting variables of a network form and the domains +;;; of the variables, returns '+ if the interaction is monotonously +;;; increasing, '- if it is monotonously decreasing, and '0 otherwise. +;;; +;;; This function does not check whether the two variables indeed +;;; interact. Its behaviour is undefined if the variables do not +;;; interact. +;;; +;;; /!\ This function iterates through almost all of the states of the +;;; network, so its performance decreases very quickly with network +;;; size. +(define (get-interaction-sign network-form doms x y) + (let* ([dom-x (hash-ref doms x)] + [dom-y (hash-ref doms y)] + [network (network-form->network network-form)] + ;; Replace the domain of x by a dummy singleton. + [doms-no-x (hash-set doms x '(#f))] + ;; Build all the states, but as if x were not there: since I + ;; replace its domain by a singleton, all states will contain + ;; the same value for x. + [states-no-x (build-all-states (hash->list doms-no-x))] + ;; Go through all states, then through all ordered pairs of + ;; values of x, generate pairs of states (s1, s2) such that x + ;; has a smaller value in s1, and check that updating y in s1 + ;; yields a smaller value than updating y in s2. I rely on + ;; the fact that the domains are ordered. + [x-y-interactions (for*/list ([s states-no-x] + [x1 dom-x] ; ordered pairs of values of x + [x2 (cdr (member x1 dom-x))]) + (let* ([s1 (hash-set s x x1)] ; s1(x) < s2(x) + [s2 (hash-set s x x2)] + [y1 ((hash-ref network y) s1)] + [y2 ((hash-ref network y) s2)]) + ;; y1 <= y2? + (<= (index-of dom-y y1) (index-of dom-y y2))))]) + (cond + ;; If, in all interactions, y1 <= y2, then we have an + ;; increasing/promoting interaction between x and y. + [(andmap (λ (x) (eq? x #t)) x-y-interactions) '+] + ;; If, in all interactions, y1 > y2, then we have an + ;; decreasing/inhibiting interaction between x and y. + [(andmap (λ (x) (eq? x #f)) x-y-interactions) '-] + ;; Otherwise the interaction is neither increasing nor + ;; decreasing. + [else '0])))