Profound Degree: A Conservative Heuristic to Repair Dynamic CSPs

Abstract

Part 4: Hybrid - Changing EnvironmentsInternational audienceFor a better treatment of Dynamic Constraint Satisfaction Problems (DCSPs), several techniques have been developed to be used in repair algorithms. We cite, for example, the variables/values ordering heuristics and local search techniques.We distinguish between static heuristics, which calculate their values once at the beginning of the search, and dynamic heuristics that use an expensive intelligence in terms of solving time.In this paper, we propose a new static variable ordering heuristic, Profound Degree (pdeg), based on deg heuristic, which calculates the degree of influence of a given variable, on the whole constraints network, relatively to its position in the network.We evaluate this heuristic on the Extended Partial-order Dynamic Backtracking (EPBD) approach, which is an approach to repair DCSPs solutions, and we compare it to the best-known variables ordering heuristics (VOHs) for repairing. The evaluation of performance is on random binary problems and meeting scheduling problems, with the criteria of computation time, number of constraints checks and Hamming distance between the former and the current solution

Lazy Repairing Backtracking for Dynamic Constraint Satisfaction Problems

“…The next constraint to check is C 24 which is violated (line 9), ( 5) and ( 6) are tested, then, ( 7) is generated, the value of X4 is changed (line 10) and C 14 , the only constraint in free cstrs concerning X4, is moved to to check list. The next checked constraint is C 23 which is violated (line 11), the tested orders are (5) then (6), and (7). As no order exists between the two variables, the chosen heuristic is used to generate (8), then, the value of X3 is changed (line 12).…”

“…MAC-2001 is combined to the dom/deg heuristic like in [14]. We note that the arc consistency strategy can be also improved by using dom/wdeg [7], but as shown in [15], this heuristic is efficient essentially in combination with AC-3.…”