B. Smith. Succeed-rst or fail-rst: a case study in variable and value ordering. In Proceedings ILOG Solver and ILOG Scheduler International Users' Conference, Paris, France, 1996.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....(C; O; p; q; r) as the search of a minimal cost sequence composed of the cars to be produced. 2. 2 Utilization Rate The diculty of an instance depends on the number of cars to be produced and the number of di erent options con gurations, but also on the utilization rate of the di erent options [10]. The utilization rate of an option o i corresponds to the ratio of the number of cars requiring o i with respect to the maximum number of cars in a sequence which could have o i while satisfying its capacity constraint, i.e. utilRate(o i ) r(C;o i ) q(o i ) jCj p(o i ) An utilization rate ....

....newViolations function usually contains more than one car so that we may use another heuristic to break further ties. We consider di erent heuristics: 1. Random choice (Rand) choose randomly a car within the set of candidates. 2. Static Highest Utilization Rates (SHU) the idea, introduced in [10], is to choose rst the cars that require the option with highest utilization rate, and to break ties by choosing cars that require the option with second highest utilization rate, and so on. More formally, we choose the car that maximizes the heuristic function SHU (c j ) r(c j ; o i ) ....

B. Smith. Succeed- rst or fail- rst: A case study in variable and value ordering heuristics. In Third Conference on the Practical Applications of Constraint Technology, 321 - 330, 1996

....problem. B.1 Selection of a variable When constructing an assignment, the order in which the variables are assigned is rather important, as the satisfaction of a constraint can only be checked once all its variables have been assigned. Variable ordering heuristics have been studied widely [31] [27]. Some commonly used variable orderings are: most constraining rst ordering, which selects an unassigned variable that is connected (by a constraint) to the largest number of unassigned variables; most constrained rst ordering, which selects an unassigned variable that is connected (by a ....

....is more dicult to anticipate the consequences of the choice of a value on the further assignments of the remaining unassigned variables. Hence, there are very few heuristics for guiding this choice and these heuristics usually are problem dependent, so they cannot be applied to general CSPs (e.g. [27] for the car sequencing problem) The main contribution of ACO for solving CSPs is to provide a general heuristic for choosing values: this choice is made randomly with a probability that depends on a pheromone factor (to evaluate the learnt desirability of the value) and a heuristic factor (to ....

B. Smith. Succeed- rst or fail- rst: A case study in variable and value ordering heuristics. In Third Conference on the Practical Applications of Constraint Technology PACT'97, http://www.scs.leeds.ac.uk/bms/papers.html, pages 321-330, 1997.

....B.1 Selection of a variable When constructing an assignment, the order in which the variables are assigned is rather important as the satisfaction of a constraint can only be checked once all its variables have been assigned. Variable ordering heuristics have been widely studied [3] 10] [20]. Some commonly used variable orderings are the most constraining rst ordering, which selects an unassigned variable that is connected (by a constraint) to the largest number of unassigned variables, the most constrained rst ordering, which selects an unassigned variable that is connected ....

....the consequences of the choice of a value for the current variable on the further assignments of the remaining unassigned variables. Hence, there are very few heuristics for guiding this choice and these heuristics usually are problem dependent so that they cannot be applied to general CSPs (e.g. [20], 21] for the car sequencing problem) The main contribution of Ant Solver is to propose a general heuristic for choosing values, based on the ACO meta heuristic. More precisely, the choice of a value for a variable is made in a stochastic way with respect to a transition probability which ....

B. Smith, \Succeed-rst or fail-rst: A case study in variable and value ordering heuristics," in third Conference on the Practical Applications of Constraint Technology PACT'97, 1996, pp. 321{ 330.

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B. Smith. Succeed-rst or fail-rst: a case study in variable and value ordering. In Proceedings ILOG Solver and ILOG Scheduler International Users' Conference, Paris, France, 1996.

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