A Decomposition Based Heuristic
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The solution of the DSP could be considerably simplified if some “important” disjunctive edges were oriented the right way in advance. Pesch and Tetzlaff [PT96], for instance, showed that regarding the famous instance FT10 of the JSP, one single “difficult” edge orientation exists which for the most part contributes to its intractability. Orienting this edge in the right direction, the optimal solution is found and verified in a fraction of the original time. Unfortunately, however, finding important edge orientations which occur in an optimal solution must, by definition, be a difficult task. Indeed, if an edge orientation can be easily found then orienting this edge cannot simplify the solution of the problem a lot, because it can be easily found. This dilemma can only be resolved if accuracy is sacrificed for efficiency, i.e. if we accept that some edge orientations derived may be wrong. The simplest heuristic method is a random selection of some edge orientations, however, the “deduced” edge orientations will seldomly be oriented in the right direction.
KeywordsComputational Result Problem Instance Solution Time Constraint Propagation Large Instance
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