Jan Karel Lenstra

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We consider the following scheduling problem. There are m parallel machines and n independent jobs. Each job is to be assigned to one of the machines. The processing of job j on machine i requires time pij. The objective is to find a schedule that minimizes the makespan. Our main result is a polynomial algorithm which constructs a schedule that is(More)
item in the big bin and obtains a profit of 1 while OPT = 2. This also shows that ordering bins in non-increasing capacities does not help improve the performance of Greedy. 5 Conclusions An interesting aspect of our guessing strategy is that it is completely independent of the number of bins and their capacities. This might prove to be useful in other(More)
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We survey solution methods for the job shop scheduling problem with an emphasis on local search. Both deterministic and randomized local search methods as well as the proposed neighborhoods are discussed. We compare the computational performance of the various methods in terms of their eeectiveness and eeciency on a standard set of problem instances. In the(More)
Suppose that an independence system (E, ) is characterized by a subroutine which indicates in unit time whether or not a given subset of E is independent. It is shown that there is no algorithm for generating all the K maximal independent sets of such an independence system in time polynomial in IEI and K, unless V. However, it is possible to apply ideas of(More)
The complexity of a class of vehicle routing and scheduling problems is investigated. We review known NP-hardness results and compile the results on the worst-case performance of approximation algorithms. Some directions for future research are suggested. The presentation is based on two discussion sessions during the Workshop to Investigate Future(More)