3 research outputs found
Scheduling two parallel machines with a single server: the general case
No full textThis paper considers the problem of scheduling two-operation non-preemptable jobs on two identical semi-automatic machines. A single server is available to carry out the first (or setup) operation. The second operation is executed automatically, without the server. The general problem of makespan minimization is NP-hard in the strong sense. In earlier work, we showed that the equal total length problem is polynomial time and we also provided efficient and effective solutions for the special cases of equal setup and equal processing times. Most of the cases analyzed thus far have fallen into the category of regular problems. In this paper we build on this earlier work to deal with the general case. Various approaches will be considered. One may reduce the problem to a regular one by amalgamating jobs, or we may apply the earlier heuristics to (possibly regular) job clusters. Alternately we may apply a greedy heuristic, a metaheuristic such as a genetic algorithm or the well known Gilmore-Gomory algorithm to solve the general problem. We report on the performance of these various methods
Equal processing and equal setup time cases of scheduling parallel machines with a single server
No full textThis paper considers the deterministic problem of scheduling two-operation non-preemptable jobs on two identical semi-automatic machines. A single server is available to carry out the first (or setup) operation. The second operation is executed automatically, without the server. The general problem of makespan minimization is NP-hard in the strong sense. Two special cases which arise in practice, the equal processing times and regular equal setup times problems turn out to be closely linked to the restricted set partitioning problem. This link is used to show that they are NP-hard in the ordinary sense, and to construct a tight lower bound and two highly effective O(n log n) heuristics
