Increasing interest has recently been shown in analyzing the worst-case behavior of local search algorithms. In particular, the quality of local optima and the time needed to find the local optima byâ€¦ (More)

We provide several non-approximability results for deterministic scheduling problems whose objective is to minimize the total job completion time. Unless P = NP, none of the problems underâ€¦ (More)

We investigate the problem of preemptively scheduling n jobs on m parallel machines. Whenever a machine switches from the processing of one job Jk to the processing of some other job Jj, a setup timeâ€¦ (More)

We investigate the multiprocessor multi stage open shop scheduling problem In this variant of the open shop model there are s stages each consisting of a number of parallel identical machines Eachâ€¦ (More)

We investigate a single-machine scheduling problem with precedence delays that have a simple structure: the corresponding tree has k leaves and only k + 2 nodes. The objective is to minimize theâ€¦ (More)

1 I n t r o d u c t i o n Chekuri, Hasan & Motwani [2] study the following problem tha t arises in the optimization of SQL queries for parallel machines: An operator graph G = (V, E) is a graph withâ€¦ (More)