Models and Strategies for Variants of the Job Shop Scheduling Problem

Recently, a variety of constraint programming and Boolean satisfiability approaches to scheduling problems have been introduced. They have in common the use of relatively simple propagation mechanisms and an adaptive way to focus on the most constrained part of the problem. In some cases, these methods compare favorably to more classical constraint programming methods relying on propagation algorithms for global unary or cumulative resource constraints and dedicated search heuristics. In particular, we described an approach that combines restarting, with a generic adaptive heuristic and solution guided branching on a simple model based on a decomposition of disjunctive constraints. In this paper, we introduce an adaptation of this technique for an important subclass of job shop scheduling problems (JSPs), where the objective function involves minimization of earliness/tardiness costs. We further show that our technique can be improved by adding domain specific information for one variant of the JSP (involving time lag constraints). In particular we introduce a dedicated greedy heuristic, and an improved model for the case where the maximal time lag is 0 (also referred to as no-wait JSPs).Comment: Principles and Practice of Constraint Programming - CP 2011, Perugia : Italy (2011

Scheduling models for short-term railway traffic optimisation

In this paper we report on the results of a research project on train traffic control systems, supported by the European Commission. The results of the project include the development of new optimisation models and algorithms for traffic management, and a general architecture for train traffic control, capable of managing both fixed block and moving block signaling safety concepts. This paper focuses in particular on models and algorithms for real time conflict resolution. Computational results are reported, based on a portion of the Dutch railway network, on the high-speed line Paris-Brussels-Amsterdam