We describe a new neighborhood structure for the capacitated minimum spanning tree problem. This neighborhood structure is used by a local search strategy, leading to good trade-offs between solution quality and computation time. We also propose a GRASP with path-relinking heuristic. It uses a randomized version of a savings heuristic in the construction phase and an extension of the above loca...

In a railroad system, train pathing is concerned with the assignment of trains to links and tracks, and train timetabling allocates time slots to trains. In this paper, we present an optimization heuristic to solve the train pathing and timetabling problem. This heuristic allows the dwell time of trains in a station or link to be dependent on the assigned tracks. It also allows the minimum clea...

We report a general phenomenon concerning the effect of noise on phase synchronization in coupled chaotic oscillators: the average phase-synchronization time exhibits a nonmonotonic behavior with the noise amplitude. In particular, we find that the time exhibits a local minimum for relatively small noise amplitude but a local maximum for stronger noise. We provide numerical results, experimenta...

This paper describes a general framework for the retiming of sequential circuits using either single or multi-phase clocks and both edge-ttiggered flip-flops and level-sensitive latches. This framework is compared with previously published work on retiming. The potential for finding optimal retimings within this framework is discussed, and a set of heuristic retim­ ing methods is presented. Fin...

Memory-based heuristic techniques have been used to effectively reduce search times in implicit graphs. Recently, these techniques have been applied to improving search times in explicit graphs. This paper presents a new memory-based, additive heuristic that can be used on a type of explicit graph: the four-connected gridworld. The heuristic reduces the number of expanded nodes by up to five ti...

By considering the task of finding the shortest walk through a network we find an algorithm for which the run time is not as O(2n), with n being the number of nodes, but instead scales with the number of nodes in a coarsened network. This coarsened network has a number of nodes related to the number of dense regions in the original graph. Since we exploit a form of local community detection as ...

This paper is devoted to the numerical resolution of unit-commitment problems. More precisely we present the French model optimizing the daily production of electricity. Its resolution is done is two phases: first a Lagrangian relaxation solves the dual to find a lower bound; it also gives a primal relaxed solution. The latter is used in the second phase for a heuristic resolution based on a pr...

Optimization in sports is a field of increasing interest. Combinatorial optimization techniques have been applied e.g. to game scheduling and playoff elimination. A common problem usually found in sports management is the assignment of referees to games already scheduled. There are a number of rules and objectives that should be taken into account when referees are assigned to games. We address...