On Obtaining Non-Similar Solutions from Similar Solutions

AbstractLocal search is a fundamental tool in the development of heuristic algorithms. A neighborhood operator takes a current solution and returns a set of similar solutions, denoted as neighbors. In best improvement local search, the best of the neighboring solutions replaces the current solution in each iteration. On the other hand, in first improvement local search, the neighborhood is only explored until any improving solution is found, which then replaces the current solution. In this work we propose a new strategy for local search that attempts to avoid low-quality local optima by selecting in each iteration the improving neighbor that has the fewest possible attributes in common with local optima. To this end, it uses inequalities previously used as optimality cuts in the context of integer linear programming. The novel method, referred to as delayed improvement local search, is implemented and evaluated using the travelling salesman problem with the 2-opt neighborhood and the max-cut problem with the 1-flip neighborhood as test cases. Computational results show that the new strategy, while slower, obtains better local optima compared to the traditional local search strategies. The comparison is favourable to the new strategy in experiments with fixed computation time or with a fixed target.

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A laser experiment for studying radiative shocks in astrophysics

Laser and Particle Beams ◽

10.1017/s0263034602202165 ◽

2002 ◽

Vol 20 (2) ◽

pp. 263-268 ◽

Cited By ~ 42

Author(s):

X. FLEURY ◽

S. BOUQUET ◽

C. STEHLÉ ◽

M. KOENIG ◽

D. BATANI ◽

...

Keyword(s):

Laser Pulse ◽

Pulse Duration ◽

Experimental Results ◽

Laboratory Astrophysics ◽

Laser Pulse Duration ◽

Radiative Shocks ◽

Self Similar ◽

Laser Experiment ◽

Similar Solutions

In this article, we present a laboratory astrophysics experiment on radiative shocks and its interpretation using simple modelization. The experiment is performed with a 100-J laser (pulse duration of about 0.5 ns) which irradiates a 1-mm3 xenon gas-filled cell. Descriptions of both the experiment and the associated diagnostics are given. The apparition of a radiation precursor in the unshocked material is evidenced from interferometry diagrams. A model including self-similar solutions and numerical ones is derived and fairly good agreements are obtained between the theoretical and the experimental results.

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