A Hybrid Seachr Architecture Applied to Hard Random 3-SAT and Low-Autocorrelation Binary Sequences

  • Authors:

  • Steven David Prestwich

  • Affiliations:

  • -

  • Venue:
  • CP '02 Proceedings of the 6th International Conference on Principles and Practice of Constraint Programming
  • Year:
  • 2000

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Abstract

The hybridisation of systematic and stochastic search is an active research area with potential benefits for real-world combinatorial problems. This paper shows that randomising the backtracking component of a systematic backtracker can improve its scalability to equal that of stochastic local search. The hybrid may be viewed as stochastic local search in a constrained space, cleanly combininglo cal search with constraint programming techniques. The approach is applied to two very different problems. Firstly a hybrid of local search and constraint propagation is applied to hard random 3-SAT problems, and is the first constructive search algorithm to solve very large instances. Secondly a hybrid of local search and branch-and-bound is applied to low-autocorrelation binary sequences (a notoriously difficult communications engineering problem), and is the first stochastic search algorithm to find optimal solutions. These results show that the approach is a promising one for both constraint satisfaction and optimisation problems.