Parallel simulated annealing for the covering arrays construction problem

A covering array (CA) is a combinatorial structure specified as a matrix of N rows andk columns over an alphabet onv symbols such that for each set of t columns everyt-tuple of symbols is covered at least once. Given the values oft, k, andv, the optimal covering array construction problem (CAC) consists in constructing a CA(N ; t, k, v) with the minimum possible value of N . There are several reported methods to attend the CAC problem, among them are: direct methods, recursive methods, greedy methods, and metaheuristics methods. In this paper, three parallel approaches for simulated annealing, i.e. the independent, semi-independent and cooperative searches are applied to the CAC problem. The empirical evidence supported by statistical analysis indicate that the cooperative approa ch offers the best execution times and the same upper bounds than the independent and semi-independent approaches. Extensive experimentation was carried out, using 96 wellknown benchmark instances, for assessing its performance with respect to the best-known bounds reported previously. The results show that cooperative approach attains 78 new bounds and equals the solutions for other 6 instances.