Self-organization in cooperative tabu search algorithms

The search history of memory based heuristics like tabu search can be used to design a category of parallel algorithms, called cooperative search. These algorithms execute in parallel several search programs on the same optimization problem instance. At run time, the data gathered in the memory by one sequential search program need not be used only by this program, but it can be recycled and shared with other concurrently executing tabu search programs for the same purpose. In this paper we compare the global behavior of cooperating and non-cooperating tabu search programs. We show that cooperating programs tend to have a search pattern which is less diversified than non-cooperating programs. Our findings also indicate that this second order impact of the sharing of gathered data on the search behaviors of cooperating programs is not related to the optimization properties of the individual tabu programs