Tabu Search Foundations: Additional Aspects of Short Term Memory

Abstract

We began the discussion of short term memory for tabu search in Chapter 2 by contrasting the TS designs with those of memoryless strategies such as simple or iterated descent, and by pointing out how candidate list strategies are especially important for applying TS in the most effective ways. We have deferred the discussion of such strategies in order to provide an understanding of some of the basic roles played by memory, and to illustrate the aggressive nature of decision criteria that typically are used to reinforce these roles. In this chapter we begin by describing types of candidate list strategies that often prove valuable in tabu search implementations. Then we examine the issues of logical restructuring, which provide important bridges to longer term considerations. Finally, we describe additional short term memory structures that build on the ideas used to apply TS memory to add/drop moves. We show how these ideas can be conveniently adapted to provide related structures for many different kinds of optimization problems, and associated neighborhoods for defining moves for these problems. These structures likewise provide a basis for incorporating longer term considerations.