Soft Variable Fixing in Path Relinking: An Application to ACO Codes

Soft variable fixing has emerged as one of the main techniques that the area of matheuristics can contribute to general metaheuristics. Recent years have in fact witnessed a fruitful interplay of methods that were originally proposed as general metaheuristcs with methods rooted in mathematic programming, which can be applied alone or as hybrids for solving combinatorial optimization problems. In this work, we show how one of the most effective matheuristics techniques, namely soft variable fixing, can be hybridized with Ant Colony Optimization. Specifically, we will combine a standard ACO code with a path relinking operator, implemented by means of soft variable fixing.