LOCAL++: A C++ Framework for Local Search Algorithms

Local search is an emerging paradigm for combinatorial search which has been recently shown to be very e ective for a large number of combinatorial problems. It is based on the idea of navigating the search space by iteratively stepping from one solution to one of its neighbors, which are obtained by applying a simple local change to it. In this paper we present Local++, an object-oriented framework to be used as a general tool for the development and the implementation of local search algorithms in C++. The framework comprises a hierarchy of abstract template classes, one for each local search technique taken into account (i.e., hill-climbing, simulated annealing, and tabu search). Each class speci es and implements the invariant part of the algorithm built according to the technique, and is supposed to be specialized by a concrete class once a given search problem is considered, so as to implement the problem-dependent part of the algorithm. Local++ comprises also a set of abstract classes for creating new techniques by combining di erent search techniques and di erent neighborhood relations. The architecture of Local++ provides a principled modularization for the solution of combinatorial search problems, and helps the designer deriving a neat 1 conceptual scheme of the application, thus facilitating the development and debugging phases. Local++ proved to be exible enough for the implementation of the algorithms solving various scheduling problems.