Mwp Martin Savelsbergh

An efficient implementation of local search algorithms for constrained routing problems

We investigate the implementation of local search algorithms for routing problems with various side constraints such as time windows on vertices and precedence relations between vertices. The algorithms are based on the k-exchange concept. In the case of unconstrained routing problems, a single k-exchange can obviously be processed in constant time. In the presence of side constraints feasibility problems arise. Testing the feasibility of a single solution requires an amount of time that is linear in the number of vertices. We show how this effort can, on the average, still be reduced to a constant.

Behind the screen: DSS from an OR point of view

Interactive planning systems are a relatively new phenomenon in the practice of operations research. We review the role of quantitative models and methods and the need for man-machine interaction in practical planning situations. We specify a number of desirable functional requirements of an interactive planning system, and discuss the graphical user interface and the use of various representations. We comment on the types of solution strategies involved and relate some of our own experience.