A multi-model algorithm for the cost-oriented design of Internet-based systems

The selection of a cost-minimizing combination of hardware and network components of Internet-based systems to satisfy organizational requirements is a complex design problem with multiple degrees of freedom. Decisions must be made on how to distribute the overall computing load onto multiple computers, where to locate computers and how to take advantage of legacy components. The corresponding optimization problem not only embeds the structure of NP-hard problems, but also represents a challenge with a well-structured heuristic approach. A scientific approach has been rarely applied to cost minimization and a rigorous methodological support to cost issues of the design of Internet-based distributed systems is still lacking. The methodological contribution of this paper is the representation of complex design issues as a set of four intertwined cost-minimization sub-problems: two set-partitionings, a set-packing and a min k-cut with a non-linear objective function. Optimization is accomplished by sequentially solving these sub-problems with a heuristic approach and tuning their solution with a local-search approach. Results indicate that decomposition significantly reduces optimization time and solutions have also lower costs than those identified without prior decomposition (20-60%). Cost reductions considerably grow (25-70%) when methodological outputs are compared with practitioners' solutions.