Heuristic Techniques in Project Sequencing

One of the problems faced by planners when designed an expansion plan for water resources systems is selecting the sequence of projects that satisfies a given demand at minimum cost, some prescribed time into the future. This problem is indeed closely related to what is generally known as the capacity expansion problem although unique local conditions at each project site result in a somewhat different problem formulation. To ensure an optimal solution to the project sequencing problem the usual approach has been to use dynamic programming techniques, although it suffers from the commonly known limits on problem size due to the associated excessive computational requirements. The need of planners in search of a practical screening method useful at all stages in the planning process, involving possibly a large number of projects, has led to the introduction of several heuristic algorithms. While such algorithms do not guarantee an optimal solution, their usefulness is based on the assumption that the solution obtained is close enough to being optimal for some practical purposes. Little has, however, been written about their performance in general. This paper deals with performance evaluation of several such algorithms. The algorithms are tested by creating a number of sequencing problems which are in turn solved by each of them as well as by dynamic programming. By keeping track of each algorithms performance for varying assumptions such as the shape of the demand function and the cost-capacity characteristics for individual projects, a performance profile is established for each algorithm. Such performance measure should be helpful when selecting the appropriate solution procedure to a project-sequencing problem for instance in a practical setting. Presented at NOAK 1980 The 9 Nordic Congress on Operations Research September 18-19, 1980 REYKJAVIK, ICELAND © 1980 Egill B. Hreinsson 2TABLE OF CONTENTS Abstract: ..................................................................... 1