Showing papers on "Greedy algorithm published in 1977"

Analysis of a switch matrix for an SS/TDMA system

Abstract: Time slot scheduling problem for a satellite switched/time-division multiple access (SS/TDMA) system is discussed and an algorithm called "Greedy Algorithm" is presented. This algorithm guarantees a most efficient utilization of a frame period with n2- n (n is the number of beams) number of switchings at most. Another problem discussed in this paper is the choice of the type of microwave switch matrix to be put on board the satellite. A switch-matrix structure called rearrangeable multistage matrix is shown to have high reliability and low-insertion-loss characteristics. Also brief discussions are made on the experimental results of an engineering model SS/TDMA system.

Technical Note—An Effective Heuristic for the M-Tour Traveling Salesman Problem with Some Side Conditions

Abstract: This note presents a heuristic for determining very good solutions for the symmetric M-tour traveling salesman problem with some side conditions. These side conditions' pertain to load, distance and time, or sequencing restrictions. The heuristic is an extension of the highly successful one of Lin and Kernighan for the single traveling salesman problem. Computational experience with widely tested vehicle dispatch problems indicates that the proposed heuristic consistently yields better solutions than existing heuristics that have appeared in the literature. Run times grow approximately as N2.3, where N is the number of cities. The heuristic is generally slower than the modified SWEEP heuristic except on problems having a large number of points per route.

Evaluating a Sequential Vehicle Routing Algorithm

Abstract: The Clarke-Wright algorithm is a heuristic algorithm which has been implemented frequently and successfully to solve large-scale vehicle routing problems. In this paper, we focus on evaluating the accuracy of the Clarke-Wright procedure in its sequential form. We present examples of pathological behavior and suggest algorithm modifications to help overcome these problems.

Error Bounds and the Applicability of the Greedy Solution to the Coin-Changing Problem

Abstract: Necessary and sufficient conditions have been given that characterize the data for which a greedy algorithm solves the coin-changing problem. In this paper we study the problem of maximum percentage error when the greedy solution does not work. We also generalize a result of Johnson and Kernighan to the case for which each coin is of different weight.

Some Partial Orders Related to Boolean Optimization and the Greedy Algorithm

Abstract: For B = {0,1} and ordered sets (H, ⩽) the objective f : Bn →H shall be maximized under the restriction x ɛS ⊆Bn, The Greedy algorithm can be formulated for this problem without difficulties. The question is for which objectives f and which restrictions S one can use the algorithm to solve the above defined Boolean optimization problem. Dealing with this question, it turned out to be useful to replace the objective by a preorder. The problem then is to determine a maximum of a given preorder on Bn in S ⊆Bn. Concerning some partial orders on Bn problems are characterized for which the optimal solution does not depend on the special choice of the objective. Assumptions with regard to S are closely related to matroid theory; in view of the preorder a certain monotonicity condition is important. The dual greedy algorithm and a modified form of it leads us to the definition of dual partial orders. Herewith it is possible to characterize those S ⊆Bn for which the greedy algorithm and its dual determine the same vector.