Experiments with Scheduling Divisible Tasks in Clusters of Workstations Maciej Drozdowski 1⋆ and Pawe l Wolniewicz 2 1 Institute of Computing Science, Pozna´ n University of Technology, ul.Piotrowo 3a, 60-965 Pozna´ n, Poland. 2 Pozna´ n Supercomputing and Networking Center, ul.Noskowskiego 10, 61-794 Pozna´ n, Poland. Abstract. We present results of a series of experiments with parallel processing divisible tasks on various cluster of workstations platforms. Divisible task is a new model of scheduling distributed computations. It is assumed that the parallel application can be divided into parts of arbi- trary sizes and the parts can be processed independently on distributed computers. Though practical verification of the scheduling model was the primary goal of the experiments also an insight into the behavior and performance of cluster computing platforms has been gained. Keywords: Scheduling, divisible tasks, clusters of workstations. 1 Introduction The first work analyzing divisible tasks [3] was motivated by the need of finding optimal balance between parallelism of computations and necessary communi- cation in a linear network of intelligent sensors. Later divisible task model was used to represent distributed computations in: linear arrays of processors, stars, buses and trees of processors, hypercubes, meshes, multistage interconnections [1,4]. It was demonstrated that divisible task theory can be a useful tool in per- formance evaluation of distributed computations. Experiments performed in a dedicated Transputer system [2] confirm correctness of the theory predictions. This work is dedicated to verifying divisible task model in contemporary parallel processing environments available to the masses. The remaining parts of this paper are organized as follows. In the next sec- tion we formulate the problem of scheduling divisible task in star networks. In Section 3 we describe test applications. In Section 4 the way of experimenting and the results obtained are presented. In Section 5 the results are discussed and conclusions are proposed. ⋆ The research has been partially supported by a KBN grant and project CRIT2. Corresponding author. A. Bode et al. (Eds.): Euro-Par 2000, LNCS 1900, pp. 311–319, 2000. c  Springer-Verlag Berlin Heidelberg 2000