Communication Performance of Wormhole Interconnection Networks

Fat trees and low dimensional toroidal cubes have raised a great interest in the scientiic community in the last few years and are emerging standards in the design of interconnection networks for massively parallel computers. In this thesis we compare the communication performance of these two classes of wormhole interconnection networks using a detailed simulation model. The comparison is made using a set of synthetic benchmarks and two collective communication patterns, the total-exchange and the h-relation, taking into account physical constraints, as pin and bandwidth limitations, and the router complexity. In our experiments we consider two networks with 256 nodes, a toroidal 16-ary 2-cube and 4-ary 4-tree. We also show an interesting property that relates the communication performance of the fat trees with the network abstraction provided by the Bulk-Synchronous Parallel (BSP) model. This property can be used to give a tight upper bound on the execution of many classes of h-relations. Acknowledgments Many people have helped me to make the years spent in Pisa some of the most signiicant of my life. Marco Vanneschi, my advisor, deserves special thanks not only due to his invaluable support, teaching, and guidance in his role as my advisor, but also for the supportive way he has helped me through the diicult moments of my thesis. The members of the P 3 L group have ooered their help and their advice. Special thanks go to A special thank goes to my reviewers, Prof. Jos e Duato and Prof. David B. Skillicorn for their help in improving the quality of the thesis and their comments. I am also indebt to Federico Malucelli for his friendship and insightful advice during the last period of my thesis. Finally, my parents have been an endless source of support, love, and encouragement. Without their guidance and motivation I would never have come so far.