Copyright Notice:

The documents distributed by this server have been provided by the contributing authors as a means to ensure timely dissemination of scholarly and technical work on a noncommercial basis. Copyright and all rights therein are maintained by the authors or by other copyright holders, notwithstanding that they have offered their works here electronically. It is understood that all persons copying this information will adhere to the terms and constraints invoked by each author's copyright. These works may not be reposted without the explicit permission of the copyright holder.

Publications of SPCL

T. Hoefler, T. Schneider, A. Lumsdaine:

 Multistage Switches are not Crossbars: Effects of Static Routing in High-Performance Networks

(. Vol , Nr. , In Proceedings of the 2008 IEEE International Conference on Cluster Computing, presented in Tsukuba, Japan, pages , IEEE Computer Society, ISSN: 1552-5244, ISBN: 978-1-4244-2640, Oct. 2008)


Multistage interconnection networks based on central switches are ubiquitous in high-performance computing. Applications and communication libraries typically make use of such networks without consideration of the actual internal characteristics of the switch. However, application performance of these networks, particularly with respect to bisection bandwidth, does depend on communication paths through the switch. In this paper we discuss the limitations of the hardware definition of bisection bandwidth (capacity-based) and introduce a new metric: effective bisection bandwidth. We assess the effective bisection bandwidth of several large-scale production clusters by simulating artificial communication patterns on them. Networks with full bisection bandwidth typically provided effective bisection bandwidth in the range of 55-60%. Simulations with application-based patterns showed that the difference between effective and rated bisection bandwidth could impact overall application performance by up to 12%.


download article:
download slides:


  author={Torsten Hoefler and Timo Schneider and Andrew Lumsdaine},
  title={{Multistage Switches are not Crossbars: Effects of Static Routing in High-Performance Networks}},
  booktitle={Proceedings of the 2008 IEEE International Conference on Cluster Computing},
  location={Tsukuba, Japan},
  publisher={IEEE Computer Society},