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International Journal of Reconfigurable Computing
Volume 2011 (2011), Article ID 745147, 14 pages
Research Article

An NoC Traffic Compiler for Efficient FPGA Implementation of Sparse Graph-Oriented Workloads

1Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2AZ, UK
2Department of Electrical and Systems Engineering, University of Pennsylvania, Philadelphia, PA 19104, USA

Received 28 August 2010; Accepted 14 December 2010

Academic Editor: Michael Hübner

Copyright © 2011 Nachiket Kapre and André Dehon. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Parallel graph-oriented applications expressed in the Bulk-Synchronous Parallel (BSP) and Token Dataflow compute models generate highly-structured communication workloads from messages propagating along graph edges. We can statially expose this structure to traffic compilers and optimization tools to reshape and reduce traffic for higher performance (or lower area, lower energy, lower cost). Such offline traffic optimization eliminates the need for complex, runtime NoC hardware and enables lightweight, scalable NoCs. We perform load balancing, placement, fanout routing, and fine-grained synchronization to optimize our workloads for large networks up to 2025 parallel elements for BSP model and 25 parallel elements for Token Dataflow. This allows us to demonstrate speedups between 1.2× and 22× (3.5× mean), area reductions (number of Processing Elements) between 3× and 15× (9× mean) and dynamic energy savings between 2× and 3.5× (2.7× mean) over a range of real-world graph applications in the BSP compute model. We deliver speedups of 0.5–13× (geomean 3.6×) for Sparse Direct Matrix Solve (Token Dataflow compute model) applied to a range of sparse matrices when using a high-quality placement algorithm. We expect such traffic optimization tools and techniques to become an essential part of the NoC application-mapping flow.