Randomized partially-minimal routing: near-optimal oblivious routing for 3-D mesh networks

  • Authors:
  • Rohit Sunkam Ramanujam;Bill Lin

  • Affiliations:
  • Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA;Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, CA

  • Venue:
  • IEEE Transactions on Very Large Scale Integration (VLSI) Systems
  • Year:
  • 2012

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Abstract

The increasing viability of 3-D silicon integration technology has opened new opportunities for chip architecture innovations. One direction is in the extension of 2-D mesh-based tiled chip-multiprocessor architectures into three dimensions. This paper focuses on efficient routing algorithms for such 3-D mesh networks. Existing routing algorithms suffer from either poor worst-case throughput (DOR, ROMM) or poor latency (VAL). Although the minimal routing algorithm O1TURN proposed in already achieves near-optimal worst-case throughput for 2-D mesh networks, the optimality result does not extend to higher dimensions. For 3-D and higher dimensional meshes, the worst-case throughput of O1TURN degrades tremendously. The main contribution of this paper is a new oblivious routing algorithm for 3-D mesh networks called randomized partially-minimal (RPM) routing. RPM provably achieves optimal worst-case throughput for 3-D meshes when the network radix k is even and within a factor of 1/k2 of optimal worst-case throughput when k is odd. Finally, whereas VAL achieves optimal worst-case throughput at a penalty factor of 2 in average latency over DOR, RPM achieves (near) optimal worst-case throughput with a much smaller factor of 1.33. For practical asymmetric 3-D mesh configurations where the number of device layers are fewer than the number of tiles along the edge of a layer, the average latency of RPM reduces to just a factor of 1.11 to 1.19 of DOR. Additionally, a variant of RPM called randomized minimal first (RMF) routing is proposed, which leverages the inherent load-balancing properties of the network traffic to further reduce packet latency without compromising throughput.