Net-length-based routability-driven power-aware clustering

Abstract

The state-of-the-art power-aware clustering tool, P-T-VPack, achieves energy reduction by localizing nets with high switching activity at the expense of channel width and area. In this study, we employ predicted individual postplacement net length information during clustering and prioritize longer nets. This approach targets the capacitance factor for energy reduction, and prioritizes longer nets for channel width and area reduction. We first introduce a new clustering strategy, W-T-VPack, which replaces the switching activity in P-T-VPack with a net length factor. We obtain a 9.87% energy reduction over T-VPack (3.78% increase over P-T-VPack), while at the same time completely eliminating P-T-VPack's channel width and area overhead. We then introduce W-P-T-VPack, which combines switching activity and net length factors. W-P-T-VPack achieves 14.26% energy reduction (0.31% increase over P-T-VPack), while further improving channel width by up to 12.87% for different cluster sizes. We investigate the energy performance of routability (channel width)-driven clustering algorithms, and show that W-T-VPack consistently outperforms T-RPack and iRAC by at least 11.23% and 9.07%, respectively. We conclude that net-length-based clustering is an effective method to concurrently target energy and channel width.

Integration of Net-Length Factor with Timing- and Routability-Driven Clustering Algorithms

“…These studies involved algorithm-level modifications to existing clustering strategies. In our most recent work [Easwaran and Akoglu 2011], we completed a detailed analysis on power-aware clustering and showed how the state-of-the-art power-aware clustering algorithm P-TVPack [Lamoureux and Wilton 2003] benefited from predicted individual net length on deciding which LUT to cluster into the CLB. This study showed that incorporating net-length information to the clustering cost function enabled the algorithm to prioritize longer nets, target the capacitance factor for power reduction, and, at the same time, eliminate the channel-width overhead of the P-T-VPack.…”