Case study for placement solutions in ISPD11 and DAC12 routability-driven placement contests

Routability is a critical issue in VLSI design flow. To address this issue, the routability-driven placement contests [1, 2] held at ISPD11 and DAC12 promote the development of routability-driven placers such as those in [4-6]. ISPD11 and DAC12 contests adopt metrics that are based on global routing solutions to evaluate the routability of placement solutions. However, such global-routing-based metrics typically ignore local congestion, and they cannot evaluate the actual routability effectively. In this work, we develop a translator that allows us to feed the placement solutions of mPL [3], NTUplace [4], Ripple [5], and SimPLR [6] into a commercial router for detailed routing. We then analyze the detailed routing result of each placement solution to better understand the issues that may cause routing violations. Moreover, we examine the suitability of using the ISPD11 and DAC12 metrics in predicting routability. Our findings indicated that the metrics might not reliably predict actual routability, in terms of the number of (detailed) routing violations.