Physical hierarchy generation with routing congestion control

Abstract

In this paper, we develop a multi-level physical hierarchy generation (mPG) algorithm integrated with fast incremental global routing for directly updating and optimizing congestion cost during placement. The fast global routing is achieved by using a fast two-bend routing and incremental A-tree algorithm. The routing congestion is modeled by the wire usage estimated by the fast global router. A hierarchical area density control is also developed for placing objects with significant size variations. Experimental results show that, compared to Gordian-L, the wire length driven mPG is 3-6.5 times faster and generates slightly better wire length for test circuits larger than 100K cells. Moreover, the congestion driven mPG improves 50% wiring overflow with 5% larger bounding box wire length but 3-6% shorter routing wire length measured by graph based A-tree.