Multilevel global placement with congestion control

Abstract

In this paper, we develop a multilevel global placement algorithm (MGP) integrated with fast incremental global routing for directly updating and optimizing congestion cost during physical hierarchy generation. Fast global routing is achieved 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 developed for placing objects with significant size variations. Experimental results show that, compared to GORDIAN-L, the wire length-driven MGP is 4-6.7 times faster and generates slightly better wire length for test circuits larger than 100000 cells. Moreover, the congestion-driven MGP improves wiring overflow by 45%-74% with 5% larger bounding box wire length but 3%-7% shorter routing wire length measured by a graph-based A-tree global router.