Net Resource Allocation: A Desirable Initial Routing Step
Zhisheng Zeng, Jikang Liu, Zhipeng Huang, Ye Cai, Biwei Xie, Yungang Bao, Xingquan Li · 2024
In modern IC design, routing significantly impacts chip performance, power, area, and design iteration count. Critical challenges in routing include generating a rectilinear Steiner minimum tree (RSMT) for each net and handling routing resources among nets. Due to limited resources and net order, congestion is inevitable in VLSI circuit routing. Most competitive routers address congestion after routing without prior net guidance, leading to difficulty in managing resources among nets. We suggest introducing a net resource allocation step to tackle routing and congestion as a potentially desirable initial routing stage. Firstly, we introduce the net region probability density (NRPD) concept to achieve suitable net resource allocation. Using a prior NRPD, we model the resource allocation problem as linear programming (LP). We solve the LP problem and obtain a posterior NRPD for each net on each grid. Based on the posterior NRPD and congestion map, we introduce a cost scheme to guide net routing. This cost scheme supports a weighted RSMT construction technique for better topological solutions. We propose an iterative method for global routing and track assignment, improving detailed routing quality and optimizing design rule violations. Experimental results show the effectiveness of net resource allocation and demonstrate the superior performance of our router over OpenROAD's router across multiple metrics.