Archer: a history-driven global routing algorithm

Global routing is an important step in the physical design process. In this paper, we propose a new global routing algorithm Archer, which resolves some of the most common problems with the state-of-the-art global routers. It is known that concurrent global routing algorithms are typically too expensive to be applied on today´s large designs, which may contain up to a million nets. On the other hand, iterative rip-up and reroute (RNR) based algorithms are susceptible to getting stuck in local optimal solutions. In this paper, we propose an RNR-based global routing algorithm that guides the routing iterations out of local optima through effective usage of congestion histories. We also focus on the problem of how to enable a smooth trade-off between seemingly conflicting objectives of overflow and wirelength minimization. Furthermore, we propose a Lagrangian relaxation based bounded-length min-cost topology improvement algorithm that enables Steiner trees to change dynamically for the purpose of congestion optimization. Our experiments show that Archer obtains congestion-free solutions for all circuits in the standard ISPD98 benchmarks, which is the best result published so far. Furthermore, it produces better results than the best results reported in the ISPD-07 Global Routing Contest in terms of routability. Compared to FastRoute (Paa & Chu), which is the state-of-the-art RNR-based global routing algorithm, Archer improves routability by 30%, and reduces the wire lengths by 32% on the average on ISPD07 benchmarks.