To Rip or not to Rip: A Reinforcement Learning-based Rip-up and Reroute Algorithm for Global RoutingDownload PDF

Dec 14, 2020 (edited Dec 26, 2020)CUHK 2021 Course IERG5350 Blind SubmissionReaders: Everyone
  • Keywords: Routing, Reinforcement Learning, EDA
  • Abstract: Routing, including global routing and detailed routing, has been a critical step in the design of integrated circuits. Most of the existing global routers will firstly use techniques like pattern routing and layer assignment to quickly generate a routing solution and optimize total wirelength and via usage. Then rip-up and reroute (RRR) scheme will be applied to iteratively reduce the number of overflows in the whole design. However, compared with initial routing stage, RRR will be much more time consuming. It will rip up all the nets that pass through overflowed area and reroute them sequentially. Even if the routing resources in one routing cell is overused by 1, the router will rip up all the nets that are routed on the routing cell, as it does not know which net will be the best choice to rip up. In this way, RRR may be doing a lot of redundant work. Besides, some initial routing solutions that are optimal in terms of wirelength will also be wasted when they are ripped up, causing a loss of routing quality. Therefore, in this project, we propose to use reinforcement learning to help decide which nets to rip up in each RRR iterations. An actor-critic based Proximal Policy Optimization (PPO) agent is trained for this task. Experimental results show that the proposed approach can successfully reduce the number of rerouted nets with little loss of routing quality on the ICCAD’19 global routing contest benchmarks, which demonstrate the effectiveness of our model.
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