An Updated Assessment of Reinforcement Learning for Macro Placement

We provide an improved assessment of Google Brain’s deep reinforcement learning approach to macro placement [29] and its updated Circuit Training (CT) implementation in GitHub [53]. A stronger simulated annealing (SA) baseline leverages the “go-with-the-winners” metaheuristic [3] and a multi-threading implementation. We develop and release new public benchmarks in sub-10nm technology: LEF/DEF for Google’s 7nm TSMC Ariane protobuf and scaled variants, as well as testcases implemented in the open-source ASAP7 7nm research enablement. We evaluate from-scratch training and fine-tuning results for the latest “AlphaChip” release of Circuit Training, alongside multiple alternative macro placers. We also study the recently-published pre-training guidance in [53]. A commercial place-and-route tool is used to provide “true reward” post-route power, performance and area metrics. All data, evaluation flows and related scripts are publicly available in theMacroPlacementGitHub repository [63]. Our study affords insights into reproducibility and reporting in the research literature, and points out still-missing confirmations (e.g., of CT’s scalability and pre-training methodology) that remain open questions for the research community.