Routability Prediction and Optimization Using Explainable AI

Abstract

Machine learning (ML) techniques have been widely studied to predict routability in early-stage. To reduce the design turn-around time during the placement and routing iterations, it is crucial to predict the design rule violation (DRV) hotspots precisely before actual detailed routing. However, complex network architectures of ML make it challenging for humans to understand how ML generates predictions and to identify the factors that significantly influence the predictions. This black-box nature of ML limits the efficient integration of the prediction techniques into an optimization process. Explainable artificial intelligence enables the interpretation of decision rationales in the ML model and brings us the reasons underlying the prediction of the model. In this paper, we propose a routability optimization framework that analyzes the input features relevant to the predicted DRV hotspots using an explainable model and selects the most suitable optimization methods. The proposed framework comprises three steps - (1) predicting DRV hotspots in the early-global routing stage, (2) calculating how much each input feature contributes to the predictions and (3) applying a proper optimization method to improve the routability. We reduced the number of DRVs by 78% on average in 16 design layouts without degrading the design Quality.