Pre-Routing Path Delay Estimation Based on Transformer and Residual Framework

Timing estimation prior to routing is of vital importance for optimization at placement stage and timing closure. Existing wire- or net-oriented learning-based methods limits the accuracy and efficiency of prediction due to the neglect of the delay correlation along path and computational complexity for delay accumulation. In this paper, an efficient and accurate pre-routing path delay prediction framework is proposed by employing transformer network and residual model, where the timing and physical information at placement stage is extracted as sequence features while the residual of path delay is modeled to calibrate the mismatch between the pre- and post-routing path delay. Experimental results demonstrate that with the proposed framework, the prediction error of post-routing path delay is less than 1.68% and 3.12% for seen and unseen circuits in terms of rRMSE, which is reduced by 2.3~5.0 times compared with exiting learning-based method for pre-routing prediction. Moreover, this framework produces at least three orders of magnitude speedup compared with the traditional design flow, which is promising to guide circuit optimization with satisfying prediction accuracy prior to time-consuming routing and timing analysis.