NN-SSTA: A deep neural network approach for statistical static timing analysis

摘要

Discrete statistical static timing analysis (SSTA) performs the timing analysis by using statistical maximum and convolution operations. The maximum is basically a non-linear operator and it is not a simple task to capture the skewness introduced by it. On the other hand, the convolution has a potential to "blow-up" the number of discrete samples as we going deep inside the timing graph and hence, results in exponential timing complexity. Therefore, in this paper we present novel deep neural network based operations which can accurately approximate the signal arrival-time's distributions with linear-time complexity. The various deep neural network (DNN) architectures have been used to implement both the maximum and the convolution operations using proper training dataset. Simulation results on various benchmark circuits (ISCAS 85, ISCAS 89, and ITC 99) show that the proposed method estimate the mean and standard deviation (STD) of critical path delay distribution with an average error of 0.75% and 2.56% as compared to Monte Carlo (MC), respectively. Our SSTA speeds up the traditional discrete approach by a factor of 20.7x on average. Furthermore, the PDF obtained from our method matches the ones obtained from MC with a reasonable error. Furthermore, we have proposed multi-wise maximum operations to reduce the arrival-time computational complexity at multi-inputs gates. Comparing to MC, the proposed method shows 0.97% and 2.58% average error in mean and STD respectively and the speeding up factor reaches 24.4x on average for all benchmarks. (C) 2020 Elsevier Ltd. All rights reserved.