Machine Learning for Testing Machine-Learning Hardware: A Virtuous Cycle

The ubiquitous application of deep neural networks (DNN) has led to a rise in demand for AI accelerators. DNN-specific functional criticality analysis identifies faults that cause measurable and significant deviations from acceptable requirements such as the inferencing accuracy. This paper examines the problem of classifying structural faults in the processing elements (PEs) of systolic-array accelerators. We first present a two-tier machine-learning (ML) based method to assess the functional criticality of faults. While supervised learning techniques can be used to accurately estimate fault criticality, it requires a considerable amount of ground truth for model training. We therefore describe a neural-twin framework for analyzing fault criticality with a negligible amount of ground-truth data. We further describe a topological and probabilistic framework to estimate the expected number of PE's primary outputs (POs) flipping in the presence of defects and use the PO-flip count as a surrogate for determining fault criticality. We demonstrate that the combination of PO-flip count and neural twin-enabled sensitivity analysis of internal nets can be used as additional features in existing ML-based criticality classifiers.