Searching for Bugs Using Probabilistic Suspect Implications

Due to the excessive cost associated with manual RTL design debugging, automated tools are often employed to identify a set of suspect bug locations. To further accelerate the process, one observes that the anytime behavior of these tools allows partial results to be analyzed before the suspect search is complete. Thus, it is preferable for the tool to maximize the number of suspects that are found in the early stages of its search. Toward this end, this article proposes a new SAT-based debugging algorithm which predicts where solutions are most likely to be found and prioritize examining these locations. Two techniques are proposed to predict solution locations by learning from historical debug data. The first technique does so using belief propagation on a probabilistic graph, while the second trains a neural network to classify candidate suspects as solutions or nonsolutions. Intensive empirical evaluation demonstrates that these techniques can predict suspect sets with accuracies of 81% and 87%, respectively, but the second method requires more training data and careful hyperparameter tuning in order to do so. Furthermore, when guided by these suspect prediction models, the proposed debugging algorithm finds an average of 83% more suspects within a given amount of time.