Formal Verification of Random Forests in Safety-Critical Applications

Abstract

Recent advances in machine learning and artificial intelligence are now being applied in safety-critical autonomous systems where software defects may cause severe harm to humans and the environment. Design organizations in these domains are currently unable to provide convincing arguments that systems using complex software implemented using machine learning algorithms are safe and correct. In this paper, we present an efficient method to extract equivalence classes from decision trees and random forests, and to formally verify that their input/output mappings comply with requirements. We implement the method in our tool VoRF (Verifier of Random Forests), and evaluate its scalability on two case studies found in the literature. We demonstrate that our method is practical for random forests trained on low-dimensional data with up to 25 decision trees, each with a tree depth of 20. Our work also demonstrates the limitations of the method with high-dimensional data and touches upon the trade-off between large number of trees and time taken for verification.