Scaling up Memory-Efficient Formal Verification Tools for Tree Ensembles

Abstract

To guarantee that machine learning models yield outputs that are not only accurate, but also robust, recent works propose formally verifying robustness properties of machine learning models. To be applicable to realistic safety-critical systems, the used verification algorithms need to manage the combinatorial explosion resulting from vast variations in the input domain, and be able to verify correctness properties derived from versatile and domain-specific requirements. In this paper, we formalise the VoTE algorithm presented earlier as a tool description, and extend the tool set with mechanisms for systematic scalability studies. In particular, we show a) how the separation of property checking from the core verification engine enables verification of versatile requirements, b) the scalability of the tool, both in terms of time taken for verification and use of memory, and c) that the algorithm has attractive properties that lend themselves well for massive parallelisation. We demonstrate the application of the tool in two case studies, namely digit recognition and aircraft collision avoidance, where the first case study serves to assess the resource utilisation of the tool, and the second to assess the ability to verify versatile correctness properties.

Formal Verification of Tree Ensembles in Safety-Critical Applications

“…In this work, we leverage one of these algorithms, implemented in the tool suite VoTE (Törnblom & Nadjm-Tehrani, 2019), to construct an oracle that is both sound and complete. VoTE has demonstrated great performance in terms of runtime and memory usage (Törnblom & Nadjm-Tehrani, 2021), and provides a modular property checking interface realized as a recursive higher-order function. More specifically, VoTE accepts three parameters as input; a tree ensemble F , a tuple of intervals X ∈ I n with ⊥ ∈ X, and a property checker pc : I n × I m → {P ass, F ail, U nsure}, as formalized by Algorithm 4.…”