Abstract
Efficient verification algorithms for neural networks often depend on various abstract domains such as intervals, zonotopes, and linear star sets. The choice of the abstract domain presents an expressiveness vs. scalability trade-off: simpler domains are less precise but yield faster algorithms. This paper investigates the hexatope and octatope abstract domains in the context of neural net verification. Hexatopes are affine transformations of higher-dimensional hexagons, defined by difference constraint systems, and octatopes are affine transformations of higher-dimensional octagons, defined by unit-two-variable-per-inequality constraint systems. These domains generalize the idea of zonotopes which can be viewed as affine transformations of hypercubes. On the other hand, they can be considered as a restriction of linear star sets, which are affine transformations of arbitrary \(\mathcal {H}\)-Polytopes. This distinction places hexatopes and octatopes firmly between zonotopes and linear star sets in their expressive power, but what about the efficiency of decision procedures? An important analysis problem for neural networks is the exact range computation problem that asks to compute the exact set of possible outputs given a set of possible inputs. For this, three computational procedures are needed: (1) optimization of a linear cost function; (2) affine mapping; and (3) over-approximating the intersection with a half-space. While zonotopes allow an efficient solution for these approaches, star sets solves these procedures via linear programming. We show that these operations are faster for hexatopes and octatopes than they are for the more expressive linear star sets by reducing the linear optimization problem over these domains to the minimum cost network flow, which can be solved in strongly polynomial time using the Out-of-Kilter algorithm. Evaluating exact range computation on several ACAS Xu neural network benchmarks, we find that hexatopes and octatopes show promise as a practical abstract domain for neural network verification.







Similar content being viewed by others
Data availability
Data is available upon request.
References
Ahuja RK, Magnanti TL, Orlin JB (1993) Network flows: theory, algorithms, and applications. Prentice Hall, Upper Saddle River
Akintunde M, Lomuscio A, Maganti L, Pirovano E (2018). Reachability analysis for neural agent-environment systems. In: 16th international conference on principles of knowledge representation and reasoning
Albarghouthi A (2021) Introduction to neural network verification. http://verifieddeeplearning.com
Bak S (2021) nnenum: verification of ReLU neural networks with optimized abstraction refinement. In: NASA formal methods symposium, pp 19–36. Springer
Bak S, Dohmen T, Subramani K, Trivedi A, Velasquez A, Wojciechowski P (2023) The octatope abstract domain for verification of neural networks. In: Chechik M, Katoen J-P, Leucker M (eds), Formal methods—25th international symposium, FM 2023, Lübeck, Germany, March 6-10, 2023, Proceedings, volume 14000 of Lecture Notes in Computer Science, pp 454–472. Springer
Bak S, Liu C, Johnson T (2021) The second international verification of neural networks competition (VNN-comp 2021): summary and results. arXiv:2109.00498
Bak S, Tran H-D, Hobbs K, Johnson TT (2020) Improved geometric path enumeration for verifying Relu neural networks. In: Proceedings of the 32nd international conference on computer aided verification. Springer
Baluta T, Shen S, Shinde S, Meel KS, Saxena P (2019) Quantitative verification of neural networks and its security applications. In: Proceedings of the 2019 ACM SIGSAC conference on computer and communications security, pp 1249–1264
Bazaraa MS, Jarvis JJ, Sherali HD (2008) Linear programming and network flows. Wiley, New York
Behrmann G, David A, Larsen KG, Håkansson J, Pettersson P, Yi W, Hendriks M (2006) UPPAAL 4.0. In: 3rd international conference on the quantitative evaluation of systems (QEST 2006), 11-14 September 2006, Riverside, California, USA, pp 125–126. IEEE Computer Society
Biswas S, Rajan H (2023) Fairify: fairness verification of neural networks. In: 2023 IEEE/ACM 45th international conference on software engineering (ICSE), pp 1546–1558. IEEE
Casadio M, Komendantskaya E, Daggitt ML, Kokke W, Katz G, Amir G, Refaeli I (2022) Neural network robustness as a verification property: a principled case study. In: International conference on computer aided verification, pp 219–231. Springer
Cohen MB, Lee YT, Song Z (2021) Solving linear programs in the current matrix multiplication time. J ACM 68(1):3:1-3:39
Cormen TH, Leiserson CE, Rivest RL, Stein C (2009) Introduction to algorithms, 3rd edn. MIT Press, Cambridge
Cousot P, Cousot R (1977) Abstract interpretation: A unified lattice model for static analysis of programs by construction or approximation of fixpoints. In: Proceedings of the 4th ACM SIGACT-SIGPLAN symposium on principles of programming languages, POPL ’77, pp 238–252, New York, NY, USA. Association for Computing Machinery
De Moura L, Bjørner N (2008). Z3: an efficient SMT solver. In: International conference on tools and algorithms for the construction and analysis of systems, pp 337–340. Springer
Duggirala PS, Viswanathan M (2016). Parsimonious, simulation based verification of linear systems. In: International conference on computer aided verification, pp 477–494. Springer
Friedmann O, Hansen TD, Zwick U (2011) Subexponential lower bounds for randomized pivoting rules for the simplex algorithm. In: Symposium on theory of computing, STOC’11, pp 283–292, New York, NY, USA. ACM
Gehr T, Mirman M, Drachsler-Cohen D, Tsankov P, Chaudhuri S, Vechev M (2018). Ai2: safety and robustness certification of neural networks with abstract interpretation. In: 2018 IEEE symposium on security and privacy (SP), pp 3–18. IEEE
Ghorbal K, Goubault E, Putot S (2009). The zonotope abstract domain Taylor1+. In: International conference on computer aided verification, pp 627–633. Springer
Goldberg AV, Tarjan RE (1989) Finding minimum-cost circulations by canceling negative cycles. J ACM 36(4):873–886
Henriksen P, Lomuscio A (2020). Efficient neural network verification via adaptive refinement and adversarial search. In: ECAI 2020, pp 2513–2520. IOS Press
Henriksen P, Lomuscio A (2021). Deepsplit: an efficient splitting method for neural network verification via indirect effect analysis. In: Proceedings of the 30th international joint conference on artificial intelligence (IJCAI21), To appear
Huang X, Kroening D, Ruan W, Sharp J, Sun Y, Thamo E, Wu M, Yi X (2020) A survey of safety and trustworthiness of deep neural networks: verification, testing, adversarial attack and defence, and interpretability. Comput Sci Rev 37:100270
Huang X, Kwiatkowska M, Wang S, Wu M (2017) Safety verification of deep neural networks. In: Computer aided verification: 29th international conference, CAV 2017, Heidelberg, Germany, July 24-28, 2017, Proceedings, Part I 30, pp 3–29. Springer
Katz G, Barrett C, Dill DL, Julian K, Kochenderfer MJ (2017) Reluplex: an efficient SMT solver for verifying deep neural networks. In: International conference on computer aided verification, pp 97–117. Springer
Katz G, Huang DA, Ibeling D, Julian K, Lazarus C, Lim R, Shah P, Thakoor S, Wu H, Al Z, Dill DL, Kochenderfer MJ, Barrett C (2019) The marabou framework for verification and analysis of deep neural networks. In: Dillig I, Serdar T (eds) Comput Aided Verif. Springer, Cham, pp 443–452
Khachiyan LG (1979), A polynomial time algorithm for linear programming. Doklady Akademii Nauk SSSR, 244(5), 1093–1096, English translation in Soviet Math. Dokl. 20:191–194
Klee F, Minty GJ (1972) How good is the simplex algorithm? Inequalities III:159–175
Kuutti S, Bowden R, Jin Y, Barber P, Fallah S (2020) A survey of deep learning applications to autonomous vehicle control. IEEE Trans Intell Transp Syst 22(2):712–733
Lahiri SK, Musuvathi M (2005) An efficient decision procedure for UTVPI constraints. In: Gramlich B (ed) Frontiers of combining systems. Springer, Berlin, pp 168–183
Liu C, Arnon T, Lazarus C, Barrett C, Kochenderfer MJ (2019). Algorithms for verifying deep neural networks. arXiv:1903.06758
Manzanas Lopez D, Johnson T, Tran H-D, Bak S, Chen X, Hobbs KL (2021) Verification of neural network compression of ACAS Xu lookup tables with star set reachability. In: AIAA Scitech 2021 Forum, p 0995
Miné A (2006) The octagon abstract domain. Higher-order Symb Comput 19(1):31–100
Orlin JB (1996) A polynomial time primal network simplex algorithm for minimum cost flows. In: Proceedings of the 7th annual ACM-SIAM symposium on discrete algorithms, SODA ’96, 474-481, USA. Society for Industrial and Applied Mathematics
Singh G, Gehr T, Mirman M, Püschel M, Vechev MT (2018) Fast and effective robustness certification. NeurIPS 1(4):6
Singh G, Gehr T, Püschel M, Vechev M (2019) An abstract domain for certifying neural networks. Proc ACM Program Lang 3(POPL):1–30
Sutton RS, Barto AG (2018) Reinforcement learning: an introduction, 2nd edn. MIT Press, Cambridge
Tjeng V, Xiao KY, Tedrake R (2018) Evaluating robustness of neural networks with mixed integer programming. In: International conference on learning representations
Tran H-D, Bak S, Xiang W, Johnson TT (2020). Verification of deep convolutional neural networks using imagestars. In: International conference on computer aided verification, pp 18–42. Springer
Tran H-D, Cai F, Diego ML, Musau P, Johnson TT, Koutsoukos X (2019) Safety verification of cyber-physical systems with reinforcement learning control. ACM Trans Embed Comput Syst (TECS) 18(5s):1–22
Tran H-D, Manzanas Lopez D, Musau P, Yang X, Nguyen LV, Xiang W, Johnson TT (2019) Star-based reachability analysis of deep neural networks. In: ter Beek MH, McIver A, Oliveira JN (eds) Formal methods—the next 30 years. Springer, Cham, pp 670–686
Tran H-D, Pal N, Musau P, Lopez DM, Hamilton N, Yang X, Bak S, Johnson TT (2021) Robustness verification of semantic segmentation neural networks using relaxed reachability. In: International conference on computer aided verification, pp 263–286. Springer
Tran H-D, Yang X, Lopez DM, Musau P, Nguyen LV, Xiang W, Bak S, Johnson TT (2020) NNV: the neural network verification tool for deep neural networks and learning-enabled cyber-physical systems. In: International conference on computer aided verification, pp 3–17. Springer
Wang S, Pei K, Whitehouse J, Yang J, Jana S (2018) Efficient formal safety analysis of neural networks. In: Advances in neural information processing systems, vol 31
Wang S, Zhang H, Xu K, Lin X, Jana S, Hsieh C-J, Kolter JZ (2021) Beta-crown: efficient bound propagation with per-neuron split constraints for complete and incomplete neural network verification. arXiv:2103.06624
Acknowledgement
This material is based upon work supported by the Air Force Office of Scientific Research and the Office of Naval Research under award numbers FA9550-19-1-0288, FA9550-21-1-0121, FA9550-22-1-0450, FA9550-22-1-0029, N00014-22-1-2156, and FA9550-23-1-0066. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the United States Air Force or the United States Navy. This research was supported in part by the Air Force Research Laboratory Information Directorate through the Air Force Office of Scientific Research Summer Faculty Fellowship Program, contract numbers FA8750-15-3-6003, FA9550-15-0001, and FA9550-20-F-0005. This work is also supported by the National Science Foundation (NSF) grant CCF-2009022 and by NSF CAREER awards CCF-2146563 and CNF-2237229.
Author information
Authors and Affiliations
Contributions
All authors contributed equally.
Corresponding author
Ethics declarations
Conflict of interest
We declare that we have no Conflict of interest.
Ethical approval
This manuscript was created by following all the ethical guidelines. In particular, an extended abstract of this work was published in FM 2023. This has been indicated in the abstract as a footnote.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Bak, S., Dohmen, T., Subramani, K. et al. The hexatope and octatope abstract domains for neural network verification. Form Methods Syst Des 64, 178–199 (2024). https://doi.org/10.1007/s10703-024-00457-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10703-024-00457-y