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Title: Verification of Generative-Model-Based Visual Transformations

Paper content:
Generative networks are promising models for specifying visual transformations.
Unfortunately, certification of generative models is challenging as one needs to capture sufficient non-convexity so to produce precise bounds on the output.
Existing verification methods either fail to scale to generative networks or do not capture enough non-convexity.
In this work, we present a new verifier, called ApproxLine, that can certify non-trivial properties of generative networks.
ApproxLine performs both deterministic and probabilistic abstract interpretation and captures infinite sets of outputs of generative networks.
We show that ApproxLine can verify interesting interpolations in the network's latent space.
Neural networks are becoming increasingly used across a wide range of applications, including facial recognition and autonomous driving.
So far, certification of their behavior has remained predominantly focused on uniform classification of norm-bounded balls Katz et al., 2017; Wong et al., 2018; Gowal et al., 2018; Singh et al., 2018; Raghunathan et al., 2018; Tjeng et al., 2017; Dvijotham et al., 2018b; Salman et al., 2019; Dvijotham et al., 2018c; , which aim to capture invisible perturbations.
However, a system's safety can also depend on its behavior on visible transformations.
For these reasons, investigation of techniques to certify more complex specifications has started to take place (Liu et al., 2019; Dvijotham et al., 2018a; Singh et al., 2019) .
Of particular interest is the work of Sotoudeh & Thakur (2019) which shows that if the inputs of a network are restricted to a line segment, the verification problem can sometimes be efficiently solved exactly.
The resulting method has been used to certify non-norm-bounded properties of ACAS Xu networks (Julian et al., 2018) and improve Integrated Gradients (Sundararajan et al., 2017) .
This work We extend this technique in two key ways:
(i) we demonstrate how to soundly approximate EXACTLINE, handling significantly larger networks faster than even methods based on sampling can (a form of deterministic abstract interpretation), and
(ii) we use this approximation to provide guaranteed bounds on the probabilities of outputs given a distribution over the inputs (a form of probabilistic abstract interpretation).
We believe this is the first time probabilistic abstract interpretation has been applied in the context of neural networks.
Based on these techniques, we also provide the first system capable of certifying interesting properties of generative networks.
In this paper we presented a highly scalable non-convex relaxation to verify neural network properties where inputs are restricted to a line segment.
Our results show that our method is faster and more precise than previous methods for the same networks, including sampling.
This speed and precision permitted us to verify properties based on interesting visual transformations induced by generative networks for the first time, including probabilistic properties.

assistant: text: We verify deterministic and probabilistic properties of neural networks using non-convex relaxations over visible transformations specified by generative models