Near-Optimal Degree Testing for Bayes Nets

Abstract: This paper considers the problem of testing the maximum in-degree of the Bayes net underlying an unknown probability distribution $P$ over ${0,1}^n$, given sample access to $P$. We show that the sample complexity of the problem is $\tilde{\Theta}(2^{n/2}/\varepsilon^2)$. Our algorithm relies on a testing-by-learning framework, previously used to obtain sample-optimal testers; in order to apply this framework, we develop new algorithms for ``near-proper'' learning of Bayes nets, and high-probability learning under $\chi^2$ divergence, which are of independent interest.