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Breaking the 1/√n Barrier: Faster Rates for Permutation-based Models in Polynomial Time
Proceedings of the 31st Conference On Learning Theory, PMLR 75:2037-2042, 2018.
Abstract
Many applications, including rank aggregation and crowd-labeling, can be modeled in terms of a bivariate isotonic matrix with unknown permutations acting on its rows and columns. We consider the problem of estimating such a matrix based on noisy observations of a subset of its entries, and design and analyze a polynomial-time algorithm that improves upon the state of the art. In particular, our results imply that any such n×n matrix can be estimated efficiently in the normalized Frobenius norm at rate ˜O(n−3/4), thus narrowing the gap between ˜O(n−1) and ˜O(n−1/2), which were hitherto the rates of the most statistically and computationally efficient methods, respectively.