Learning One Convolutional Layer with Overlapping Patches
Proceedings of the 35th International Conference on Machine Learning, PMLR 80:1783-1791, 2018.
We give the first provably efficient algorithm for learning a one hidden layer convolutional network with respect to a general class of (potentially overlapping) patches under mild conditions on the underlying distribution. We prove that our framework captures commonly used schemes from computer vision, including one-dimensional and two-dimensional “patch and stride” convolutions. Our algorithm– Convotron– is inspired by recent work applying isotonic regression to learning neural networks. Convotron uses a simple, iterative update rule that is stochastic in nature and tolerant to noise (requires only that the conditional mean function is a one layer convolutional network, as opposed to the realizable setting). In contrast to gradient descent, Convotron requires no special initialization or learning-rate tuning to converge to the global optimum. We also point out that learning one hidden convolutional layer with respect to a Gaussian distribution and just one disjoint patch $P$ (the other patches may be arbitrary) is easy in the following sense: Convotron can efficiently recover the hidden weight vector by updating only in the direction of $P$.