Stochastic Variance Reduced Gradient Methods Using a Trust-Region-Like Scheme

摘要

Stochastic variance reduced gradient (SVRG) methods are important approaches to minimize the average of a large number of cost functions frequently arising in machine learning and many other applications. In this paper, based on SVRG, we propose a SVRG-TR method which employs a trust-region-like scheme for selecting stepsizes. It is proved that the SVRG-TR method is linearly convergent in expectation for smooth strongly convex functions and enjoys a faster convergence rate than SVRG methods. In order to overcome the difficulty of tuning stepsizes by hand, we propose to combine the Barzilai-Borwein (BB) method to automatically compute stepsizes for the SVRG-TR method, named as the SVRG-TR-BB method. By incorporating mini-batching scheme with SVRG-TR and SVRG-TR-BB, respectively, we further propose two extended methods mSVRG-TR and mSVRG-TR-BB. Linear convergence and complexity of mSVRG-TR are given. Numerical experiments on some standard datasets show that SVRG-TR and SVRG-TR-BB are generally better than or comparable to SVRG with best-tuned stepsizes and some modern stochastic gradient methods, while mSVRG-TR and mSVRG-TR-BB are very competitive with mini-batch variants of recent successful stochastic gradient methods.