论文标题
小小的椭圆形方法
Ellipsoid method for convex stochastic optimization in small dimension
论文作者
论文摘要
本文认为凸功能的期望最小化。这种类型的问题通常在机器学习和许多其他应用程序中出现。实际上,随机梯度下降(SGD)和类似的程序通常用于解决此类问题。我们建议将椭圆形方法与Minibatching一起使用,该方法线性收敛,因此需要比SGD的迭代率要少得多。我们的实验证实了这一点,这些实验已公开可用。该算法不需要平滑度,也不需要目标函数的强凸度来实现线性收敛。我们证明,当使用与所需的精度为-2的小型尺寸时,该方法具有近似溶液的近似解决方案。这使算法有效地并行执行,而SGD批处理并行化的可能性相当有限。尽管快速收敛,但椭圆形方法可能会导致对Oracle的总呼叫总数比SGD的总数更大,SGD可以与小批量相吻合。复杂性在问题的维度上是二次的,因此该方法适用于相对较小的维度。
The article considers minimization of the expectation of convex function. Problems of this type often arise in machine learning and a number of other applications. In practice, stochastic gradient descent (SGD) and similar procedures are often used to solve such problems. We propose to use the ellipsoid method with minibatching, which converges linearly and hence requires significantly less iterations than SGD. This is verified by our experiments, which are publicly available. The algorithm does not require neither smoothness nor strong convexity of target function to achieve linear convergence. We prove that the method arrives at approximate solution with given probability when using minibatches of size proportional to the desired precision to the power -2. This enables efficient parallel execution of the algorithm, whereas possibilities for batch parallelization of SGD are rather limited. Despite fast convergence, ellipsoid method can result in a greater total number of calls to oracle than SGD, which works decently with small batches. Complexity is quadratic in dimension of the problem, hence the method is suitable for relatively small dimensionalities.