论文标题

带有内存的梯度方法,以最大程度地减少复合功能

Gradient Methods with Memory for Minimizing Composite Functions

论文作者

Florea, Mihai I.

论文摘要

最近引入的带有内存的梯度方法使用过去的Oracle信息的子集创建目标函数的准确模型,从而使他们能够超越实际性能中的梯度方法。该模型引入了一个开销,除了平稳的无约束问题外,所有问题都很重要。在这项工作中,我们介绍了几种具有内存的梯度方法,可以有效地解决复合问题,包括无影响的问题。每次迭代中的辅助问题仍然无法准确解决,但是我们展示了如何更改模型以及如何初始化辅助问题求解器,以确保这种不精确度不会降低收敛保证。此外,我们会动态地增加融合保证,以超越其无记忆的同行。应用加速度时保留了这些特性,并且不符合性的遏制进一步阻止了误差累积。我们的方法能够估算关键的几何参数,以在许多重要的复合问题子类上达到最新的最差案例,因为客观平滑部分满足了强大的凸状态或其放松。特别是,我们制定了一种适用于具有均方根收敛的优化方法的近乎最佳的重新启动策略。我们通过模拟支持理论结果。

The recently introduced Gradient Methods with Memory use a subset of the past oracle information to create an accurate model of the objective function that enables them to surpass the Gradient Method in practical performance. The model introduces an overhead that is substantial on all problems but the smooth unconstrained ones. In this work, we introduce several Gradient Methods with Memory that can solve composite problems efficiently, including unconstrained problems with non-smooth objectives. The auxiliary problem at each iteration still cannot be solved exactly but we show how to alter the model and how to initialize the auxiliary problem solver to ensure that this inexactness does not degrade the convergence guarantees. Moreover, we dynamically increase the convergence guarantees as to provably surpass those of their memory-less counterparts. These properties are preserved when applying acceleration and the containment of inexactness further prevents error accumulation. Our methods are able to estimate key geometry parameters to attain state-of-the-art worst-case rates on many important subclasses of composite problems, where the objective smooth part satisfies a strong convexity condition or a relaxation thereof. In particular, we formulate a near-optimal restart strategy applicable to optimization methods with sublinear convergence guarantees of any order. We support the theoretical results with simulations.

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