将检查点更新概率与动量参数联系起来在单循环方差减少方法中
Relating Checkpoint Update Probabilities to Momentum Parameters in Single-Loop Variance Reduction Methods
AI总结:
本文提出了一种单循环方差减少方法,通过将检查点更新概率与动量参数联系起来,实现加速与方差减少的平衡,从而在标准假设下达到近最优复杂性。
摘要:
我们提出了一种单循环方差减少加速框架,该框架将检查点更新概率与动量参数联系起来,用于解决具有光滑部分的复合一般凸问题,其中光滑部分具有有限和结构。在所提出的框架下,动量参数的增长率进一步被改变,从而创建了一个新的连续权衡,即在加速和方差减少之间,由关键参数α∈[0,1]控制。获得了一系列新的复杂性,并在统一框架下重新发现了某些已知方法的复杂性。当由于问题的规模庞大或计算资源不足而限制小批量大小时,通过选择合适的α,可以为任何预设的精度目标实现近最优复杂性。分析显示,尽管考虑的梯度Oracle是精确的,但加速伴随着隐含的方差减少代价,因此获得的最优α不一定对应于最大的允许加速强度。在不预设目标精度的情况下,所提出的方法在标准假设下(n是有限和的组件数)能够达到近最优复杂性~O(n+√n/√ε),以获得ε精度的解,显著优于之前单循环方差减少方法的最佳复杂性O(n+n/√ε),后者不超过确定性方法FISTA的复杂性。数值实验展示了所提出方法的效率,并验证了其他理论发现。
英文摘要:
We propose a single-loop variance-reduced acceleration framework, which relates checkpoint update probabilities to momentum parameters, for solving the composite general convex problem where the smooth part has the finite-sum structure. Under the proposed framework, the growth rate of the momentum parameter is further altered, creating a novel continuous trade-off between acceleration and variance reduction, controlled by the key parameter $α\in [0,1]$. A series of novel complexity is obtained, and some complexity of distinct known methods are rediscovered under the unified framework. When the mini-batch size is restricted due to the massive scale of the problem or the computational resource shortage, near-optimal complexity can still be achieved by choosing suitable $α$ for any prefixed target accuracy. Analysis shows that although the considered gradient oracle is exact, acceleration comes with implicit price of heavier variance reduction, hence the obtained optimal $α$ not necessarily corresponds to the largest allowable acceleration strength. Without prefixing the target accuracy, the proposed method achieves the near-optimal complexity $\tilde{\mathcal{O}}(n+\sqrt{n}/\sqrtε)$ to obtain an $ε$-accurate solution under standard assumptions ($n$ is the number of components of the finite-sum), significantly improves upon previous best complexity $\mathcal{O}(n+n/\sqrtε)$ of single-loop variance reduction methods, which does not exceed the complexity of the deterministic method FISTA. Numerical experiments demonstrate the efficiency of the proposed method and validate other theoretical findings.
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