We improve the understanding of the $\textit{golden ratio algorithm}$, which solves monotone variational inequalities (VI) and convex-concave min-max problems via the distinctive feature of adapting the step sizes to the local Lipschitz constants. Adaptive step sizes not only eliminate the need to pick hyperparameters, but they also remove the necessity of global Lipschitz continuity and can increase from one iteration to the next. We first establish the equivalence of this algorithm with popular VI methods such as reflected gradient, Popov or optimistic gradient descent-ascent in the unconstrained case with constant step sizes. We then move on to the constrained setting and introduce a new analysis that allows to use larger step sizes, to complete the bridge between the golden ratio algorithm and the existing algorithms in the literature. Doing so, we actually eliminate the link between the golden ratio $\frac{1+\sqrt{5}}{2}$ and the algorithm. Moreover, we improve the adaptive version of the algorithm, first by removing the maximum step size hyperparameter (an artifact from the analysis) to improve the complexity bound, and second by adjusting it to nonmonotone problems with weak Minty solutions, with superior empirical performance.
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我们提出了随机方差降低算法,以求解凸 - 凸座鞍点问题,单调变异不平等和单调夹杂物。我们的框架适用于Euclidean和Bregman设置中的外部,前向前后和前反向回复的方法。所有提出的方法都在与确定性的对应物相同的环境中收敛,并且它们要么匹配或改善了解决结构化的最低最大问题的最著名复杂性。我们的结果加强了变异不平等和最小化之间的差异之间的对应关系。我们还通过对矩阵游戏的数值评估来说明方法的改进。
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Unusually, intensive heavy rain hit the central region of Korea on August 8, 2022. Many low-lying areas were submerged, so traffic and life were severely paralyzed. It was the critical damage caused by torrential rain for just a few hours. This event reminded us of the need for a more reliable regional precipitation nowcasting method. In this paper, we bring cycle-consistent adversarial networks (CycleGAN) into the time-series domain and extend it to propose a reliable model for regional precipitation nowcasting. The proposed model generates composite hybrid surface rainfall (HSR) data after 10 minutes from the present time. Also, the proposed model provides a reliable prediction of up to 2 hours with a gradual extension of the training time steps. Unlike the existing complex nowcasting methods, the proposed model does not use recurrent neural networks (RNNs) and secures temporal causality via sequential training in the cycle. Our precipitation nowcasting method outperforms convolutional long short-term memory (ConvLSTM) based on RNNs. Additionally, we demonstrate the superiority of our approach by qualitative and quantitative comparisons against MAPLE, the McGill algorithm for precipitation nowcasting by lagrangian extrapolation, one of the real quantitative precipitation forecast (QPF) models.
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大脑中的功能连接通常由加权网络表示,其中节点表示大脑中的位置,并且边缘表示这些位置之间的连接强度。分析这些数据的一个挑战是各个边缘水平的推断并不是特别生物学上的意义;解释在所谓的功能区域或节点组和它们之间的连接级别更有用;这通常被称为神经影像学文献中的“图表感知”推断。然而,汇集功能区域导致信息损失和更低的准确性。另一个挑战是主题内的边缘权重之间的相关性,这使得基于独立假设不可靠的推断。我们通过线性混合效果模型来解决这两种挑战,该挑战涉及功能区域和边缘依赖性,同时仍然建模各个边缘权重,以避免丢失信息。该模型允许将两种群体(例如患者和健康对照)进行比较,无论是在功能区水平和各个边缘水平,都导致生物学上有意义的解释。我们将该模型符合精神分裂症和健康控制的休息状态FMRI数据,获得与精神分裂症文献一致的可解释结果。
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