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arXiv 2008.03703cs.LGstat.ML
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神经网络实现了什么以及为什么:通过影响估计发现长尾

What Neural Networks Memorize and Why: Discovering the Long Tail via Influence Estimation

Apple(苹果公司);Google Research, Brain Team(谷歌研究院 Brain 团队)

Vitaly Feldman, Chiyuan Zhang

摘要:

众所周知,深度学习算法具有非常好地拟合训练数据的倾向,并且通常甚至拟合离群值和错误标记的数据点。这种拟合需要记住训练数据标签,这一现象已经引起了重大的研究兴趣,但迄今为止还没有给出令人信服的解释。Feldman(2019)最近的一项工作基于两种见解的结合提出了对这一现象的理论解释。首先,自然图像和数据分布(非正式地)已知是长尾的,即具有显著比例的罕见和非典型示例。第二,在一个简单的理论模型中,当数据分布是长尾时,这种记忆对于实现接近最优的泛化误差是必要的。然而,没有为这一解释提供直接的经验证据,甚至也没有提供获得这种证据的方法。在这项工作中,我们设计实验来测试这个理论中的关键思想。实验需要估计每个训练样本对每个测试样本的准确度的影响以及训练样本的记忆值。直接估计这些数量是计算禁止,但我们表明,密切相关的子采样的影响和记忆值可以更有效地估计。我们的实验证明了记忆泛化的几个标准基准的显着好处。它们还为(Feldman,2019)中提出的理论提供了定量和视觉上令人信服的证据。

英文摘要:

Deep learning algorithms are well-known to have a propensity for fitting the training data very well and often fit even outliers and mislabeled data points. Such fitting requires memorization of training data labels, a phenomenon that has attracted significant research interest but has not been given a compelling explanation so far. A recent work of Feldman (2019) proposes a theoretical explanation for this phenomenon based on a combination of two insights. First, natural image and data distributions are (informally) known to be long-tailed, that is have a significant fraction of rare and atypical examples. Second, in a simple theoretical model such memorization is necessary for achieving close-to-optimal generalization error when the data distribution is long-tailed. However, no direct empirical evidence for this explanation or even an approach for obtaining such evidence were given. In this work we design experiments to test the key ideas in this theory. The experiments require estimation of the influence of each training example on the accuracy at each test example as well as memorization values of training examples. Estimating these quantities directly is computationally prohibitive but we show that closely-related subsampled influence and memorization values can be estimated much more efficiently. Our experiments demonstrate the significant benefits of memorization for generalization on several standard benchmarks. They also provide quantitative and visually compelling evidence for the theory put forth in (Feldman, 2019).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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