arXiv:2505.05813cs.LG2025-05ICML被引 8

对比交叉熵与二元交叉熵在特征学习中的表现,发现两者都能实现类内紧凑、类间分离。

BCE vs. CE in Deep Feature Learning

  • BCE通过绝对决策分数调整,显式增强特征性质。
  • 实验表明BCE能提升分类性能和特征紧凑性与区分度。
  • 适合关注训练机制与特征分布的研究者参考。

在分类模型训练中,期望学习到的特征在类内紧凑且类间分离。作为主流损失函数,最小化交叉熵(CE)可最大化紧凑性与区分度,即达到神经坍缩(NC)。近期研究发现二元交叉熵(BCE)在多分类任务中也表现良好。本文首次证明,当达到最小值时,BCE同样能最大化类内紧凑性和类间区分度,即导致神经坍缩。我们指出,CE通过衡量决策分数的相对值,在逐样本分类中隐式增强特征属性;而BCE则基于决策分数的绝对值,将正负样本的决策分数统一调整至高/低水平。此外,BCE中的分类器偏置对决策分数形成显著约束,显式促进特征性质优化。实验结果与上述分析一致,表明BCE可提升分类效果,并带来更优的特征紧凑性与区分度。代码将公开。

原文摘要 · Abstract (English)

When training classification models, it expects that the learned features are compact within classes, and can well separate different classes. As the dominant loss function for training classification models, minimizing cross-entropy (CE) loss maximizes the compactness and distinctiveness, i.e., reaching neural collapse (NC). The recent works show that binary CE (BCE) performs also well in multi-class tasks. In this paper, we compare BCE and CE in deep feature learning. For the first time, we prove that BCE can also maximize the intra-class compactness and inter-class distinctiveness when reaching its minimum, i.e., leading to NC. We point out that CE measures the relative values of decision scores in the model training, implicitly enhancing the feature properties by classifying samples one-by-one. In contrast, BCE measures the absolute values of decision scores and adjust the positive/negative decision scores across all samples to uniformly high/low levels. Meanwhile, the classifier biases in BCE present a substantial constraint on the decision scores to explicitly enhance the feature properties in the training. The experimental results are aligned with above analysis, and show that BCE could improve the classification and leads to better compactness and distinctiveness among sample features. The codes will be released.

特征学习损失函数神经坍缩

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