【论文阅读】Pseudo-Labeling and Confirmation Bias in Deep Semi-Supervised Learning

该论文探讨了在图像分类中的半监督学习方法,提出使用网络预测生成软伪标签来学习无标记数据。研究发现,简单的伪标签方法可能会因为确认偏差导致过拟合不正确的标签。为解决此问题,论文引入了MixUp增强和设置每个小批量的最小标记样本数作为有效的正则化技术,减少了确认偏差,并在CIFAR-10/100,SVHN和Mini-ImageNet等数据集上取得了最先进的结果,甚至优于一致性正则化方法。

论文下载
GitHub
bib:

@INPROCEEDINGS{
   
   ,
  title		= {
   
   Pseudo-Labeling and Confirmation Bias in Deep Semi-Supervised Learning},
  author	= {
   
   Eric Arazo and Diego Ortego and Paul Albert and Noel E O'Connor and Kevin McGuinness},
  booktitle	= {
   
   IJCNN},
  year		= {
   
   2020},
  pages     = {
   
   1--8}
}

1. 摘要

Semi-supervised learning, i.e. jointly learning from labeled and unlabeled samples, is an active research topic due to its key role on relaxing human supervision.

总览半监督学习。

In the context of image classification, recent advances to learn from unlabeled samples are mainly focused on consistency regularization methods that encourage invariant predictions for different perturbations of unlabeled samples.

提到半监督分类中的一致性正则。

We, conversely, propose to learn from unlabeled data by generating soft pseudo-labels using the network predictions.

提到本文中适用了伪标签技术(soft pseudo-labels)。

We show that a naive pseudo-labeling overfits to incorrect pseudo-labels due to the so-called confirmation bias and demonstrate that mixup augmentation and setting a minimum number of labeled samples per mini-batch are effective regularization techniques for reducing it.

核心的贡献。提出了确认偏差(confirmation bias),本文贡献是证明了mixup augmentationsetting a minimum number of labeled samples per mini-batch是有效减少确认偏差的正则技术。

The proposed approach achieves state-of-the-art results in CIFAR-10/100, SVHN, and Mini-ImageNet despite being much simpler than other methods.

These results demonstrate that pseudo-labeling alone can outperform consistency regularization methods, while the opposite was supposed in previous work.

这一点就很令人惊讶了,伪标签技术的方法超过了一致性正则的方法。还没看原文,应该是还没有出现FixMatchFlexMatch方法。

2. 算法描述

符号 意义
D l = { ( x i , y i ) } i = 1 N l D_l = \{(x_i, y_i)\}^{N_l}_{i=1} Dl={(xi,yi)}i=1Nl 有标记数据
D u = { x i } i = 1 N u D_u = \{x_i\}^{N_u}_{i=1} Du={ xi}i=1Nu 无标记数据
D ~ u = { ( x i , y ~ i } i = 1 N \widetilde{D}_u = \{(x_i, \widetilde{y}_i\}^{N}_{i=1} D u={(xi,y
仅给定的三条引用内容未涉及“基于原型的伪标签细化方法用于半监督高光谱图像分类”以及 “Prototype-based pseudo-label refinement for semi-supervised hyperspectral image classification” 的相关信息,无法依据这些引用准确回答。不过,一般而言,在半监督高光谱图像分类里,基于原型的伪标签细化方法会先利用少量有标签样本构建原型,这些原型代表不同的类别特征。接着,用这些原型为无标签样本生成伪标签。之后,通过一系列细化操作来提升伪标签的质量,例如考虑局部上下文信息、特征相似性等。 伪代码示例(仅为概念示意): ```python # 假设 hyperspectral_data 是高光谱图像数据, labeled_indices 是有标签样本的索引, labels 是对应标签 import numpy as np def prototype_based_pseudo_label_refinement(hyperspectral_data, labeled_indices, labels): # 构建原型 prototypes = [] unique_labels = np.unique(labels) for label in unique_labels: label_indices = np.where(labels == label)[0] prototype = np.mean(hyperspectral_data[labeled_indices[label_indices]], axis=0) prototypes.append(prototype) # 为无标签样本生成伪标签 unlabeled_indices = np.setdiff1d(np.arange(len(hyperspectral_data)), labeled_indices) pseudo_labels = [] for idx in unlabeled_indices: distances = [np.linalg.norm(hyperspectral_data[idx] - proto) for proto in prototypes] pseudo_label = np.argmin(distances) pseudo_labels.append(pseudo_label) # 伪标签细化(简单示例:基于局部上下文) refined_pseudo_labels = [] for i, idx in enumerate(unlabeled_indices): # 这里简单假设周围 3 个样本作为局部上下文 local_indices = get_local_indices(idx, hyperspectral_data.shape) local_pseudo_labels = [pseudo_labels[np.where(unlabeled_indices == local_idx)[0][0]] for local_idx in local_indices if local_idx in unlabeled_indices] if len(local_pseudo_labels) > 0: most_common_label = np.bincount(local_pseudo_labels).argmax() refined_pseudo_labels.append(most_common_label) else: refined_pseudo_labels.append(pseudo_labels[i]) return refined_pseudo_labels def get_local_indices(idx, shape): # 获取周围 3 个样本的索引 rows, cols = shape[:2] row, col = np.unravel_index(idx, (rows, cols)) local_indices = [] if row > 0: local_indices.append(np.ravel_multi_index((row - 1, col), (rows, cols))) if row < rows - 1: local_indices.append(np.ravel_multi_index((row + 1, col), (rows, cols))) if col > 0: local_indices.append(np.ravel_multi_index((row, col - 1), (rows, cols))) if col < cols - 1: local_indices.append(np.ravel_multi_index((row, col + 1), (rows, cols))) return local_indices ```
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