Self-supervised learning (SSL) is a machine learning approach where the data itself provides supervision, eliminating the need for external labels. The model is forced to learn about the data structure or context by solving a pretext task. With SSL, models can learn from abundant and cheap unlabeled data, significantly reducing the cost of training models where labels are expensive or inaccessible.In Computer Vision, SSL is widely used as pre-training followed by a downstream task, such as supervised transfer, few-shot learning on smaller labeled data sets, and/or unsupervised clustering. Unfortunately, it is infeasible to evaluate SSL methods on all possible downstream tasks and objectively measure the quality of the learned representation. Instead, SSL methods are evaluated using in-domain evaluation protocols, such as fine-tuning, linear probing, and k-nearest neighbors (kNN). However, it is not well understood how well these evaluation protocols estimate the representation quality of a pre-trained model for different downstream tasks under different conditions, such as dataset, metric, and model architecture. We study how classification-based evaluation protocols for SSL correlate and how well they predict downstream performance on different dataset types. Our study includes eleven common image datasets and 26 models that were pre-trained with different SSL methods or have different model backbones. We find that in-domain linear/kNN probing protocols are, on average, the best general predictors for out-of-domain performance. We further investigate the importance of batch normalization and evaluate how robust correlations are for different kinds of dataset domain shifts. We challenge assumptions about the relationship between discriminative and generative self-supervised methods, finding that most of their performance differences can be explained by changes to model backbones.

自我监督学习方法是一种机器学习方法，通过解决预设任务，通过数据本身提供监督，从而避免了对外部标签的需求，并能够有效利用大量廉价无标签数据进行模型训练，从而显著降低了昂贵或无法获取标签的模型训练成本。本研究主要针对自我监督学习方法中的评估协议进行研究，评估表征质量，并预测不同类型数据集上不同下游任务的性能表现，发现基于领域内的线性/kNN探测协议是最好的普适性预测器，进一步研究了批归一化的重要性以及对不同类型数据集领域转移的鲁棒性的评估，同时对区分性和生成性自我监督方法之间的关系进行了挑战，并发现它们之间的性能差异大部分可以通过模型的改变来解释。

深入研究基于自监督预训练的图像分类性能评估