Organizations: School of Computer Science and Software Engineering, Shenzhen University, Shenzhen, China · Computer Vision Institute, School of Artificial Intelligence, Shenzhen University, Shenzhen, China · School of Engineering, Huaqiao University, Quanzhou, China · Guangdong Provincial Key Laboratory of Intelligent Information Processing, Shenzhen University, Shenzhen, China
Contrastive learning has achieved remarkable success in self-supervised representation learning, often guided by information-theoretic objectives such as mutual information maximization. Motivated by the limitations of static augmentations and rigid invariance constraints, we propose IE-CL (Incremental-Entropy Contrastive Learning), a framework that explicitly optimizes the entropy gain between augmented views while preserving semantic consistency. Our theoretical framework reframes the challenge by identifying the encoder as an information bottleneck and proposes a joint optimization of two components: a learnable transformation for entropy generation and an encoder regularizer for its preservation. Experiments on CIFAR-10/100, STL-10, and ImageNet demonstrate that IE-CL consistently improves performance under small-batch settings. Moreover, our core modules can be seamlessly integrated into existing frameworks. This work bridges theoretical principles and practice, offering a new perspective in contrastive learning.
Figures & tables
Figure 1: Overview of the proposed IE-CL. We define incremental entropy as the absolute change in entropy induced by classical contrastive augmentations (see Definition 3.2 ). To optimize the contrastive learning process, we propose the S ample A ugmentation I ncremental B lock ( SAIB ), a learnable module that ensures the local Jacobian determinant > 1. By incorporating sample-level incremental entropy into contrastive optimization, we establish a principled framework that improves the effectiveness of self-supervised representation learning.
Method
100 ep
200 ep
400 ep
800 ep
Batch Size
SimCLR (ICML’20) Chen et al. (2020a)
66.5
68.3
69.8
71.1
4096
SwAV (NeurIPS’20) Caron et al. (2020)
66.5
69.1
70.7
71.0
4096
MoCo-v2 (CVPR’20) Chen et al. (2020c)
67.4
69.9
70.9
71.3
256
SimSiam (ICCV’21) Chen and He (2021)
68.1
70.0
70.8
71.7
256
NNCLR (ICCV’21) Dwibedi et al. (2021)
65.4
66.1
66.8
68.7
1024
All4One (ICCV’23) Estepa et al. (2023)
65.4
66.0
66.6
68.9
1024
Table 1: The comparison of the proposed method with ResNet-50 as the backbone under different numbers of pre-training iterations. Using BOLD and Underline formatting to highlight the best and second results.
Table 2: Comparison of self-supervised learning methods on various datasets (left) and segmentation/detection performance on PASCAL VOC2012 (right).
Figure 4
Configuration
SAIB
KL Reg.
Encoder Reg.
Top-1
MoCo-v2 (Baseline)
✗
✗
✗
52.50
+ Entropy Generation
✓
✗
✗
58.80
+ Semantic Consistency
✓
✓
✗
59.15
IE-CL (Full Framework)
✓
✓
✓
59.41
Table 3: Ablation study of the IE-CL components on ImageNet-1k using MoCo-v2 with a ResNet-18 backbone. We incrementally add our proposed components: the SAIB module for entropy generation, KL regularization for semantic consistency, and an Encoder Regularizer (implemented via Spectral Normalization) for entropy preservation.
Table 6Figure 7
Appendix figures & tables3 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 6: Structure of Sample Augmentation Incremental Block ( SAIB ). Note that due to the patching of the 3-channel image, the batch occupies the position of the original channel. Therefore, it is possible to drive the inter-batch information to communicate by changing the original convolutional channels. All the convolutions in this block are cascaded with BN layers and Swish Ramachandran et al. (2017) to achieve nonlinear augmentation capability. And then convolved and non-linearly processed, and finally reconstructed back to the original position through positional coding.
Figure 7: Comparison of the time taken by different methods to train an epoch on ImageNet-1k with batch of 256. The proposed IE-CL, although it includes an additional non-isometric transform module SAIB, still spends less training cost compared to the previous methods because it uses momentum to update the Query encoder.
Figure 8: As a plug-and-play module, SAIB enhances the performance of existing contrastive learning methods with limited additional computational overhead. Overall, it achieves effective performance gains within an acceptable increase in training time—on average, approximately 8.8% more—compared to the original models (see Table 5 in the main text).
Contrastive learning trains representations by bringing related examples together and separating unrelated ones for recognition, retrieval, and transfer.
Contrastive self-supervised learning has achieved strong performance by learning representations from multiple augmented views of the same image. However, most existing methods construct positive pairs using independently sampled stochastic augmentations, which may alter semantic content and ignore the intrinsic geometry of the data distribution. In this work, we propose OTCLR, an optimal transport-aware framework for contrastive learning representations that generates geometry-consistent positive samples. Instead of directly contrasting two randomly augmented views, we construct intermediate views between the original image and its augmented variants through entropic optimal-transport displacement interpolation. These transport-interpolated samples serve as positive views that better preserve image structure while explicitly modeling spatial distributional geometry. To further promote smooth representation learning, we evaluate auxiliary Sinkhorn regularization terms that encourage transport-interpolated views to remain consistent with their endpoint images. The proposed method can be incorporated into standard contrastive learning pipelines without modifying the encoder architecture. Experiments on multiple benchmark datasets show that our approach improves representation quality and transfer learning performance compared with conventional augmentation-based contrastive learning baselines.
Akshit Nanda, Shahzad Ahmad, Ram Prasad Padhy
Department of Computer Science and Engineering, Indian Institute of Technology Bhubaneswar · Østfold University of Applied Sciences, NTNU
While Contrastive Learning (CL) has revolutionized self-supervised representation learning, its latent representations remain highly entangled and opaque, limiting their interpretability in safety-critical applications. We identify that a fundamental cause of this entanglement is the reliance on deterministic similarity measures, which treat all feature dimensions equally. In compositional scenes, this creates an Optimization Conflict: common background features, such as, "blue sky", are encouraged to align in positive pairs but simultaneously repelled in negative pairs, causing gradient oscillations that hinder precise semantic disentanglement. To address this, we propose BayesNCL (Bayesian Gated Non-Negative Contrastive Learning). Unlike standard approaches, BayesNCL introduces a probabilistic gating mechanism that dynamically filters out task-irrelevant, high-frequency common features while selectively retaining discriminative semantics. By formalizing feature selection as a variational inference problem with a sparse Bernoulli prior, our method effectively resolves the optimization conflict. Empirical experimental results on Imagenet-100 demonstrate that BayesNCL achieves a remarkable 142.1% improvement in semantic consistency compared to state-of-the-art baselines, yielding highly interpretable representations without compromising downstream task performance. Code is available at https://github.com/Cui-Peng-624/BayesNCL.
Peng Cui, Jiahao Zhang, Lijie Hu
Mohamed bin Zayed University of Artificial Intelligence (MBZUAI).
Contrastive learning has become a cornerstone of modern representation learning, allowing training with massive unlabeled data for both task-specific and general (foundation) models. A prototypical loss in contrastive training is InfoNCE and its variants. In this work, we show that the InfoNCE objective induces Gaussian structure in representations that emerge from contrastive training. We establish this result in two complementary regimes. First, we show that under certain alignment and concentration assumptions, projections of the high-dimensional representation asymptotically approach a multivariate Gaussian distribution. Next, under less strict assumptions, we show that adding a small asymptotically vanishing regularization term that promotes low feature norm and high feature entropy leads to similar asymptotic results. We support our analysis with experiments on synthetic and CIFAR-10 datasets across multiple encoder architectures and sizes, demonstrating consistent Gaussian behavior. This perspective provides a principled explanation for commonly observed Gaussianity in contrastive representations. The resulting Gaussian model enables principled analytical treatment of learned representations and is expected to support a wide range of applications in contrastive learning.