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Mixture of Noise for Pre-Trained Model-Based Class-Incremental Learning
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Proposes Mixture of Noise (Min), which learns task-specific positive-incentive noise generators inserted between ViT blocks and mixes them with learnable weights for exemplar-free pre-trained-model class-incremental learning.
Problem
Class-incremental learning with pre-trained models suffers from parameter drift that degrades the backbone's generalization; the paper asks whether beneficial (positive-incentive) noise can counter this while keeping the backbone frozen.
Approach
Model parameter drift as harmful noise and learn task-specific positive-incentive noise generators (Pi-Noise layers between transformer blocks) on top of an analytic classifier, then mix the noises with weights set by task-prototype similarity and refined through an auxiliary classifier, so a single backbone pass suffices at inference.
Key results
- On CIFAR-100 with ViT-B/16-IN21K at 50 steps, Min reaches 93.63% average and 89.82% last accuracy, versus the runner-up at 92.36%/87.39%.
- On ImageNet-A with ViT-B/16-IN21K, Min improves last-task accuracy by roughly 6-9 points over the runner-up across settings, per the paper's text.
- Ablation on the 10-step setting shows the noise expansion and noise mixture components each contribute; MIN achieves 92.12% last accuracy on CIFAR-100 versus 86.82% for the analytic baseline.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · CIFAR-100, 50 steps | average accuracy: 92.36 {${\pm 0.04}$} -> 93.63 {${\pm 0.20}$} | Helped |
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · CUB-200, 50 steps | average accuracy: 91.99 {${\pm 0.12}$} -> 93.21 {${\pm 0.14}$} | Helped |
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · ImageNet-A, 50 steps | average accuracy: 63.72 {${\pm 0.65}$} -> 66.15 {${\pm 0.35}$} | Helped |
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · ImageNet-R, 50 steps | average accuracy: 79.35 {${\pm 0.31}$} -> 82.26 {${\pm 0.16}$} | Helped |
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · FOOD-101, 50 steps | average accuracy: 91.57 {${\pm 0.10}$} -> 93.60 {${\pm 0.07}$} | Helped |
| Add MiN's task-specific noise generation and adaptive noise mixture | Analytic classifier with ViT-B/16-IN21K · Omnibenchmark, 50 steps | average accuracy: 85.06 {${\pm 0.12}$} -> 87.58 {${\pm 0.15}$} | Helped |
| Add task-specific noise generation and noise mixing (ablation) | Analytic classifier with ViT-B/16-IN21K · CIFAR-100, 10 steps | average accuracy: 91.18 {${\pm 0.03}$} -> 95.12 {${\pm 0.05}$} | Helped |
| Use only mean components of task noise (ablation) | MiN · CIFAR-100, 10 steps | average accuracy: 95.12 {${\pm 0.05}$} -> 89.27 {${\pm 0.24}$} | Hurt |
| Use only variance components of task noise (ablation) | MiN · CIFAR-100, 10 steps | average accuracy: 95.12 {${\pm 0.05}$} -> 94.37 {${\pm 0.05}$} | Hurt |
| Use only the last task's noise (ablation) | MiN · CIFAR-100, 10 steps | average accuracy: 95.12 {${\pm 0.05}$} -> 92.36 {${\pm 0.18}$} | Hurt |
| Use noise from a random task (ablation) | MiN · CIFAR-100, 10 steps | average accuracy: 95.12 {${\pm 0.05}$} -> 92.65 {${\pm 0.21}$} | Hurt |
Surprising findings
- Injecting learned noise into intermediate features, which is usually considered harmful, improves class-incremental accuracy, supporting the claim that some noise is beneficial.
Limitations
- Depends on a strong pre-trained feature extractor to guide the Pi-Noise generators.
- Adds extra down/up projection parameters (about 4% of ViT-B/16) in each Pi-Noise layer, though the trainable count is small.
Experimental setup
Datasets: CIFAR-100 CUB-200 ImageNet-A ImageNet-R FOOD-101 Omnibenchmark
Benchmarks: CIFAR-100 CUB-200 ImageNet-A ImageNet-R FOOD-101 Omnibenchmark
Metrics: average incremental accuracy last-task accuracy
Baselines: L2P DualPrompt CODA-Prompt SLCA FeCAM RanPAC APER EASE COFiMA MOS ACIL
Builds on: ACIL Positive-incentive noise L2P SLCA
Closest papers by meaning
- Navigating Semantic Drift in Task-Agnostic Class-Incremental Learning (ICML 2025 · similarity 0.87)
- Compress to One Point: Neural Collapse for Pre-Trained Model-Based Class-Incremental Learning (AAAI 2025 · similarity 0.87)
- Knowledge Memorization and Rumination for Pre-trained Model-based Class-Incremental Learning (CVPR 2025 · similarity 0.86)
- Prediction Error-based Classification for Class-Incremental Learning (ICLR 2024 · similarity 0.86)
- Task-recency bias strikes back: Adapting covariances in Exemplar-Free Class Incremental Learning (NeurIPS 2024 · similarity 0.86)
- Long-Tail Class Incremental Learning via Independent Sub-prototype Construction (CVPR 2024 · similarity 0.85)
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