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Tilt and Average : Geometric Adjustment of the Last Layer for Recalibration
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Proposes Tilt and Average (TNA), which recalibrates a trained classifier by randomly rotating the last-layer class vectors to a target mean angle (mRC) and averaging rotations, combinable with calibration-map methods.
Problem
Neural network classifiers are overconfident; post-hoc recalibration usually fits a calibration map on logits, while the geometry of the final linear layer is left unexploited.
Approach
Instead of fitting a calibration map, rotate the class weight vectors of the last linear layer by a controlled angle (Givens-rotation compositions, with mean rotation over classes mRC as the intensity), then average multiple tilted weights to recover accuracy; this relaxes confidence and is orthogonal to calibration-map methods.
Key results
- On CIFAR100-WideResNet28x10, None+TNA reduces ECE from 5.91% to 4.11% with accuracy change under 0.3%.
- On ImageNet-ViT-H/14, TNA(comp.) with ETS reduces ECE from 0.63% to 0.60%, and on ImageNet-ResNet50 TS+TNA(comp.) reduces ECE from 2.09% to 1.93%.
- TNA combined with calibration-map methods improves ECE over the calibration map alone in most dataset-model settings.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Apply TNA to the final-layer weights | Uncalibrated classifier · CIFAR10, WideResNet28x10 | ECE (%): 1.66_{.1} -> 0.66_{.14} | Helped |
| Apply TNA to the final-layer weights | Uncalibrated classifier · CIFAR100, MobileNetV2 | ECE (%): 10.03_{.19} -> 1.54_{.09} | Helped |
| Apply TNA to the final-layer weights | Uncalibrated classifier · ImageNet-1k, ResNet50 | ECE (%): 3.83_{.09} -> 1.73_{.06} | Helped |
| Add TNA to Temperature Scaling | Temperature Scaling · CIFAR10, WideResNet28x10 | ECE (%): 0.84_{.05} -> 0.78_{.13} | Helped |
| Add TNA to Temperature Scaling | Temperature Scaling · CIFAR100, MobileNetV2 | ECE (%): 1.82_{.33} -> 1.41_{.15} | Helped |
| Add TNA to Temperature Scaling | Temperature Scaling · ImageNet-1k, ResNet50 | ECE (%): 2.09_{.3} -> 2.02_{.27} | Helped |
| Reduce the penultimate-feature dimension from 640 to 10 (ablation) | TNA with WideResNet28x10 · CIFAR100 | ECE (%): 4.11 -> 11.04 | Hurt |
| Reduce the penultimate-feature dimension from 640 to 10 (ablation) | TNA with WideResNet28x10 · CIFAR10 | ECE (%): 0.66 -> 1.48 | Hurt |
| Average multiple tilted weights (increase ensemble members) (ablation) | TNA · ImageNet-1k, ResNet50 | accuracy | Helped |
| Use lower penultimate-feature dimension (ablation) | TNA · CIFAR10, WideResNet28x10 | accuracy | Hurt |
Surprising findings
- Applying TNA alone (no calibration map) outperforms temperature scaling on several settings, e.g., CIFAR10-WideResNet28x10 ECE 0.66% vs TS 0.84%.
Limitations
- Accuracy degrades as the rotation angle grows, requiring averaging to compensate; the theory relies on assumptions like equal class-wise angle changes and high dimensionality.
- Effectiveness diminishes when the penultimate feature dimension is small, as shown by ablation.
- Theoretical results rely on assumptions that are only partially validated experimentally.
Experimental setup
Datasets: CIFAR10 CIFAR100 SVHN ImageNet-1k
Benchmarks: CIFAR10 CIFAR100 SVHN ImageNet-1k
Metrics: accuracy ECE AdaECE
Baselines: Temperature Scaling IROvA Ensemble Temperature Scaling Atypicality-Aware Recalibration
Builds on: temperature scaling Givens rotation IROvA Ensemble Temperature Scaling Atypicality-Aware Recalibration
Closest papers by meaning
- Balancing Two Classifiers via A Simplex ETF Structure for Model Calibration (CVPR 2025 · similarity 0.85)
- Calibration Bottleneck: Over-compressed Representations are Less Calibratable (ICML 2024 · similarity 0.85)
- Improving Multi-Class Calibration through Normalization-Aware Isotonic Techniques (ICML 2025 · similarity 0.85)
- Confidence Calibration of Classifiers with Many Classes (NeurIPS 2024 · similarity 0.84)
- Optimal and Provable Calibration in High-Dimensional Binary Classification: Angular Calibration and Platt Scaling (NeurIPS 2025 · similarity 0.84)
- Reassessing How to Compare and Improve the Calibration of Machine Learning Models (ICLR 2025 · similarity 0.84)
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