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A PID Controller Approach for Adaptive Probability-dependent Gradient Decay in Model Calibration
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Proposes PID-AGD, which uses a PID controller on a validation-set relative calibration error to adapt a probability-dependent gradient decay coefficient β in the softmax loss, plus a learning-rate compensation rule, to improve calibration without sacrificing accuracy.
Problem
Deep classifiers are overconfident, and calibration tends to overfit earlier than accuracy during cross-entropy training, so accuracy and calibration are not optimized consistently.
Approach
Treat the gradient decay coefficient β of a parametric softmax loss as a controlled variable, with validation-set relative calibration error (RCE) as the feedback signal for a PID controller that adjusts β each epoch; a derived learning-rate rule compensates for the resulting gradient-magnitude changes.
Key results
- On CIFAR-100 ResNet18, ECE drops to 0.006 for the proposed method versus 0.160 uncalibrated and 0.033 for temperature scaling (Table 1).
- On CIFAR-100 ResNet35 with the PID controller and gradient compensation, accuracy is 74.7% versus 73.8% for SGD softmax baseline, with ECE 0.012 versus 0.172 (Table 3).
- On 102 Flower ResNet50, ECE is 0.033 versus 0.075 for the next best method (TS-AvUC).
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| apply PID-based adaptive probability-dependent gradient decay | ResNet18 · CIFAR-10 | ECE: 0.041±0.010 -> 0.007±0.002 | Helped |
| apply PID-based adaptive probability-dependent gradient decay | ResNet35 · CIFAR-100 | accuracy: 73.8±0.30 -> 75.4±0.39 | Helped |
| apply PID-based adaptive probability-dependent gradient decay | ResNet35 · CIFAR-100 | ECE: 0.172±0.022 -> 0.011±0.003 | Helped |
| add gradient compensation to PID-controlled SGD (ablation) | ResNet35 · CIFAR-100 | accuracy: 72.5% -> 74.7% | Helped |
| add gradient compensation to PID-controlled SGD (ablation) | ResNet35 · CIFAR-100 | ECE: 0.022 -> 0.012 | Helped |
| replace SGD with Adam under PID control (ablation) | ResNet35 · CIFAR-100 | accuracy: 73.8% -> 63.5% | Hurt |
| increase gradient decay factor β from 0.1 to 20 (ablation) | ResNet34 · Tiny-ImageNet | ECE: 0.224 -> 0.015 | Helped |
| increase gradient decay factor β from 0.1 to 20 (ablation) | ResNet34 · Tiny-ImageNet | Top-1 Acc (%): 53.7 -> 52.8 | Mixed |
| increase gradient decay factor β from 0.01 to 20 (ablation) | ResNet50 · Tiny-ImageNet | ECE: 0.249 -> 0.045 | Helped |
| increase gradient decay factor β from 0.01 to 20 (ablation) | ResNet50 · Tiny-ImageNet | Top-1 Acc (%): 56.2 -> 55.9 | Mixed |
| vary PID controller P, I, and D settings (ablation) | ResNet35 · CIFAR-100 | accuracy | No clear effect |
| use excessively high PID parameter settings (ablation) | ResNet35 · CIFAR-100 | ECE stability | Hurt |
Surprising findings
- Adam optimizer with the PID-controlled dynamic objective drops CIFAR-100 ResNet35 accuracy to 63.5%, far below the 73.8% baseline.
- Post-hoc temperature scaling and vector scaling are not always worse; on some MCE metrics the proposed method is worse than the baselines (e.g., CIFAR-100 ResNet18 MCE 0.068 vs 0.052 for TS-AvUC).
Limitations
- No theoretical analysis of how gradient decay affects confidence distribution.
- Calibration responds slowly to β changes, implying a time lag that the PID controller handles only empirically.
- The learning-rate compensation assumes uniform sample probabilities in [0,1], which may not hold during training.
Experimental setup
Datasets: CIFAR-10 CIFAR-100 SVHN 102 Flower Tiny-ImageNet VisDrone COCO
Benchmarks: CIFAR-10 CIFAR-100 SVHN 102 Flower Tiny-ImageNet VisDrone COCO
Metrics: ECE MCE AdaECE accuracy
Baselines: Histogram Binning Temperature Scaling Vector Scaling TS-AvUC CosFace Center loss DCA Softmax cross-entropy
Builds on: temperature scaling DCA label smoothing
Closest papers by meaning
- Uncertainty Weighted Gradients for Model Calibration (CVPR 2025 · similarity 0.84)
- An Effective Dynamic Gradient Calibration Method for Continual Learning (ICML 2024 · similarity 0.84)
- A Benchmark Study on Calibration (ICLR 2024 · similarity 0.84)
- On PI Controllers for Updating Lagrange Multipliers in Constrained Optimization (ICML 2024 · similarity 0.84)
- Enabling Few-Shot Learning with PID Control: A Layer Adaptive Optimizer (ICML 2024 · similarity 0.84)
- Calibration Bottleneck: Over-compressed Representations are Less Calibratable (ICML 2024 · similarity 0.83)
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