arXiv:2608.10372cs.LG2026-08

提出可逆对数变换,校准预测置信度且不改变分类结果。

Invertible Logits Transformation for Accuracy-Preserving Post-Hoc Uncertainty Calibration

  • 用共享的MLP对原始输出进行逐元素变换,参数与类别数无关。
  • 在多个图像分类数据集上校准误差低于现有方法,准确率保持不变。
  • 无需复杂约束即可保持预测顺序,适合大类别场景使用。

后训练校准可使分类器的预测置信度与其实际准确率对齐,无需重新训练。理想校准器应能纠正非线性误校准、适应大规模类别空间,并保留原始预测结果;但现有方法通常至少违反其中一项——温度缩放表达能力不足,更灵活的参数化方法参数量随类别数C增长,其他高表达方法则可能改变类别得分排序甚至预测结果。我们提出「可逆对数变换(InvLT)」,将一个学习得到的标量MLP f:ℝ→ℝ逐元素应用于预软最大化分值(pre-softmax logits),通过跨维度共享f使参数量独立于类别数C。通过配对逆网络软性鼓励f的单调性,避免了以往单调校准器所需的数值积分计算开销,同时在所有评估场景中实证保持了原始分类准确率。在标准图像分类基准和多种架构上,InvLT始终优于广泛对比的后训练基线方法,在标准校准指标上表现更优。

原文摘要 · Abstract (English)

Post-hoc calibration aligns a classifier's predicted confidences with its empirical accuracy without retraining. An ideal calibrator should correct nonlinear miscalibration, scale gracefully to large label spaces, and preserve the original predictions; existing methods typically violate at least one of these properties---temperature scaling lacks expressivity, more flexible parametric alternatives introduce parameters that grow with the number of classes $C$, and other expressive methods do not preserve the rank ordering of class scores and may alter the predicted class. We propose \textbf{Invertible Logits Transformation (InvLT)}, which applies a learned scalar MLP $f:\mathbb{R}\to\mathbb{R}$ element-wise to the pre-softmax logits. Sharing $f$ across all logit dimensions makes the parameter count independent of $C$. Monotonicity of $f$---and hence preservation of the argmax prediction---is softly encouraged via a paired inverse network rather than enforced through the numerical integration required by prior monotone calibrators; this avoids their computational overhead while empirically preserving the original classification accuracy in every setting we evaluate. Across standard image classification benchmarks and a range of architectures, InvLT consistently outperforms a broad set of post-hoc baselines on standard calibration metrics.

不确定性校准后训练分类准确率可逆变换

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