REVIEW 2 major objections 5 minor 19 references
Making Reliable and Flexible Decisions in Long-tailed Classification
T0 review · 2 major / 5 minor · reviewed 2026-08-10 · deepseek-v4-flash
Pith's one-line read A single decision-theoretic objective lets long-tailed classifiers be trained for the errors that actually matter, with no loss in accuracy or calibration.
desk verdict A practical cost-sensitive long-tailed method with strong empirical results, but the optimality claim rests on swapping log E g for E log g; that gap is fixable. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
The load-bearing object is the integrated gain $G(d) = \mathbb{E}_{(x_1,y_1),\dots,(x_N,y_N)\sim p_{\mathrm{test}}(x,y)}\mathbb{E}_{\theta\sim p(\theta|D)}\prod_i g(d_i|x_i,\theta)$, where the per-input decision gain is $g(d|x,\theta)=\prod_{y'} p(y'|x,\theta)^{U_{y',d}}$. This fuses the task-specific utility matrix $U$, the class-imbalance correction $p_{\mathrm{test}}(y)/p_{\mathrm{train}}(y)\propto 1/f(n_y)$, and a posterior over models into one quantity. The paper converts this quantity into the tractable lower bound $L(q,d=Y)$ of Eq. 10 using Jensen's inequality, importance sampling, and a particle approximation $q(\theta)=\sum_j w_j\delta(\theta-\theta_j)$, with a repulsive-force term from the KL divergence that keeps particles diverse. The same machinery supplies the test-time decision rule in Eq. 16.
What would settle it
Train RF-DLC on a long-tailed benchmark, then evaluate it on a held-out test set with a known non-uniform class distribution and compare against a version trained with the correct $p_{\mathrm{test}}(y)/p_{\mathrm{train}}(y)$ ratio; if the decision gain or accuracy is worse, the uniform-test assumption is the cause. A second check is to compare per-class feature statistics between training and test images for the same label, which would directly test the intra-class consistency assumption.
Extended reading notes
Core claim
The central claim is that optimal decision-making on long-tailed data can be written as one objective: maximize a variational lower bound on the integrated gain, the expected utility-weighted predictive likelihood under the test distribution. The training loss is $L(q,d=Y) = \sum_i \mathbb{E}_{\theta\sim q(\theta)}[\frac{1}{f(n_{y_i})}(\sum_{y'} U_{y',y_i}\log p(y'|x_i,\theta) + \log p(y_i|x_i,\theta))] - \mathrm{KL}(q(\theta)\|p(\theta)) + C$, with $q(\theta)$ represented by an ensemble of particles. At test time, the optimal decision for input $x^*$ is $d^* = \arg\max_d \sum_j \sum_{y'} U_{y',d} \log p(y'|x^*,\theta_j)$. The experiments report that a tail-sensitive utility lowers false-head errors on CIFAR10-LT, CIFAR100-LT, and ImageNet-LT, that a one-hot utility preserves or improves overall and tail accuracy, and that the resulting Bayesian predictive distribution improves calibration.
Load-bearing premise
The whole weighting scheme reduces to $1/f(n_y)$ only because the paper assumes the test set is class-uniform and that, within each class, test inputs match training inputs; if either fails, the objective reweights the wrong quantity.
Editorial extensions
If this is right
- A user can encode any asymmetric penalty in the utility matrix, and the same training and inference equations apply without changing the model family.
- With a tail-sensitive utility, false-head errors drop on CIFAR10-LT, CIFAR100-LT, and ImageNet-LT across tail regions of 25%, 50%, and 75%.
- With a one-hot utility, the framework reduces to a class-weighted Bayesian ensemble, and the reported overall and tail accuracies are at or above the compared long-tailed baselines.
- The Bayesian predictive distribution from the particle ensemble gives better AUC and lower ECE than maximum softmax and evidential uncertainty baselines.
- The ablation recommends the linear form $f(n_y)=n_y$, since larger growth rates between head and tail weights improve tail and overall accuracy.
Reading between the lines
- If the test set's class distribution is known and non-uniform, the same derivation suggests replacing $1/f(n_y)$ with $p_{\mathrm{test}}(y)/p_{\mathrm{train}}(y)$; the paper notes this as a limitation but does not test it.
- The inference-time rule in Eq. 16 improves FHR when applied to other baselines, so part of the reported gain may come from decision-time re-scoring rather than from the new training objective alone.
- The objective is a lower bound on the integrated gain, and the gap from the one-sample Monte Carlo approximation and Jensen's inequality is not measured; a tighter or multi-sample estimate could be tested.
- A regression analogue could be built by replacing the categorical decision gain with a continuous utility function, a direction the paper lists as future work.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper proposes RF-DLC, a Bayesian decision-theoretic framework for long-tailed classification. It defines an integrated gain that combines a task utility matrix with the training-data class distribution, derives a lower bound (Eq. 10) using importance sampling under Assumption 1, approximates the posterior with particles (Eq. 13) plus repulsive regularization (Eq. 15), and makes test decisions via Eq. (16). Experiments on CIFAR10/100-LT, ImageNet-LT, iNaturalist, and DermaMNIST report gains in False Head Rate, accuracy, and calibration, with ablations over utility values, f(ny), particle number, and repulsive force.
Significance. If the theoretical claims are established, the framework is a valuable contribution: it offers a principled way to inject asymmetric error costs into long-tailed training and provides an uncertainty estimate through the particle posterior. The paper is strong empirically in breadth: it includes multiple benchmarks, a new cost-oriented metric, an ensemble comparison in Table 9, a robustness study of utility values in Table 15, and comparisons with cost-sensitive baselines in Table 14. The two main concerns below concern the optimality claim of the test-time rule and the relation between the derived and implemented objectives; both are fixable in revision.
major comments (2)
- [Section 4.4, Eq. (16)] Equation (16) is presented as maximizing log G(d|x*,D), but it computes sum_j sum_{y'} U_{y',d} log p(y'|x*,theta_j), which is E_{q(theta)} log g(d|x*,theta). With the particle approximation of Eq. (13), log G(d|x*,D) is approximately log((1/M) sum_j exp(sum_{y'} U_{y',d} log p(y'|x*,theta_j))). Jensen's inequality gives log E_q g >= E_q log g, with strict inequality whenever the particles disagree, and the two objectives can have different argmax decisions. This is not a posterior-approximation artifact: it persists even if q equals the true posterior supported on the M particles. The paper's central assertion that RF-DLC makes optimal decisions according to Bayesian Decision Theory is therefore not established by the derivation. Please either add experiments using the correct log-sum-exp rule, or explicitly reframe Eq. (16) as an approximate decision rule and measure the decision gap relative to the exact rule.
- [Appendix E.2, Eq. (24)] The implemented training objective in Eq. (24) is not the derived objective in Eq. (10). Eq. (10) weights the entire per-sample term by 1/f(n_{y_i}) and has no alpha; Eq. (24) displays neither the 1/f(n_y) weighting nor the KL term, and introduces a tuned rescaling 1/alpha on the utility term, with alpha set differently per dataset in Table 10. If the class-count weighting is applied in the actual code around Eq. (24), the manuscript needs to show that explicitly; as written, the empirical method is not the objective whose derivation forms the paper's theoretical contribution. Since the paper claims that the utility matrix and variational strategy are directly derived from Bayesian Decision Theory (Section 1), this discrepancy must be resolved, and the sensitivity of results to alpha should be reported.
minor comments (5)
- [Section 5.3, Table 3] Because RF-DLC is an ensemble of M particles while most rows are single models, please state this in the main text and reference Table 9 at the first presentation of Table 3; as presented, the comparison is not apples-to-apples.
- [Section 5.6, Table 7] The growth-rate column in Table 7 appears to be the ratio of the last-class weight to the first-class weight, but the text calls it growth rate without defining it; please clarify the definition to avoid confusion.
- [Abstract and Section 1] The abstract and Section 1 use 'quantity' where 'quantify' is intended ('to quantity the mispredictions'); please fix the typo.
- [Section 4.2, Assumption 1] The limitations section mentions non-uniform testing distributions but not the failure of Assumption 1 (p_train(x|y)=p_test(x|y)); since the importance ratio in Eq. (9) depends on that assumption, please add a sentence noting this limitation and its potential effect on the objective.
- [Appendix E.2] The statement that code will be released after acceptance conflicts with the reproducibility emphasis of the empirical section; providing the code with the revision would substantially strengthen the paper.
Circularity Check
No significant circularity: the training objective is a genuine ELBO-style derivation and the utility matrix is a user input, not a fitted target; the only notable issue is a test-time approximation error, which is a correctness concern rather than a circular one.
full rationale
The derivation chain is self-contained. Eq. (4) defines the integrated gain from Bayesian decision theory; Eq. (10) is obtained by Jensen's inequality (Appendix C), importance sampling under Assumption 1, and the 1/f(n_y) ratio; the utility matrix U is a pre-defined user input, not a parameter fitted to the evaluation metrics. The tail-sensitive utility is aligned with the FHR metric, but that is cost-sensitive objective alignment, not a fitted parameter renamed as a prediction; Appendix F.4 shows the FHR improvement is robust across utility values, and the method is also evaluated on external accuracy and calibration benchmarks (Tables 3-5). The self-citation to Li et al. (2022) is used as a baseline (TLC) and as an uncertainty competitor, not as load-bearing support for the derivation, so it does not raise the circularity score. One non-circular concern is Eq. (16): the paper writes argmax_d log G(d|x*,D) ≈ argmax_d Σ_j Σ_{y'} U_{y',d} log p(y'|x*,θ_j), which replaces log E_{θ~q} g by E_{θ~q} log g; this is a correctness or approximation issue (the two objectives can disagree), not a circular reduction, and it does not affect the training derivation in Eq. (10). The limitations section also explicitly acknowledges the uniform-test and dataset-shift assumptions, consistent with a non-circular derivation from stated assumptions.
Assumptions & free parameters
free parameters (6)
- Importance weighting form f(n_y) =
linear f(n_y)=n_y (selected after ablation vs sqrt, log, effective number, constant)
- Utility rescaling factor alpha =
0.002 (CIFAR10-LT), 0.3 (CIFAR100-LT), 50 (ImageNet-LT), 100 (iNaturalist)
- Repulsive force weight lambda =
5e-4 (CIFAR), 2e-4 (ImageNet-LT and iNaturalist), swept in Table 8
- Annealing time constant tau for repulsive force =
40 (CIFAR), 20 (ImageNet-LT and iNaturalist)
- Number of particles M =
3 for most experiments; up to 6 recommended in Fig. 2b
- Utility values in tail-sensitive matrix =
-1 for discouraged mispredictions, 1 for correct decisions
assumptions (6)
- domain assumption Assumption 1: intra-class consistency p_train(x|y)=p_test(x|y)
- domain assumption Testing distribution is uniform over classes: p_test(y)=constant
- ad hoc to paper The decision gain has the product form g(d|x,theta)=prod_{y'} p(y'|x,theta)^{u(y',d)}
- domain assumption The true label is treated as the optimal decision at training (d_i=y_i)
- standard math Jensen's inequality and Bayes' rule used to derive the lower bound
- ad hoc to paper Particle variational distribution with diagonal-covariance entropy approximation approximates the posterior
invented entities (1)
-
False Head Rate (FHR) metric
independent evidence
Cite this review
Pith. "Pith review of Making Reliable and Flexible Decisions in Long-tailed Classification." pith.science (2026). https://pith.science/paper/H2TXSNH3
@misc{pith2026250114090,
author = {Pith},
title = {Pith review of: Making Reliable and Flexible Decisions in Long-tailed Classification},
year = {2026},
howpublished = {\url{https://pith.science/paper/H2TXSNH3}},
note = {Machine review of arXiv:2501.14090}
}
read the original abstract
Long-tailed classification is challenging due to its heavy imbalance in class probabilities. While existing methods often focus on overall accuracy or accuracy for tail classes, they overlook a critical aspect: certain types of errors can carry greater risks than others in real-world long-tailed problems. For example, misclassifying patients (a tail class) as healthy individuals (a head class) entails far more serious consequences than the reverse scenario. To address this critical issue, we introduce Making Reliable and Flexible Decisions in Long-tailed Classification (RF-DLC), a novel framework aimed at reliable predictions in long-tailed problems. Leveraging Bayesian Decision Theory, we introduce an integrated gain to seamlessly combine long-tailed data distributions and the decision-making procedure. We further propose an efficient variational optimization strategy for the decision risk objective. Our method adapts readily to diverse utility matrices, which can be designed for specific tasks, ensuring its flexibility for different problem settings. In empirical evaluation, we design a new metric, False Head Rate, to quantify tail-sensitivity risk, along with comprehensive experiments on multiple real-world tasks, including large-scale image classification and uncertainty quantification, to demonstrate the reliability and flexibility of our method.
Figures
Reference graph
Works this paper leans on
-
[8]
Detection of flying birds in airport monitoring based on improved yolov5
Xiaohang Shi, Jun Hu, Xueyue Lei, and Shiyou Xu. Detection of flying birds in airport monitoring based on improved yolov5. In 2021 6th International Conference on Intelligent Computing and Signal Processing (ICSP), pp. 1446–
work page 2021
-
[10]
We will release the code after acceptance
The optimal values of those hyper-parameters are determined by grid search. We will release the code after acceptance. Table 10: Hyper-parameter configurations. Dataset Base Model Optimizer Batch Size Learning Rate T raining Epochs Discrepancy Ratio λ τ α CIFAR10-LT ResNet32 SGD 128 0.1 200 linear 5e-4 40 0.002 CIFAR100-LT ResNet32 SGD 128 0.1 200 linear ...
work page 2025
-
[11]
Learning to model the tail.Advances in Neural Information Processing Systems, 30,
15 Published in Transactions on Machine Learning Research (01/2025) Yu-Xiong Wang, Deva Ramanan, and Martial Hebert. Learning to model the tail.Advances in Neural Information Processing Systems, 30,
work page 2025
-
[13]
and then explored by Liu et al. (2019a); Korba et al. (2020); D’Angelo & Fortuin (2020). Instead of directly modeling the gradient flow, our framework optimizes the particles through stochastic gradient descent (SGD), with repulsive force induced by the integrated gain objective. Compared to existing particle optimization, our method is easy and cheap to ...
work page 2019
-
[15]
Therefore, the computational cost of our method is comparable to existing ensemble models
and TLC (Li et al., 2022), in which the first few layers in neural networks are shared among all particles. Therefore, the computational cost of our method is comparable to existing ensemble models. Besides, compared with gradient-flow-based BNN like D’Angelo & Fortuin (2021), which typically uses 20 particles, our model is far more efficient with no more...
work page 2021
-
[16]
Classes are equally split into three class regions (head, med and tail)
45.27 1,408,784 RF-DLC (ours) 44.68 1,408,784 F Additional Experimental Results F.1 Full Experimental Results on Classification We list the full experimental results of top-1 accuracy in Table 12, including the results on iNaturalist (Van Horn et al., 2018). Classes are equally split into three class regions (head, med and tail). For example, there are 33...
work page 2018
-
[18]
78.16 84.51 79.62 67.63 21.88 10.27 22.01 34.53 Bayesian (RF-DLC) 80.62 88.47 81.82 63.05 10.87 6.37 11.09 16.71 decision-making processes. For example, the method in Section 2 of Elkan (2001) does not consider specific error types during the training phase, and fails to incorporate the utility matrix during testing. The Bayesian method in Section 4 of El...
work page 2001
-
[19]
It specifically avoids mispredicting some classes as other classes
is one of the key contributions of this paper. It specifically avoids mispredicting some classes as other classes. To understand the effect of utility functions, we add an ablation study in Table 16, where Eq. 16 with tail-sensitive utility is added to baselines at inference time. Adding Eq. 16 improves the FHR performance and maintains the ACC, which dem...
work page 2025
Show all 19 references
-
[1999]
Subjective Logic: A formalism for reasoning under uncertainty
13 Published in Transactions on Machine Learning Research (01/2025) Audun Jsang. Subjective Logic: A formalism for reasoning under uncertainty. Springer Publishing Company, Incor- porated,
2025
-
[2001]
* means the results are obtained from a slim version of ResNet50 due to GPU memory limits
could not effectively solve the decision-making problem in long-tailed classification due to their lack of a holistic approach that integrates distributional shift and 20 Published in Transactions on Machine Learning Research (01/2025) Table 12: Full top-1 accuracy results (%)...
2025
-
[2010]
The devil is in the tails: Fine-grained classification in the wild.arXiv preprint arXiv:1709.01450,
Grant Van Horn and Pietro Perona. The devil is in the tails: Fine-grained classification in the wild.arXiv preprint arXiv:1709.01450,
-
[2013]
Nurse care activity recognition: A cost-sensitive ensemble approach to handle imbalanced class problem in the wild
Arafat Rahman, Iqbal Hassan, and Md Atiqur Rahman Ahad. Nurse care activity recognition: A cost-sensitive ensemble approach to handle imbalanced class problem in the wild. InAdjunct Proceedings of the 2021 ACM International Joint Conference on Pervasive and Ubiquitous Computin...
2021
-
[2016]
Loss-calibrated approximate inference in bayesian neural networks
Adam D Cobb, Stephen J Roberts, and Yarin Gal. Loss-calibrated approximate inference in bayesian neural networks. arXiv preprint arXiv:1805.03901,
-
[2017]
Cost-sensitive learning and the class imbalance problem.Encyclopedia of machine learning, 2011:231–235,
Charles X Ling and Victor S Sheng. Cost-sensitive learning and the class imbalance problem.Encyclopedia of machine learning, 2011:231–235,
2011
-
[2018]
Predictive uncertainty estimation via prior networks.Advances in Neural Infor- mation Processing Systems, 31,
14 Published in Transactions on Machine Learning Research (01/2025) Andrey Malinin and Mark Gales. Predictive uncertainty estimation via prior networks.Advances in Neural Infor- mation Processing Systems, 31,
2025
-
[2019]
Cost-sensitive learning methods for imbalanced data
Nguyen Thai-Nghe, Zeno Gantner, and Lars Schmidt-Thieme. Cost-sensitive learning methods for imbalanced data. In The 2010 International joint conference on neural networks (IJCNN), pp. 1–8. IEEE,
2010
-
[2020]
Loss-calibrated expectation propagation for approximate bayesian decision- making
Michael J Morais and Jonathan W Pillow. Loss-calibrated expectation propagation for approximate bayesian decision- making. arXiv preprint arXiv:2201.03128,
-
[2021]
Feature space augmentation for long-tailed data
12 Published in Transactions on Machine Learning Research (01/2025) Peng Chu, Xiao Bian, Shaopeng Liu, and Haibin Ling. Feature space augmentation for long-tailed data. InComputer Vision–ECCV 2020: 16th European Conference, Glasgow, UK, August 23–28, 2020, Proceedings, Part XX...
2025
-
[2022]
particle
16 Published in Transactions on Machine Learning Research (01/2025) A Related Model Architectures The model architecture of our method is an ensemble of multiple individual models. This architecture belongs to a general type of Bayesian neural networks, called particle-based B...
2025
Reviewed August 10, 2026 · model on record in the stance chip above.
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