Papers › Realistic Evaluation of Transductive Few-Shot Learning

Realistic Evaluation of Transductive Few-Shot Learning

24 Apr 2022NeurIPS 2021 12arXiv:2204.11181archive 2025-07-28

Olivier Veilleux, Malik Boudiaf, Pablo Piantanida, Ismail Ben Ayed

Transductive inference is widely used in few-shot learning, as it leverages the statistics of the unlabeled query set of a few-shot task, typically yielding substantially better performances than its inductive counterpart. The current few-shot benchmarks use perfectly class-balanced tasks at inference. We argue that such an artificial regularity is unrealistic, as it assumes that the marginal label probability of the testing samples is known and fixed to the uniform distribution. In fact, in realistic scenarios, the unlabeled query sets come with arbitrary and unknown label marginals. We introduce and study the effect of arbitrary class distributions within the query sets of few-shot tasks at inference, removing the class-balance artefact. Specifically, we model the marginal probabilities of the classes as Dirichlet-distributed random variables, which yields a principled and realistic sampling within the simplex. This leverages the current few-shot benchmarks, building testing tasks with arbitrary class distributions. We evaluate experimentally state-of-the-art transductive methods over 3 widely used data sets, and observe, surprisingly, substantial performance drops, even below inductive methods in some cases. Furthermore, we propose a generalization of the mutual-information loss, based on α-divergences, which can handle effectively class-distribution variations. Empirically, we show that our transductive α-divergence optimization outperforms state-of-the-art methods across several data sets, models and few-shot settings. Our code is publicly available at https://github.com/oveilleux/Realistic_Transductive_Few_Shot.

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Tasks

Few-Shot Learning

Results from the paper archive 2025-07-28

TaskDatasetModelMetricValueRank at snapshotLeaderboardReport
Few-Shot Image Classification Dirichlet CUB-200 (5-way, 1-shot) \alpha-TIM 1:1 Accuracy 75.7 #2 of 8 Archive leaderboard report
Few-Shot Image Classification Dirichlet CUB-200 (5-way, 5-shot) \alpha-TIM 1:1 Accuracy 89.8 #2 of 8 Archive leaderboard report
Few-Shot Image Classification Dirichlet Mini-Imagenet (5-way, 1-shot) \alpha-TIM 1:1 Accuracy 67.4 #2 of 12 Archive leaderboard report
Few-Shot Image Classification Dirichlet Mini-Imagenet (5-way, 5-shot) \alpha-TIM 1:1 Accuracy 82.5 #2 of 12 Archive leaderboard report
Few-Shot Image Classification Dirichlet Tiered-Imagenet (5-way, 1-shot) \alpha-TIM 1:1 Accuracy 74.4 #3 of 9 Archive leaderboard report
Few-Shot Image Classification Dirichlet Tiered-Imagenet (5-way, 5-shot) \alpha-TIM 1:1 Accuracy 86.6 #1 of 9 Archive leaderboard report

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