SimpleShot: Revisiting Nearest-Neighbor Classification for Few-Shot Learning

12 Nov 2019  ·  Yan Wang, Wei-Lun Chao, Kilian Q. Weinberger, Laurens van der Maaten ·

Few-shot learners aim to recognize new object classes based on a small number of labeled training examples. To prevent overfitting, state-of-the-art few-shot learners use meta-learning on convolutional-network features and perform classification using a nearest-neighbor classifier. This paper studies the accuracy of nearest-neighbor baselines without meta-learning. Surprisingly, we find simple feature transformations suffice to obtain competitive few-shot learning accuracies. For example, we find that a nearest-neighbor classifier used in combination with mean-subtraction and L2-normalization outperforms prior results in three out of five settings on the miniImageNet dataset.

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Task Dataset Model Metric Name Metric Value Global Rank Result Benchmark
Few-Shot Image Classification Dirichlet CUB-200 (5-way, 1-shot) Simpleshot 1:1 Accuracy 70.6 # 5
Few-Shot Image Classification Dirichlet CUB-200 (5-way, 5-shot) Simpleshot 1:1 Accuracy 87.5 # 4
Few-Shot Image Classification Dirichlet Mini-Imagenet (5-way, 1-shot) Simpleshot 1:1 Accuracy 63.0 # 5
Few-Shot Image Classification Dirichlet Mini-Imagenet (5-way, 5-shot) Simpleshot 1:1 Accuracy 80.1 # 5
Few-Shot Image Classification Dirichlet Tiered-Imagenet (5-way, 1-shot) Simpleshot 1:1 Accuracy 69.6 # 6
Few-Shot Image Classification Dirichlet Tiered-Imagenet (5-way, 5-shot) Simpleshot 1:1 Accuracy 84.7 # 6
Few-Shot Image Classification Mini-Imagenet 5-way (1-shot) SimpleShot (CL2N-DenseNet) Accuracy 64.29 # 55
Few-Shot Image Classification Mini-Imagenet 5-way (5-shot) SimpleShot (CL2N-DenseNet) Accuracy 81.5 # 41

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