Evaluating few-shot learning models requires a focus on metrics and testing protocols that account for their ability to learn from minimal data. The primary goal is to measure how well the model generalizes to new tasks or classes it hasn’t seen during training. Common evaluation metrics include accuracy, precision, recall, and F1-score, but accuracy is often the default due to its simplicity. For example, in a 5-way 5-shot task (classifying among 5 categories with 5 examples each), accuracy directly reflects how many test samples the model labels correctly. However, these metrics should be averaged across multiple test episodes (distinct subsets of data) to reduce variance, as performance can fluctuate significantly depending on the specific examples provided.
A key aspect of evaluation is episodic testing, which mimics the few-shot scenario by structuring tests into small, self-contained tasks. Each episode includes a support set (the few labeled examples) and a query set (unlabeled data to predict). For instance, a model trained on MiniImageNet (a dataset for few-shot image classification) might be tested across 1,000 randomly sampled episodes, each with different classes and examples. This approach ensures the model isn’t overfitting to specific data splits and provides a statistically reliable performance estimate. Developers often report mean accuracy and standard deviation over these episodes to highlight consistency.
Finally, cross-domain evaluation and comparison to baselines are critical. A model might perform well on MiniImageNet but struggle on a dissimilar dataset like CUB-200 (bird species), revealing limitations in generalization. Comparing against simpler approaches, like fine-tuning a pretrained model on the few examples, helps assess whether the few-shot method adds value. Additionally, computational efficiency—how quickly the model adapts to new tasks—is practical for real-world use. For example, a model that achieves 80% accuracy but takes hours to adapt might be less useful than one with 75% accuracy that adapts in seconds. These considerations ensure the evaluation reflects both performance and practicality.