GP-Adapter: Gaussian Process CLIP-Adapter for Few-Shot Out-of-Distribution Detection
This work addresses the lack of reliable uncertainty estimation in CLIP under few-shot and out-of-distribution (OOD) settings by proposing GP-Adapter, a training-free, plug-and-play framework. GP-Adapter constructs modality-specific one-class Gaussian processes on frozen CLIP features—employing an RBF kernel for images and a linear kernel for text—and fuses predictive statistics from both modalities to produce variance-aware confidence scores. As the first approach to integrate Gaussian process-based uncertainty modeling into CLIP, GP-Adapter enables effective few-shot classification and OOD detection without fine-tuning, incurs low memory overhead, and complements existing prompt-learning methods. Experiments demonstrate competitive classification performance on ImageNet and multiple OOD benchmarks, along with significantly improved OOD detection accuracy.