Efficient feature selection for pre-trained vision transformers

Handcrafted layer-wise vision transformers have demonstrated remarkable performance in image classification. However, their high computational cost limits their practical applications. In this paper, we first identify and highlight the data-independent feature redundancy in pre-trained Vision Transformer (ViT) models. Based on this observation, we explore the feasibility of searching for the best substructure within the original pre-trained model. To this end, we propose EffiSelecViT, a novel pruning method aimed at reducing the computational cost of ViTs while preserving their accuracy. EffiSelecViT introduces importance scores for both self-attention heads and Multi-Layer Perceptron (MLP) neurons in pre-trained ViT models. L1 regularization is applied to constrain and learn these scores. In this simple way, components that are crucial for model performance are assigned higher scores, while those with lower scores are identified as less important and subsequently pruned. Experimental results demonstrate that EffiSelecViT can prune DeiT-B to retain only 64% of FLOPs while maintaining accuracy. This efficiency-accuracy trade-off is consistent across various ViT architectures. Furthermore, qualitative analysis reveals enhanced information expression in the pruned models, affirming the effectiveness and practicality of EffiSelecViT. The code is available at https://github.com/ZJ6789/EffiSelecViT.