About poolformer as a tool for demonstration of MetaFormer about poolformer

[yuweihao]

Hi @YoojLee ,

Thanks for your insightful discussion.

1. In my opinion, the core of MetaFormer is the repeated MetaFormer blocks. Thus, those models using hierarchical structure, like PVT, Swin and PoolFormer, are regarded as MetaFormer models.

2. For 4-stage hierarchical structure, the four patch embeddings shown in that paper actually can also be called downsampling layers similar to ResNet. Downsampling can also mix tokens, but its main function is to reduce resolution and increase channel numbers. ResNet and PoolFormer have similar hierarchical structures, the better performance of PoolFormer demonstrates the superior of MetaForemer. You may also refer #43.

[YoojLee]

Thanks for your reply!

I just want to confirm that what I understand is right. If I get your comment correct, the suggested MetaFormer concept is the mere stack of MetaFormer Block (which consists of normalization, token&channel mixer, and residual connection). Thus, regardless of the extent of inductive bias or whether overall architecture follows a hierarchical structure, the models with repetition of MetaFormer blocks become one of the MetaFormers.