Focal Modulation Networks

This is the official Pytorch implementation of FocalNets:

"Focal Modulation Networks" by Jianwei Yang, Chunyuan Li, Xiyang Dai, Lu Yuan and Jianfeng Gao.

News

[11/02/2022] We wrote a blog post to introduce the insights and techniques behind our FocalNets in a plain way, check it out!
[10/31/2022] 💥 We achieved new SoTA with ~~64.2~~ 64.3 box mAP on COCO minival and ~~64.3~~ 64.4 box mAP on COCO test-dev based on the powerful OD method DINO! We used huge model size (700M) beating much larger attention-based models like SwinV2-G and BEIT-3. Checkoout our new version and stay tuned!
[09/20/2022] Our FocalNet has been accepted by NeurIPS 2022!
[04/02/2022] Create a gradio demo in huggingface space to visualize the modulation mechanism. Check it out!

Introduction

We propose FocalNets: Focal Modulation Networks, an attention-free architecture that achieves superior performance than SoTA self-attention (SA) methods across various vision benchmarks. SA is an first interaction, last aggregation (FILA) process as shown above. Our Focal Modulation inverts the process by first aggregating, last interaction (FALI). This inversion brings several merits:

Translation-Invariance: It is performed for each target token with the context centered around it.
Explicit input-dependency: The modulator is computed by aggregating the short- and long-rage context from the input and then applied to the target token.
Spatial- and channel-specific: It first aggregates the context spatial-wise and then channel-wise, followed by an element-wise modulation.
Decoupled feature granularity: Query token preserves the invidual information at finest level, while coarser context is extracted surrounding it. They two are decoupled but connected through the modulation operation.
Easy to implement: We can implement both context aggregation and interaction in a very simple and light-weight way. It does not need softmax, multiple attention heads, feature map rolling or unfolding, etc.

Before getting started, see what our FocalNets have learned to perceive images and where to modulate!

Finally, FocalNets are built with convolutional and linear layers, but goes beyond by proposing a new modulation mechanism that is simple, generic, effective and efficient. We hereby recommend:

Focal-Modulation May be What We Need for Visual Modeling!

Getting Started

Please follow get_started_for_image_classification to get started for image classification.
Please follow get_started_for_object_detection to get started for object detection.
Please follow get_started_for_semantic_segmentation to get started for semantic segmentation.

Benchmarking

Image Classification on ImageNet-1K

ImageNet-1K Pretrained

Strict comparison with multi-scale Swin and Focal Transformers:

Model	Depth	Dim	Kernels	#Params. (M)	FLOPs (G)	Throughput (imgs/s)	Top-1	Download
FocalNet-T	[2,2,6,2]	96	[3,5]	28.4	4.4	743	82.1	ckpt/config/log
FocalNet-T	[2,2,6,2]	96	[3,5,7]	28.6	4.5	696	82.3	ckpt/config/log
FocalNet-S	[2,2,18,2]	96	[3,5]	49.9	8.6	434	83.4	ckpt/config/log
FocalNet-S	[2,2,18,2]	96	[3,5,7]	50.3	8.7	406	83.5	ckpt/config/log
FocalNet-B	[2,2,18,2]	128	[3,5]	88.1	15.3	280	83.7	ckpt/config/log
FocalNet-B	[2,2,18,2]	128	[3,5,7]	88.7	15.4	269	83.9	ckpt/config/log

Strict comparison with isotropic ViT models:

Model	Depth	Dim	Kernels	#Params. (M)	FLOPs (G)	Throughput (imgs/s)	Top-1	Download
FocalNet-T	12	192	[3,5,7]	5.9	1.1	2334	74.1	ckpt/config/log
FocalNet-S	12	384	[3,5,7]	22.4	4.3	920	80.9	ckpt/config/log
FocalNet-B	12	768	[3,5,7]	87.2	16.9	300	82.4	ckpt/config/log

Object Detection on COCO

Mask R-CNN

Backbone	Kernels	Lr Schd	#Params. (M)	FLOPs (G)	box mAP	mask mAP	Download
FocalNet-T	[9,11]	1x	48.6	267	45.9	41.3	ckpt/config/log
FocalNet-T	[9,11]	3x	48.6	267	47.6	42.6	ckpt/config/log
FocalNet-T	[9,11,13]	1x	48.8	268	46.1	41.5	ckpt/config/log
FocalNet-T	[9,11,13]	3x	48.8	268	48.0	42.9	ckpt/config/log
FocalNet-S	[9,11]	1x	70.8	356	48.0	42.7	ckpt/config/log
FocalNet-S	[9,11]	3x	70.8	356	48.9	43.6	ckpt/config/log
FocalNet-S	[9,11,13]	1x	72.3	365	48.3	43.1	ckpt/config/log
FocalNet-S	[9,11,13]	3x	72.3	365	49.3	43.8	ckpt/config/log
FocalNet-B	[9,11]	1x	109.4	496	48.8	43.3	ckpt/config/log
FocalNet-B	[9,11]	3x	109.4	496	49.6	44.1	ckpt/config/log
FocalNet-B	[9,11,13]	1x	111.4	507	49.0	43.5	ckpt/config/log
FocalNet-B	[9,11,13]	3x	111.4	507	49.8	44.1	ckpt/config/log

Other detection methods

Backbone	Kernels	Method	Lr Schd	#Params. (M)	FLOPs (G)	box mAP	Download
FocalNet-T	[11,9,9,7]	Cascade Mask R-CNN	3x	87.1	751	51.5	ckpt/config/log
FocalNet-T	[11,9,9,7]	ATSS	3x	37.2	220	49.6	ckpt/config/log
FocalNet-T	[11,9,9,7]	Sparse R-CNN	3x	111.2	178	49.9	ckpt/config/log

Semantic Segmentation on ADE20K

Resolution 512x512 and Iters 160k

Backbone	Kernels	Method	#Params. (M)	FLOPs (G)	mIoU	mIoU (MS)	Download
FocalNet-T	[9,11]	UPerNet	61	944	46.5	47.2	ckpt/config/log
FocalNet-T	[9,11,13]	UPerNet	61	949	46.8	47.8	ckpt/config/log
FocalNet-S	[9,11]	UPerNet	83	1035	49.3	50.1	ckpt/config/log
FocalNet-S	[9,11,13]	UPerNet	84	1044	49.1	50.1	ckpt/config/log
FocalNet-B	[9,11]	UPerNet	124	1180	50.2	51.1	ckpt/config/log
FocalNet-B	[9,11,13]	UPerNet	126	1192	50.5	51.4	ckpt/config/log

Visualizations

There are three steps in our FocalNets:

Contexualization with depth-wise conv;
Multi-scale aggregation with gating mechanism;
Modulator derived from context aggregation and projection.

We visualize them one by one.

Depth-wise convolution kernels learned in FocalNets:

Yellow colors represent higher values. Apparently, FocalNets learn to gather more local context at earlier stages while more global context at later stages.

Gating maps at last layer of FocalNets for different input images:

From left to right, the images are input image, gating map for focal level 1,2,3 and the global context. Clearly, our model has learned where to gather the context depending on the visual contents at different locations.

Modulator learned in FocalNets for different input images:

The modulator derived from our model automatically learns to focus on the foreground regions.

For visualization by your own, please refer to visualization notebook.

Citation

If you find this repo useful to your project, please consider to cite it with following bib:

@misc{yang2022focal,
      title={Focal Modulation Networks}, 
      author={Jianwei Yang and Chunyuan Li and Xiyang Dai and Jianfeng Gao},
      journal={Advances in Neural Information Processing Systems (NeurIPS)},
      year={2022}
}

Acknowledgement

Our codebase is built based on Swin Transformer and Focal Transformer. To achieve the SoTA object detection performance, we heavily rely on the most advanced method DINO and the advices from the authors. We thank the authors for the nicely organized code!

Contributing

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Trademarks

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crazyfrogspb/FocalNet