Squeeze-and-Excitation Networks _(arXiv)

By Jie Hu^[1], Li Shen^[2], Gang Sun^[1].

Momenta^[1] and University of Oxford^[2].

Approach

Figure 1: Diagram of a Squeeze-and-Excitation building block.

Figure 2: Schema of SE-Inception and SE-ResNet modules. We set r=16 in all our models.

Implementation

In this repository, Squeeze-and-Excitation Networks are implemented by Caffe.

Augmentation

Method	Settings
Random Mirror	True
Random Crop	8% ~ 100%
Aspect Ratio	3/4 ~ 4/3
Random Rotation	-10° ~ 10°
Pixel Jitter	-20 ~ 20

Note:

To achieve efficient training and testing, we combine the consecutive operations channel-wise scale and element-wise summation into a single layer "Axpy" in the architectures with skip-connections, resulting in a considerable reduction in memory cost and computational burden.
In addition, we found that the implementation for global average pooling on GPU supported by cuDNN and BVLC/caffe is less efficient. In this regard, we re-implement the operation which achieves significant acceleration.

Trained Models

Table 1. Single crop validation error on ImageNet-1k (center 224x224 crop from resized image with shorter side = 256). The SENet^* is one of our superior models used in ILSVRC 2017 Image Classification Challenge where we won the 1st place (Team name: WMW).

Model	Top-1	Top-5	Size	Caffe Model
SE-BN-Inception	23.62	7.04	46 M	GoogleDrive
SE-ResNet-50	22.37	6.36	107 M	GoogleDrive
SE-ResNet-101	21.75	5.72	189 M	GoogleDrive
SE-ResNet-152	21.34	5.54	256 M	GoogleDrive
SE-ResNeXt-50 (32 x 4d)	20.97	5.54	105 M	GoogleDrive
SE-ResNeXt-101 (32 x 4d)	19.81	4.96	187 M	GoogleDrive
SENet^*	18.68	4.47	440 M	GoogleDrive

Here we obtain better performance than those reported in the paper. We re-train the SENets described in the paper on a single GPU server with 8 NVIDIA Titan X cards, using a mini-batch of 256 and a initial learning rate of 0.1 with more epoches. In contrast, the results reported in the paper were obtained by training the networks with a larger batch size (1024) and learning rate (0.6) across 4 servers.

Third-party re-implementations

Caffe. SE-mudolues are integrated with a modificated ResNet-50 using a stride 2 in the 3x3 convolution instead of the first 1x1 convolution which obtains better performance: Repository.
TensorFlow. SE-modules are integrated with a pre-activation ResNet-50 which follows the setup in fb.resnet.torch: Repository.
MatConvNet. All the released SENets are imported into MatConvNet: Repository.

Citation

If you use Squeeze-and-Excitation Networks in your research, please cite the paper:

@article{hu2017,
  title={Squeeze-and-Excitation Networks},
  author={Jie Hu and Li Shen and Gang Sun},
  journal={arXiv preprint arXiv:1709.01507},
  year={2017}
}

fleapo/SENet

Squeeze-and-Excitation Networks (arXiv)