mmselfsup/docs/en/algorithms/byol.md

# BYOL

## Bootstrap your own latent: A new approach to self-supervised Learning

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**B**ootstrap **Y**our **O**wn **L**atent (BYOL) is a new approach to self-supervised image representation learning. BYOL relies on two neural networks, referred to as online and target networks, that interact and learn from each other. From an augmented view of an image, we train the online network to predict the target network representation of the same image under a different augmented view. At the same time, we update the target network with a slow-moving average of the online network.

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## Citation

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```bibtex
@inproceedings{grill2020bootstrap,
  title={Bootstrap your own latent: A new approach to self-supervised learning},
  author={Grill, Jean-Bastien and Strub, Florian and Altch{\'e}, Florent and Tallec, Corentin and Richemond, Pierre H and Buchatskaya, Elena and Doersch, Carl and Pires, Bernardo Avila and Guo, Zhaohan Daniel and Azar, Mohammad Gheshlaghi and others},
  booktitle={NeurIPS},
  year={2020}
}
```

## Models and Benchmarks

[Back to model_zoo.md](../../../docs/model_zoo.md)

In this page, we provide benchmarks as much as possible to evaluate our pre-trained models. If not mentioned, all models were trained on ImageNet1k dataset.


### VOC SVM / Low-shot SVM

The **Best Layer** indicates that the best results are obtained from which layers feature map. For example, if the **Best Layer** is **feature3**, its best result is obtained from the second stage of ResNet (1 for stem layer, 2-5 for 4 stage layers).

Besides, k=1 to 96 indicates the hyper-parameter of Low-shot SVM.

| Model     | Config setting                                                                      | Best Layer | SVM   | k=1   | k=2   | k=4   | k=8   | k=16  | k=32  | k=64  | k=96  |
| --------- | ----------------------------------------------------------------------------------- | ---------- | ----- | ----- | ----- | ----- | ----- | ----- | ----- | ----- | ----- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) | feature3   | 86.31 | 45.37 | 56.83 | 68.47 | 74.12 | 78.30 | 81.53 | 83.56 | 84.73 |

### Classification

The classification benchmarks includes 3 downstream task datasets, **ImageNet**,  **iNaturalist2018** and **Places205**. If not specified, the results are  Top-1 (%).

#### ImageNet Linear Evaluation

The **Feature1 - Feature5** don't have the GlobalAveragePooling, the feature map is pooled to the specific dimensions and then follows a Linear layer to do the classification. Please refer to [resnet50_mhead_8xb32-steplr-90e.py](../../benchmarks/classification/imagenet/resnet50_mhead_8xb32-steplr-90e_in1k.py) for details of config.

The **AvgPool** result is obtained from Linear Evaluation with GlobalAveragePooling. Please refer to [{file name}]() for details of config.

| Model     | Config                                                                              | Feature1 | Feature2 | Feature3 | Feature4 | Feature5 | AvgPool |
| --------- | ----------------------------------------------------------------------------------- | -------- | -------- | -------- | -------- | -------- | ------- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |          |          |          |          |          | 67.68   |

#### iNaturalist2018 Linear Evaluation

Please refer to [resnet50_mhead_8xb32-steplr-84e_inat18.py](../../benchmarks/classification/inaturalist2018/resnet50_mhead_8xb32-steplr-84e_inat18.py) and [{file name}]() for details of config.

| Model     | Config                                                                              | Feature1 | Feature2 | Feature3 | Feature4 | Feature5 | AvgPool |
| --------- | ----------------------------------------------------------------------------------- | -------- | -------- | -------- | -------- | -------- | ------- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |          |          |          |          |          |         |

#### Places205 Linear Evaluation

Please refer to [resnet50_mhead_8xb32-steplr-28e_places205.py](../../benchmarks/classification/inaturalist2018/resnet50_mhead_8xb32-steplr-28e_places205.py) and [{file name}]() for details of config.

| Model     | Config                                                                              | Feature1 | Feature2 | Feature3 | Feature4 | Feature5 | AvgPool |
| --------- | ----------------------------------------------------------------------------------- | -------- | -------- | -------- | -------- | -------- | ------- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |          |          |          |          |          |         |

#### Semi-Supervised Classification

- In this benchmark, the necks or heads are removed and only the backbone CNN is evaluated by appending a linear classification head. All parameters are fine-tuned.
- When training with 1% ImageNet, we find hyper-parameters especially the learning rate greatly influence the performance. Hence, we prepare a list of settings with the base learning rate from `{0.001, 0.01, 0.1}` and the learning rate multiplier for the head from `{1, 10, 100}`. We choose the best performing setting for each method. The setting of parameters are indicated in the file name. The learning rate is indicated like `1e-1`, `1e-2`, `1e-3` and the learning rate multiplier is indicated like `head1`, `head10`, `head100`.
- Please use --deterministic in this benchmark.

Please refer to the directories `configs/benchmarks/classification/imagenet/imagenet_1percent/` of 1% data and `configs/benchmarks/classification/imagenet/imagenet_10percent/` 10% data for details.

| Model     | Pretrain Config                                                                     | Fine-tuned Config | Top-1 (%) | Top-5 (%) |
| --------- | ----------------------------------------------------------------------------------- | ----------------- | --------- | --------- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |                   |           |           |

### Detection

The detection benchmarks includes 2 downstream task datasets, **Pascal VOC 2007 + 2012** and **COCO2017**. This benchmark follows the evluation protocols set up by MoCo.

#### Pascal VOC 2007 + 2012

Please refer to [faster_rcnn_r50_c4_mstrain_24k.py](../../benchmarks/mmdetection/voc0712/faster_rcnn_r50_c4_mstrain_24k.py) for details of config.

| Model     | Config                                                                              | mAP | AP50 |
| --------- | ----------------------------------------------------------------------------------- | --- | ---- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |     |      |

#### COCO2017

Please refer to [mask_rcnn_r50_fpn_mstrain_1x.py](../../benchmarks/mmdetection/coco/mask_rcnn_r50_fpn_mstrain_1x.py) for details of config.

| Model     | Config                                                                              | mAP(Box) | AP50(Box) | AP75(Box) | mAP(Mask) | AP50(Mask) | AP75(Mask) |
| --------- | ----------------------------------------------------------------------------------- | -------- | --------- | --------- | --------- | ---------- | ---------- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |          |           |           |           |            |            |

### Segmentation

The segmentation benchmarks includes 2 downstream task datasets, **Cityscapes** and **Pascal VOC 2012 + Aug**. It follows the evluation protocols set up by MMSegmentation.

#### Pascal VOC 2012 + Aug

Please refer to [{file name}]() for details of config.

| Model     | Config                                                                              | mIOU |
| --------- | ----------------------------------------------------------------------------------- | ---- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |      |


#### Cityscapes

Please refer to [{file name}]() for details of config.

| Model     | Config                                                                              | mIOU |
| --------- | ----------------------------------------------------------------------------------- | ---- |
| [model]() | [resnet50_8xb32-accum16-coslr-200e](byol_resnet50_8xb32-accum16-coslr-200e_in1k.py) |      |