# deep-person-reid
This repo contains [pytorch](http://pytorch.org/) implementations of deep person re-identification approaches.

We will actively maintain this repo.

## Install
1. `cd` to the folder where you want to download this repo.
2. run `git clone https://github.com/KaiyangZhou/deep-person-reid`.

## Prepare data
Create a directory to store reid datasets under this repo via
```
cd deep-person-reid/
mkdir data/
```

Market1501 [7]:
1. download dataset to `data/` from http://www.liangzheng.org/Project/project_reid.html.
2. extract dataset and rename to `market1501`.

MARS [8]:
1. create a directory named `mars/` under `data/`.
2. download dataset to `data/mars/` from http://www.liangzheng.com.cn/Project/project_mars.html.
3. extract `bbox_train.zip` and `bbox_test.zip`.
4. download split information from https://github.com/liangzheng06/MARS-evaluation/tree/master/info and put `info/` in `data/mars`. (we want to follow the standard split in [8])

## Models
* `models/ResNet.py`: ResNet50 [1], ResNet50M [2].
* `models/DenseNet.py`: DenseNet121 [3].

## Train
Training codes are implemented in
* `train_img_model_xent.py`: train image model with cross entropy loss.
* `train_img_model_xent_htri.py`: train image model with combination of cross entropy loss and hard triplet loss.
* `train_vid_model_xent.py`: train video model with cross entropy loss.
* `train_vid_model_xent_htri.py`: train video model with combination of cross entropy loss and hard triplet loss.

For example, to train an image reid model using ResNet50 and cross entropy loss, run
```
python train_img_model_xent.py -d market1501 -a resnet50 --max-epoch 60 --train-batch 32 --test-batch 32 --stepsize 20 --eval-step 20 --save-dir log/resnet50 --gpu-devices 0
```

## Results
### Setup
* Image size: 256-by-128 <br />
* Batch: 32 <br />
* Optimizer: Adam [6] <br />
* Loss functions: <br />
xent: cross entropy + label smoothing regularizer [5] <br />
htri: triplet loss with hard positive/negative mining [4] <br />

### Image person reid
#### Market1501

| Model | Size (M) | Loss | Rank-1/5/10 (%) | mAP (%) | Model weights | Reported Rank | Reported mAP |
| --- | :---: | :---: | :---: | :---: | :---: | :---: | :---: |
| ResNet50 | 25.05 | xent | 85.4/94.1/95.9 | 68.8 | [download](http://www.eecs.qmul.ac.uk/~kz303/deep-person-reid/model-zoo/resnet50_xent_market1501.pth.tar) | | |
| DenseNet121 | 7.72 | xent | 86.5/93.6/95.7 | 67.8 | [download](http://www.eecs.qmul.ac.uk/~kz303/deep-person-reid/model-zoo/densenet121_xent_market1501.pth.tar) | | |
| ResNet50M | 30.01 | xent | | | [download]() | 89.9/-/- | 75.6 |

### Video person reid
#### MARS

### Test
Say you have downloaded ResNet50 trained with `xent` on `market1501`. The path to this model is  `'saved-models/resnet50-xent-market1501.pth.tar'` (create a directory to store model weights `mkdir saved-models/`). Then, run the following command to test
```
python train_img_model_xent.py -d market1501 -a resnet50 --evaluate --resume saved-models/resnet50_xent_market1501.pth.tar
```

## References
[1] [He et al. Deep Residual Learning for Image Recognition. CVPR 2016.](https://arxiv.org/abs/1512.03385)<br />
[2] [Yu et al. The Devil is in the Middle: Exploiting Mid-level Representations for Cross-Domain Instance Matching. arXiv:1711.08106.](https://arxiv.org/abs/1711.08106) <br />
[3] [Huang et al. Densely Connected Convolutional Networks. CVPR 2017.](https://arxiv.org/abs/1608.06993) <br />
[4] [Hermans et al. In Defense of the Triplet Loss for Person Re-Identification. arXiv:1703.07737.](https://arxiv.org/abs/1703.07737) <br />
[5] [Szegedy et al. Rethinking the Inception Architecture for Computer Vision. CVPR 2016.](https://arxiv.org/abs/1512.00567) <br />
[6] [Kingma and Ba. Adam: A Method for Stochastic Optimization. ICLR 2015.](https://arxiv.org/abs/1412.6980) <br />
[7] [Zheng et al. Scalable Person Re-identification: A Benchmark. ICCV 2015.](https://www.cv-foundation.org/openaccess/content_iccv_2015/papers/Zheng_Scalable_Person_Re-Identification_ICCV_2015_paper.pdf) <br />
[8] [Zheng et al. MARS: A Video Benchmark for Large-Scale Person Re-identification. ECCV 2016.](http://www.liangzheng.com.cn/Project/project_mars.html) <br />