Robust Re-Identification by Multiple Views Knowledge Distillation

This repository contains Pytorch code for the ECCV20 paper "Robust Re-Identification by Multiple Views Knowledge Distillation" [arXiv]

VKD - Overview

@inproceedings{porrello2020robust,    
    title={Robust Re-Identification by Multiple Views Knowledge Distillation},
    author={Porrello, Angelo and Bergamini, Luca and Calderara, Simone},
    booktitle={European Conference on Computer Vision},
    pages={93--110},
    year={2020},
    organization={Springer}
}

Installation Note

Tested with Python3.6.8 on Ubuntu (17.04, 18.04).

Setup an empty pip environment
Install packages using pip install -r requirements.txt
Install torch1.3.1 using pip install torch==1.3.1+cu92 torchvision==0.4.2+cu92 -f https://download.pytorch.org/whl/torch_stable.html
Place datasets in .datasets/ (Please note you may need do request some of them to their respective authors)
Run scripts from commands.txt

Please note that if you're running the code from Pycharm (or another IDE) you may need to manually set the working path to PROJECT_PATH

VKD Training (MARS [1])

Data preparation

Create the folder ./datasets/mars
Download the dataset from here
Unzip data and place the two folders inside the MARS [1] folder
Download metadata from here
Place them in a folder named info under the same path
You should end up with the following structure:

PROJECT_PATH/datasets/mars/
|-- bbox_train/
|-- bbox_test/
|-- info/

Teacher-Student Training

First step: the backbone network is trained for the standard Video-To-Video setting. In this stage, each training example comprises of N images drawn from the same tracklet (N=8 by default; you can change it through the argument --num_train_images.

# To train ResNet-50 on MARS (teacher, first step) run:
python ./tools/train_v2v.py mars --backbone resnet50 --num_train_images 8 --p 8 --k 4 --exp_name base_mars_resnet50 --first_milestone 100 --step_milestone 100

Second step: we appoint it as the teacher and freeze its parameters. Then, a new network with the role of the student is instantiated. In doing so, we feed N views (i.e. images captured from multiple cameras) as input to the teacher and ask the student to mimic the same outputs from fewer (M=2 by default,--num_student_images) frames.

# To train a ResVKD-50 (student) run:
python ./tools/train_distill.py mars ./logs/base_mars_resnet50 --exp_name distill_mars_resnet50 --p 12 --k 4 --step_milestone 150 --num_epochs 500

Model Zoo

We provide a bunch of pre-trained checkpoints through two zip files (baseline.zip containing the weights of the teacher networks, distilled.zip the student ones). Therefore, to evaluate ResNet-50 and ResVKD-50 on MARS, proceed as follows:

Download baseline.zip from here and distilled.zip from here (~4.8 GB)
Unzip the two folders inside the PROJECT_PATH/logs folder
Then, you can evaluate both networks using the eval.py script:

python ./tools/eval.py mars ./logs/baseline_public/mars/base_mars_resnet50 --trinet_chk_name chk_end

python ./tools/eval.py mars ./logs/distilled_public/mars/selfdistill/distill_mars_resnet50 --trinet_chk_name chk_di_1

You should end up with the following results on MARS (see Tab.1 of the paper for VeRi-776 and Duke-Video-ReID):

Backbone	top1 I2V	mAP I2V	top1 V2V	mAP V2V
`ResNet-34`	80.81	70.74	86.67	78.03
`ResVKD-34`	82.17	73.68	87.83	79.50
`ResNet-50`	82.22	73.38	87.88	81.13
`ResVKD-50`	83.89	77.27	88.74	82.22
`ResNet-101`	82.78	74.94	88.59	81.66
`ResVKD-101`	85.91	77.64	89.60	82.65

Backbone	top1 I2V	mAP I2V	top1 V2V	mAP V2V
`ResNet-50bam`	82.58	74.11	88.54	81.19
`ResVKD-50bam`	84.34	78.13	89.39	83.07

Backbone	top1 I2V	mAP I2V	top1 V2V	mAP V2V
`DenseNet-121`	82.68	74.34	89.75	81.93
`DenseVKD-121`	84.04	77.09	89.80	82.84

Backbone	top1 I2V	mAP I2V	top1 V2V	mAP V2V
`MobileNet-V2`	78.64	67.94	85.96	77.10
`MobileVKD-V2`	83.33	73.95	88.13	79.62

Teacher-Student Explanations

As discussed in the main paper, we have leveraged GradCam [2] to highlight the input regions that have been considered paramount for predicting the identity. We have performed the same analysis for the teacher network as well as for the student one: as can be seen, the latter pays more attention to the subject of interest compared to its teacher.

Model Explanation

You can draw the heatmaps with the following command:

python -u ./tools/save_heatmaps.py mars <path-to-teacher-net> --chk_net1 <teacher-checkpoint-name> <path-to-student-net> --chk_net2 <student-checkpoint-name> --dest_path <output-dir>

References

Zheng, L., Bie, Z., Sun, Y., Wang, J., Su, C., Wang, S., Tian, Q.: Mars: A video benchmark for large-scale person re-identification. In: European Conference on Computer Vision (2016)
Selvaraju, R. R., Cogswell, M., Das, A., Vedantam, R., Parikh, D., & Batra, D. (2017). Grad-cam: Visual explanations from deep networks via gradient-based localization. In Proceedings of the IEEE international conference on computer vision (pp. 618-626).

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