Knowledge Distillation as Efficient Pretraining: Faster Convergence, Higher Data-efficiency, and Better Transferability

This repository contains the code and models necessary to replicate the results of our paper:

@inproceedings{he2022knowledge,
  title={Knowledge Distillation as Efficient Pre-training: Faster Convergence, Higher Data-efficiency, and Better Transferability
},
  author={He, Ruifei and Sun, Shuyang, and Yang, Jihan, and Bai, Song and Qi, Xiaojuan},
  booktitle={Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition},
  year={2022}
}

Abstract

Large-scale pre-training has been proven to be crucial for various computer vision tasks. However, with the increase of pre-training data amount, model architecture amount, and the private/inaccessible data, it is not very efficient or possible to pre-train all the model architectures on large-scale datasets. In this work, we investigate an alternative strategy for pre-training, namely Knowledge Distillation as Efficient Pre-training (KDEP), aiming to efficiently transfer the learned feature representation from existing pre-trained models to new student models for future downstream tasks. We observe that existing Knowledge Distillation (KD) methods are unsuitable towards pre-training since they normally distill the logits that are going to be discarded when transferred to downstream tasks. To resolve this problem, we propose a feature-based KD method with non-parametric feature dimension aligning. Notably, our method performs comparably with supervised pre-training counterparts in 3 downstream tasks and 9 downstream datasets requiring 10x less data and 5x less pre-training time.

Getting started

1. Clone our repo: git clone https://github.com/CVMI-Lab/KDEP.git

2. Install dependencies:

   conda create -n KDEP python=3.7
   conda activate KDEP
   pip install -r requirements.txt
   

Data preparation

• ImageNet-1K (Download)
• Caltech256 (Download)
• Cifar100 (Automatically downloaded when you run the code)
• DTD (Download)
• CUB-200 (Download)
• Cityscapes (Download)
• VOC (segmentation and detection, Download)
• ADE20K (Download)
• COCO (Download)

For image classification datasets (except for Caltech256), the folder structure should follow ImageNet:

data root
├─ train/
  ├── n01440764
  │   ├── n01440764_10026.JPEG
  │   ├── n01440764_10027.JPEG
  │   ├── ......
  ├── ......
├─ val/
  ├── n01440764
  │   ├── ILSVRC2012_val_00000293.JPEG
  │   ├── ILSVRC2012_val_00002138.JPEG
  │   ├── ......
  ├── ......

For semantic segmentation datasets, please refer to PyTorch Semantic Segmentation.

For object detection datasets, please refer to Detectron2.

Pre-training with KDEP

1. Download teacher models (Download), and put them under pretrained-models/ .

2. You can use a provided python file scripts/make-imgnet-subset.py to create the 10% of ImageNet-1K data.

3. Update the path of the dataset for KDEP (10% or 100% of ImageNet-1K) in src/utils/constants.py.

4. Prepare the SVD weights for teacher models. You can download the weights we provide (Download) or generate using our provided script scripts/gen_svd_weights.sh .

   sh scripts/gen_svd_weights.sh imgnet_128k ex_gen_svd 0
   

5. Scripts of pre-training with KDEP are in scripts/. For example, you can use teacher-student pair of Microsoft ResNet50 -> ResNet18 with scripts/KDEP_MS-R50_R18.sh by:

   sh scripts/KDEP_MS-R50_R18.sh imgnet_128k exp_name 90 30 5e-4 0,1,2,3
   ### imgnet_128k or imgnet_full to select 10% or 100% ImageNet-1K data
   ### 90 is #epoch, 30 is step-lr
   ### 5e-4 is weight decay
   ### 0,1,2,3 is GPU id
   

   You can run KDEP with different data amount and training schedules by changing the data name (imgnet_128k or imgnet_full), #epoch and step-lr, and weight decay.

   Note that we do not generate the svd weights for 100% ImageNet-1K data, but directly use the svd weights generated from 10% data.

Transfer learning experiments

Image classification

1. We use four image classification tasks: CIFAR100, DTD, Caltech256, CUB-200.

2. Scripts (scripts/TL_img-cls_R18.sh and scripts/TL_img-cls_mnv2.sh ) are provided for running all four tasks twice for a distilled student (R18/mnv2).

   sh scripts/TL_img-cls_R18.sh exp_name
   # note the exp_name here should be identical to that of the distilled student
   

Semantic segmentation

1. We use three semantic segmentation tasks: Cityscapes, VOC2012, ADE20K.

2. Transform the checkpoint into segmentation code format by src/transform_ckpt_custom2seg.py

   cd src
   python3 transform_ckpt_custom2seg.py exp_name
   # note the exp_name here should be identical to that of the distilled student
   

   Move the transformed checkpoint to semseg/initmodel/.

3. Scripts (semseg/tool/TL_seg_R18.sh and semseg/tool/TL_seg_mnv2.sh ) are provided for running all three tasks twice for a distilled student (R18/mnv2).

   cd semseg
   sh tool/TL_seg_R18.sh ckpt_name
   # note the ckpt_name should be what you put into the semseg/initmodel/ in step1.
   

Object detection

1. We use two object detection tasks: COCO and VOC.

2. Transform the checkpoint into Detectron2 format by src/transform_ckpt_custom2det.py

   cd src
   python3 transform_ckpt_custom2det.py exp_name R18
   # note the exp_name here should be identical to that of the distilled student
   # R18 could be changed to mnv2
   

   Move the transformed checkpoint to detectron2/ckpts/ .

3. Install Detectron2, and export dataset path

   python3 -m pip install -e detectron2
   export DETECTRON2_DATASETS='path/to/datasets'
   

4. Scripts (detectron2/tool/TL_det_R18.sh and detectron2/tool/TL_det_mnv2.sh ) are provided for running all two tasks twice for a distilled student (R18/mnv2).

   cd detectron2/tool
   sh TL_det_R18.sh ckpt_name
   # note the ckpt_name should be what you put into the semseg/initmodel/ in step1.
   

Distilled models of KDEP

We provide some distilled models of KDEP here.

1. (Download) ResNet18, KDEP(SVD+PTS) from MS-R50 teacher on 100% ImageNet-1K data for 90 epochs.
2. (Download) MobileNet-V2, KDEP(SVD+PTS) from MS-R50 teacher on 100% ImageNet-1K data for 90 epochs.

Acknowledgement

Our code is mainly based on robust-models-transfer, we also thank the open source code from PyTorch Semantic Segmentation and Detectron2.