Warning: Not official code, not achieving promising results yet and somewhat slow

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1. This repo attempts to reproduce Tree-Structured Reinforcement Learning for Sequential Object Localization with pytorch 1.4.0.

   • Requirements(higher or lower versions might also work well)

     • pytorch 1.4.0
     • numpy 1.18.1
     • Prefetch version of DataLoader: IgorSusmelj/pytorch-styleguide#5
     • PIL 7.1.2
     • matplotlib 3.2.1
     • tensorboard 2.1.0

   • Branches

     • main: (Try this first)

       • basic code
       • load images from disk
       • fix ratio to 1:1 and image size to (224, 224)
       • support voc2007 and voc2012 combined dataset: training on 07+12 trainval(~16000 pics), testing on 07 test(~5000 pics)

     • faster:

       • pre-extracted feature map to speed up
       • support loading all feature map to memory
       • keep original ratio and resize longest edge to defined size (eg. 500)
       • support voc2007 only: training on 07 trainval(~5000 pics), testing on 07 test(~5000 pics)

   • Usage

     • training

       • mkdir model_params
       • change settings by set_args() and global variables
       • python train.py

     • evaluating

       • eg. python evaluate.py --model_name debug --model_check_point epoch_x_iter_x.pth.tar
       • result.json will save to ./model_params/debug

     • visualizing

       • eg. python visualize_tree.py --json_path ./model_params/debug/results.json --vis_dir vis --num_images 50
       • ./model_params/debug/vis will be created and stores bbox-tree pictures

     • extracting

       • eg. python preprocess.py --year 2007 --image_set trainval --max_size 500
       • see preprocess.py in branch faster for more details

   • Dataset

     • torchvision.datasets.VOCDetection support downloading VOC2007 and VOC2012 by change download=True
     • Or mkdir data and follow the file structures shown below:

     data
     ├── feature_map_2007_trainval.h5
     ├── img_info_2007_trainval.pkl
     ├── voc2007
     │   └── VOCdevkit
     └── voc2012
         └── VOCdevkit
     

2. Overview of the model and search method from original paper:

   • Tree-RL

     

   • Q-Net: States

     

   • Actions

     

3. Major implementation difference between this repo and original paper: (For the sake of speed)

   • (ResNet50 + average pooling) instead of (VGG16 + flatten) is used in the feature map extractor. see model/encoder.pyfor more details.

   • Only 4 layers of the tree is generated (including the root node) during evaluate searching.

   • Reduce action history in states from 50 to 3.*

   • Reduce maximum searching steps during training from 50 to 15.

     * : In my opinion, since I adopt 4-layer tree which requires only 3 actions search from root to leaf, setting action history to larger size simply adds additional zeros to the input.

4. Results (based on Branch faster)

   • training speed: around 30 minutes per epoch

   • training curves:

     • P/R of test set

     • epsilon / loss / reward: smoothing=0.999

   • examples: from layer 0 to layer 3, blue bboxes are ground truth while red bboxes are predicted by agent modified based on this repo

     

5. Problems(Help wanted!)

   • Huge gap between my implementation and original paper.
   • Loss is really hard to converge.
   • Reward seems improving slowly.
   • Visualization of bbox scaling and moving is not very convincing.
   • Scaled up dataset (07+12) shows little improvement to final performance but achieves 3x training time.