SimpleDet - A Simple and Versatile Framework for Object Detection and Instance Recognition

Major Features

• FP16 training for memory saving and up to 2.5X acceleration
• Highly scalable distributed training available out of box
• Full coverage of state-of-the-art models including FasterRCNN, MaskRCNN, CascadeRCNN, RetinaNet and TridentNet
• Extensive feature set including large batch BN, deformable convolution, soft NMS, multi-scale train/test
• Modular design for coding-free exploration of new experiment settings

Setup

Install

SimpleDet contains a lot of C++ operators not in MXNet offical repo, so one has to build MXNet from scratch. Please refer to INSTALL.md more details

Preparing Data

SimpleDet requires groundtruth annotation organized as following format

[
    {
        "gt_class": (nBox, ),
        "gt_bbox": (nBox, 4),
        "flipped": bool,
        "h": int,
        "w": int,
        "image_url": str,
        "im_id": int,
        
        # this fields are generated on the fly during test
        "rec_id": int,
        "resize_h": int,
        "resize_w": int,
        ...
    },
    ...
]

Especially, for experimenting on coco datatet, one can organize coco data in

data/
    coco/
        annotations/
            instances_train2014.json
            instances_valminusminival2014.json
            instances_minival2014.json
            image_info_test-dev2017.json
        images/
            train2014
            val2014
            test2017

and run the helper script to generate roidb

python3 utils/generate_roidb.py --dataset coco --dataset-split train2014
python3 utils/generate_roidb.py --dataset coco --dataset-split valminusminival2014
python3 utils/generate_roidb.py --dataset coco --dataset-split minival2014
python3 utils/generate_roidb.py --dataset coco --dataset-split test-dev2017

Deploy dependency and compile extension

1. setup mxnext, a wrapper of mxnet symbolic API

git clone https://github.com/RogerChern/mxnext

2. run make in simpledet directory to install cython extensions

Quick Start

# train
python3 detection_train.py --config config/detection_config.py

# test
python3 detection_test.py --config config/detection_config.py

Project Design

Model Zoo

Please refer to MODEL_ZOO.md for available models

Code Structure

detection_train.py
detection_test.py
config/
    detection_config.py
core/
    detection_input.py
    detection_metric.py
    detection_module.py
models/
    FPN/
    tridentnet/
    maskrcnn/
    cascade_rcnn/
    retinanet/
mxnext/
symbol/
    builder.py

Config

Everything is configurable from the config file, all the changes should be out of source.

Experiments

One experiment is a directory in experiments folder with the same name as the config file.

E.g. r50_fixbn_1x.py is the name of a config file

config/
    r50_fixbn_1x.py
experiments/
    r50_fixbn_1x/
        checkpoint.params
        log.txt
        coco_minival2014_result.json

Models

The models directory contains SOTA models implemented in SimpletDet.

How is Faster-RCNN built

Simpledet supports many popular detection methods and here we take Faster-RCNN as a typical example to show how a detector is built.

• Preprocessing. The preprocessing methods of the detector is implemented through DetectionAugmentation.
  • Image/bbox-related preprocessing, such as Norm2DImage and Resize2DImageBbox.
  • Anchor generator AnchorTarget2D, which generates anchors and corresponding anchor targets for training RPN.
• Network Structure. The training and testing symbols of Faster-RCNN detector is defined in FasterRcnn. The key components are listed as follow:
  • Backbone. Backbone provides interfaces to build backbone networks, e.g. ResNet and ResNext.
  • Neck. Neck provides interfaces to build complementary feature extraction layers for backbone networks, e.g. FPNConvTopDown builds Top-down pathway for Feature Pyramid Network.
  • RPN head. RpnHead aims to build classification and regression layers to generate proposal outputs for RPN. Meanwhile, it also provides interplace to generate sampled proposals for the subsequent R-CNN.
  • Roi Extractor. RoiExtractor extracts features for each roi (proposal) based on the R-CNN features generated by Backbone and Neck.
  • Bounding Box Head. BboxHead builds the R-CNN layers for proposal refinement.

How to build a custom detector

The flexibility of simpledet framework makes it easy to build different detectors. We take TridentNet as an example to demonstrate how to build a custom detector simply based on the Faster-RCNN framework.

• Preprocessing. The additional processing methods could be provided accordingly by inheriting from DetectionAugmentation.
  • In TridentNet, a new TridentAnchorTarget2D is implemented to generate anchors for multiple branches and filter anchors for scale-aware training scheme.
• Network Structure. The new network structure could be constructed easily for a custom detector by modifying some required components as needed and
  • For TridentNet, we build trident blocks in the Backbone according to the descriptions in the paper. We also provide a TridentRpnHead to generate filtered proposals in RPN to implement the scale-aware scheme. Other components are shared the same with original Faster-RCNN.

Distributed Training

Please refer to DISTRIBUTED.md

Contributors

Yuntao Chen, Chenxia Han, Yanghao Li, Zehao Huang, Yi Jiang, Naiyan Wang

License

This project is release under the Apache 2.0 license for non-commercial usage. For commercial usage, please contact us for another license.