## Installation

### Requirements

- Linux
- Python 3.5+ ([Say goodbye to Python2](https://python3statement.org/))
- PyTorch 1.0+ or PyTorch-nightly
- CUDA 9.0+
- NCCL 2+
- GCC 4.9+
- [mmcv](https://github.com/open-mmlab/mmcv)

We have tested the following versions of OS and softwares:

- OS: Ubuntu 16.04/18.04 and CentOS 7.2
- CUDA: 9.0/9.2/10.0
- NCCL: 2.1.15/2.2.13/2.3.7/2.4.2
- GCC: 4.9/5.3/5.4/7.3

### Install mmdetection

a. Create a conda virtual environment and activate it. Then install Cython.

```shell
conda create -n open-mmlab python=3.7 -y
conda activate open-mmlab

conda install cython
```

b. Install PyTorch stable or nightly and torchvision following the [official instructions](https://pytorch.org/).

c. Clone the mmdetection repository.

```shell
git clone https://github.com/open-mmlab/mmdetection.git
cd mmdetection
```

d. Install mmdetection (other dependencies will be installed automatically).

```shell
python setup.py develop
# or "pip install -v -e ."
```

Note:

1. It is recommended that you run the step e each time you pull some updates from github. If there are some updates of the C/CUDA codes, you also need to run step d.
The git commit id will be written to the version number with step e, e.g. 0.6.0+2e7045c. The version will also be saved in trained models.

2. Following the above instructions, mmdetection is installed on `dev` mode, any modifications to the code will take effect without installing it again.

### Prepare COCO dataset.

It is recommended to symlink the dataset root to `$MMDETECTION/data`.

```
mmdetection
├── mmdet
├── tools
├── configs
├── data
│   ├── coco
│   │   ├── annotations
│   │   ├── train2017
│   │   ├── val2017
│   │   ├── test2017
│   ├── cityscapes
│   │   ├── annotations
│   │   ├── train
│   │   ├── val
│   ├── VOCdevkit
│   │   ├── VOC2007
│   │   ├── VOC2012

```
The cityscapes annotations have to be converted into the coco format using the [cityscapesScripts](https://github.com/mcordts/cityscapesScripts) toolbox.
We plan to provide an easy to use conversion script. For the moment we recommend following the instructions provided in the 
[maskrcnn-benchmark](https://github.com/facebookresearch/maskrcnn-benchmark/tree/master/maskrcnn_benchmark/data) toolbox. When using this script all images have to be moved into the same folder. On linux systems this can e.g. be done for the train images with:
```shell
cd data/cityscapes/
mv train/*/* train/
```

### Scripts
[Here](https://gist.github.com/hellock/bf23cd7348c727d69d48682cb6909047) is
a script for setting up mmdetection with conda.

### Notice
You can run `python(3) setup.py develop` or `pip install -v -e .` to install mmdetection if you want to make modifications to it frequently.

If there are more than one mmdetection on your machine, and you want to use them alternatively.
Please insert the following code to the main file
```python
import os.path as osp
import sys
sys.path.insert(0, osp.join(osp.dirname(osp.abspath(__file__)), '../'))
```
or run the following command in the terminal of corresponding folder.
```shell
export PYTHONPATH=`pwd`:$PYTHONPATH
```