GETTING_STARTED.md

# Getting Started

For setting up the running environment, please refer to [installation
instructions](INSTALL.md).


## Training

#### Single-GPU Training


```bash
export CUDA_VISIBLE_DEVICES=0
export PYTHONPATH=$PYTHONPATH:.
python tools/train.py -c configs/faster_rcnn_r50_1x.yml
```

#### Multi-GPU Training

```bash
export CUDA_VISIBLE_DEVICES=0,1,2,3,4,5,6,7
export PYTHONPATH=$PYTHONPATH:.
python tools/train.py -c configs/faster_rcnn_r50_1x.yml
```

#### CPU Training

```bash
export CPU_NUM=8
export PYTHONPATH=$PYTHONPATH:.
python tools/train.py -c configs/faster_rcnn_r50_1x.yml -o use_gpu=false
```

##### Optional arguments

- `-r` or `--resume_checkpoint`: Checkpoint path for resuming training. Such as: `-r output/faster_rcnn_r50_1x/10000`
- `--eval`: Whether to perform evaluation in training, default is `False`
- `--output_eval`: If perform evaluation in training, this edits evaluation directory, default is current directory.
- `-d` or `--dataset_dir`: Dataset path, same as `dataset_dir` of configs. Such as: `-d dataset/coco`
- `-c`: Select config file and all files are saved in `configs/`
- `-o`: Set configuration options in config file. Such as: `-o max_iters=180000`. `-o` has higher priority to file configured by `-c`
- `--use_tb`: Whether to record the data with [tb-paddle](https://github.com/linshuliang/tb-paddle), so as to display in Tensorboard, default is `False`
- `--tb_log_dir`: tb-paddle logging directory for scalar, default is `tb_log_dir/scalar`
- `--fp16`: Whether to enable mixed precision training (requires GPU), default is `False`
- `--loss_scale`: Loss scaling factor for mixed precision training, default is `8.0`


##### Examples

- Perform evaluation in training
```bash
export CUDA_VISIBLE_DEVICES=0,1,2,3,4,5,6,7
export PYTHONPATH=$PYTHONPATH:.
python -u tools/train.py -c configs/faster_rcnn_r50_1x.yml --eval
```

Alternating between training epoch and evaluation run is possible, simply pass
in `--eval` to do so and evaluate at each snapshot_iter. It can be modified at `snapshot_iter` of the configuration file. If evaluation dataset is large and
causes time-consuming in training, we suggest decreasing evaluation times or evaluating after training. When perform evaluation in training,
the best model with highest MAP is saved at each `snapshot_iter`. `best_model` has the same path as `model_final`.


- Configure dataset path
```bash
export CUDA_VISIBLE_DEVICES=0,1,2,3,4,5,6,7
export PYTHONPATH=$PYTHONPATH:.
python -u tools/train.py -c configs/faster_rcnn_r50_1x.yml \
                         -d dataset/coco
```

- Fine-tune other task

When using pre-trained model to fine-tune other task, two methods can be used:

1. The excluded pre-trained parameters can be set by `finetune_exclude_pretrained_params` in YAML config
2. Set -o finetune_exclude_pretrained_params in the arguments.

```bash
export CUDA_VISIBLE_DEVICES=0,1,2,3,4,5,6,7
export PYTHONPATH=$PYTHONPATH:.
python -u tools/train.py -c configs/faster_rcnn_r50_1x.yml \
                         -o pretrain_weights=output/faster_rcnn_r50_1x/model_final/ \
                            finetune_exclude_pretrained_params = ['cls_score','bbox_pred']
```

- Mixed Precision Training

Mixed precision training can be enabled with `--fp16` flag. Currently Faster-FPN, Mask-FPN and Yolov3 have been verified to be working with little to no loss of precision (less than 0.2 mAP)

To speed up mixed precision training, it is recommended to train in multi-process mode, for example

```bash
export PYTHONPATH=$PYTHONPATH:.
python -m paddle.distributed.launch --selected_gpus 0,1,2,3,4,5,6,7 tools/train.py --fp16 -c configs/faster_rcnn_r50_fpn_1x.yml
```

If loss becomes `NaN` during training, try tweak the `--loss_scale` value. Please refer to the Nvidia [documentation](https://docs.nvidia.com/deeplearning/sdk/mixed-precision-training/index.html#mptrain) on mixed precision training for details.

Also, please note mixed precision training currently requires changing `norm_type` from `affine_channel` to `bn`.


##### NOTES

- `CUDA_VISIBLE_DEVICES` can specify different gpu numbers. Such as: `export CUDA_VISIBLE_DEVICES=0,1,2,3`. GPU calculation rules can refer [FAQ](#faq)
- Dataset is stored in `dataset/coco` by default (configurable).
- Dataset will be downloaded automatically and cached in `~/.cache/paddle/dataset` if not be found locally.
- Pretrained model is downloaded automatically and cached in `~/.cache/paddle/weights`.
- Model checkpoints are saved in `output` by default (configurable).
- When finetuning, users could set `pretrain_weights` to the models published by PaddlePaddle. Parameters matched by fields in finetune_exclude_pretrained_params will be ignored in loading and fields can be wildcard matching. For detailed information, please refer to [Transfer Learning](TRANSFER_LEARNING.md).
- To check out hyper parameters used, please refer to the [configs](../configs).
- RCNN models training on CPU is not supported on PaddlePaddle<=1.5.1 and will be fixed on later version.



## Evaluation

```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python tools/eval.py -c configs/faster_rcnn_r50_1x.yml
```

#### Optional arguments

- `-d` or `--dataset_dir`: Dataset path, same as dataset_dir of configs. Such as: `-d dataset/coco`
- `--output_eval`: Evaluation directory, default is current directory.
- `-o`: Set configuration options in config file. Such as: `-o weights=output/faster_rcnn_r50_1x/model_final`
- `--json_eval`: Whether to eval with already existed bbox.json or mask.json. Default is `False`. Json file directory is assigned by `-f` argument.

#### Examples

- Evaluate by specified weights path and dataset path
```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python -u tools/eval.py -c configs/faster_rcnn_r50_1x.yml \
                        -o weights=output/faster_rcnn_r50_1x/model_final \
                        -d dataset/coco
```

- Evaluate with json
```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python tools/eval.py -c configs/faster_rcnn_r50_1x.yml \
             --json_eval \
             -f evaluation/
```

The json file must be named bbox.json or mask.json, placed in the `evaluation/` directory. Or without the `-f` parameter, default is the current directory.

#### NOTES

- Checkpoint is loaded from `output` by default (configurable)
- Multi-GPU evaluation for R-CNN and SSD models is not supported at the
moment, but it is a planned feature


## Inference


- Run inference on a single image:

```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python tools/infer.py -c configs/faster_rcnn_r50_1x.yml --infer_img=demo/000000570688.jpg
```

- Multi-image inference:

```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python tools/infer.py -c configs/faster_rcnn_r50_1x.yml --infer_dir=demo
```

#### Optional arguments

- `--output_dir`: Directory for storing the output visualization files.
- `--draw_threshold`: Threshold to reserve the result for visualization. Default is 0.5.
- `--save_inference_model`: Save inference model in output_dir if True.
- `--use_tb`: Whether to record the data with [tb-paddle](https://github.com/linshuliang/tb-paddle), so as to display in Tensorboard, default is `False`
- `--tb_log_dir`: tb-paddle logging directory for image, default is `tb_log_dir/image`

#### Examples

- Output specified directory && Set up threshold

```bash
# run on GPU with:
export PYTHONPATH=$PYTHONPATH:.
export CUDA_VISIBLE_DEVICES=0
python tools/infer.py -c configs/faster_rcnn_r50_1x.yml \
                      --infer_img=demo/000000570688.jpg \
                      --output_dir=infer_output/ \
                      --draw_threshold=0.5 \
                      -o weights=output/faster_rcnn_r50_1x/model_final \
                      --use_tb=Ture
```

The visualization files are saved in `output` by default, to specify a different path, simply add a `--output_dir=` flag.
`--draw_threshold` is an optional argument. Default is 0.5.
Different thresholds will produce different results depending on the calculation of [NMS](https://ieeexplore.ieee.org/document/1699659).
If users want to infer according to customized model path, `-o weights` can be set for specified path.
`--use_tb` is an optional argument, if `--use_tb` is `True`, the tb-paddle will record data in directory,
so users can see the results in Tensorboard.

- Save inference model

```bash
# run on GPU with:
export CUDA_VISIBLE_DEVICES=0
export PYTHONPATH=$PYTHONPATH:.
python tools/infer.py -c configs/faster_rcnn_r50_1x.yml \
                      --infer_img=demo/000000570688.jpg \
                      --save_inference_model
```

Save inference model by set `--save_inference_model`, which can be loaded by PaddlePaddle predict library.


## FAQ

**Q:**  Why do I get `NaN` loss values during single GPU training? </br>
**A:**  The default learning rate is tuned to multi-GPU training (8x GPUs), it must
be adapted for single GPU training accordingly (e.g., divide by 8).
The calculation rules are as follows，they are equivalent: </br>


| GPU number  | Learning rate  | Max_iters | Milestones       |
| :---------: | :------------: | :-------: | :--------------: |
| 2           | 0.0025         | 720000    | [480000, 640000] |
| 4           | 0.005          | 360000    | [240000, 320000] |
| 8           | 0.01           | 180000    | [120000, 160000] |


**Q:**  How to reduce GPU memory usage? </br>
**A:**  Setting environment variable FLAGS_conv_workspace_size_limit to a smaller
number can reduce GPU memory footprint without affecting training speed.
Take Mask-RCNN (R50) as example, by setting `export FLAGS_conv_workspace_size_limit=512`,
batch size could reach 4 per GPU (Tesla V100 16GB).


**Q:**  How to change data preprocessing? </br>
**A:**  Set `sample_transform` in configuration. Note that **the whole transforms** need to be added in configuration.
For example, `DecodeImage`, `NormalizeImage` and `Permute` in RCNN models. For detail description, please refer
to [config_example](config_example).