lightning-hydra-template/README.md

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# Lightning-Hydra-Template

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A clean and scalable template to kickstart your deep learning project 🚀⚡🔥<br>
Click on [<kbd>Use this template</kbd>](https://github.com/ashleve/lightning-hydra-template/generate) to initialize new repository.

*Currently uses dev version of Hydra.<br>Suggestions are always welcome!*

</div>
<br><br>

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## Introduction
This template tries to be as general as possible - you can easily delete any unwanted features from the pipeline or rewire the configuration, by modifying behavior in [src/train.py](src/train.py).

> Effective usage of this template requires learning of a couple of technologies: [PyTorch](https://pytorch.org), [PyTorch Lightning](https://www.pytorchlightning.ai) and [Hydra](https://hydra.cc). Knowledge of some experiment logging framework like [Weights&Biases](https://wandb.com), [Neptune](https://neptune.ai) or [MLFlow](https://mlflow.org) is also recommended.

**Why you should use it:** it allows you to rapidly iterate over new models/datasets and scale your projects from small single experiments to hyperparameter searches on computing clusters, without writing any boilerplate code. To my knowledge, it's one of the most convenient all-in-one technology stack for Deep Learning research. Good starting point for reproducing papers or kaggle competitions. It's also a collection of best practices for efficient workflow and reproducibility.

**Why you shouldn't use it:** Lightning and Hydra are not yet mature, which means you might run into some bugs sooner or later. Also, even though Lightning is very flexible, it's not well suited for every possible deep learning task.

### Why PyTorch Lightning?
[PyTorch Lightning](https://github.com/PyTorchLightning/pytorch-lightning) is a lightweight PyTorch wrapper for high-performance AI research.
It makes your code neatly organized and provides lots of useful features, like ability to run model on CPU, GPU, multi-GPU cluster and TPU.


### Why Hydra?
[Hydra](https://github.com/facebookresearch/hydra) is an open-source Python framework that simplifies the development of research and other complex applications. The key feature is the ability to dynamically create a hierarchical configuration by composition and override it through config files and the command line. It  allows you to conveniently manage experiments and provides many useful plugins, like [Optuna Sweeper](https://hydra.cc/docs/next/plugins/optuna_sweeper) for hyperparameter search, or [Ray Launcher](https://hydra.cc/docs/next/plugins/ray_launcher) for running jobs on a cluster.
<br>
<br>
<br>


## Main Ideas Of This Template
- **Predefined Structure**: clean and scalable so that work can easily be extended and replicated (see [#Project Structure](#project-structure))
- **Rapid Experimentation**: thanks to automating pipeline with config files and hydra command line superpowers
- **Little Boilerplate**: so pipeline can be easily modified (see [src/train.py](src/train.py))
- **Main Configuration**: main config file specifies default training configuration (see [#Main Project Configuration](#main-project-configuration))
- **Experiment Configurations**: stored in a separate folder, they can be composed out of smaller configs, override chosen parameters or define everything from scratch (see [#Experiment Configuration](#experiment-configuration))
- **Experiment Tracking**: many logging frameworks can be easily integrated! (see [#Experiment Tracking](#experiment-tracking))
- **Logs**: all logs (checkpoints, data from loggers, chosen hparams, etc.) are stored in a convenient folder structure imposed by Hydra (see [#Logs](#logs))
- **Hyperparameter Search**: made easier with Hydra built in plugins like [Optuna Sweeper](https://hydra.cc/docs/next/plugins/optuna_sweeper)
- **Best Practices**: a couple of recommended tools, practices and standards for efficient workflow and reproducibility (see [#Best Practices](#best-practices))
- **Extra Features**: optional utilities to make your life easier (see [#Extra Features](#extra-features))
- **Workflow**: comes down to 4 simple steps (see [#Workflow](#workflow))
<br>


## Project Structure
The directory structure of new project looks like this:
```
├── configs                 <- Hydra configuration files
│   ├── callbacks               <- Callbacks configs
│   ├── datamodule              <- Datamodule configs
│   ├── experiment              <- Experiment configs
│   ├── hparams_search          <- Hyperparameter search configs
│   ├── logger                  <- Logger configs
│   ├── model                   <- Model configs
│   ├── trainer                 <- Trainer configs
│   │
│   └── config.yaml             <- Main project configuration file
│
├── data                    <- Project data
│
├── logs                    <- Logs generated by Hydra and PyTorch Lightning loggers
│
├── notebooks               <- Jupyter notebooks. Naming convention is a number (for ordering),
│                              the creator's initials, and a short `-` delimited description, e.g.
│                              `1.0-jqp-initial-data-exploration.ipynb`.
│
├── tests                   <- Tests of any kind
│
├── src
│   ├── callbacks               <- Lightning callbacks
│   ├── datamodules             <- Lightning datamodules
│   ├── models                  <- Lightning models
│   ├── utils                   <- Utility scripts
│   │   ├── inference_example.py    <- Example of inference with trained model
│   │   └── template_utils.py       <- Extra features for the template
│   │
│   └── train.py                <- Training pipeline
│
├── run.py                  <- Run any pipeline with chosen experiment configuration
│
├── .env.template           <- Template of file for storing private environment variables
├── .autoenv.template       <- Template of file for automatic virtual environment setup
├── .gitignore              <- List of files/folders ignored by git
├── .pre-commit-config.yaml <- Configuration of automatic code formatting
├── conda_env_gpu.yaml      <- File for installing conda environment
├── requirements.txt        <- File for installing python dependencies
├── LICENSE
└── README.md
```
<br>


## 🚀&nbsp; Quickstart
```yaml
# clone project
git clone https://github.com/ashleve/lightning-hydra-template
cd lightning-hydra-template

# [OPTIONAL] create conda environment
conda env create -f conda_env_gpu.yaml -n myenv
conda activate myenv

# install requirements
pip install -r requirements.txt
```

Template contains example with MNIST classification.<br>
When running `python run.py` you should see something like this:
<div align="center">

![](https://github.com/ashleve/lightning-hydra-template/blob/resources/terminal.png)

</div>

### ⚡&nbsp; Your Superpowers
(click to expand)

<details>
<summary><b>Override any config parameter from command line</b></summary>

> Hydra allows you to easily overwrite any parameter defined in your config.
```yaml
python run.py trainer.max_epochs=20 optimizer.lr=1e-4
```
> You can also add new parameters with `+` sign.
```yaml
python run.py +model.new_param="uwu"

```

</details>


<details>
<summary><b>Train on CPU, GPU, TPU or even with DDP and mixed precision</b></summary>

> PyTorch Lightning makes it easy to train your models on different hardware.
```yaml
# train on CPU
python run.py trainer.gpus=0

# train on 1 GPU
python run.py trainer.gpus=1

# train on TPU
python run.py +trainer.tpu_cores=8

# train with DDP (Distributed Data Parallel) (4 GPUs)
python run.py trainer.gpus=4 +trainer.accelerator='ddp'

# train with DDP (Distributed Data Parallel) (8 GPUs, 2 nodes)
python run.py trainer.gpus=4 +trainer.num_nodes=2 +trainer.accelerator='ddp'

# train with mixed precision
python run.py trainer.gpus=1 +trainer.amp_backend="apex" +trainer.precision=16 \
+trainer.amp_level="O2"
```

</details>


<details>
  <summary><b>Train model with any logger available in PyTorch Lightning, like Weights&Biases</b></summary>

> PyTorch Lightning provides convenient integrations with most popular logging frameworks. Read more [here](#experiment-tracking). Using wandb requires you to [setup account](https://www.wandb.com/) first. After that just complete the config as below.<br>
**Click [here](https://wandb.ai/hobglob/template-dashboard/) to see example wandb dashboard generated with this template.**
```yaml
# set project and entity names in `configs/logger/wandb`
wandb:
    project: "your_project_name"
    entity: "your_wandb_team_name"
```

```yaml
# train model with Weights&Biases
# link to wandb dashboard should appear in the terminal
python run.py logger=wandb
```

</details>


<details>
<summary><b>Train model with chosen experiment config</b></summary>

> Experiment configurations are placed in [configs/experiment/](configs/experiment/).
```yaml
python run.py experiment=exp_example_simple
```

</details>


<details>
<summary><b>Attach some callbacks to run</b></summary>

> Callbacks can be used for things such as as model checkpointing, early stopping and [many more](https://pytorch-lightning.readthedocs.io/en/latest/extensions/callbacks.html#built-in-callbacks).<br>
Callbacks configurations are placed in [configs/callbacks/](configs/callbacks/).
```yaml
python run.py callbacks=default_callbacks
```

</details>


<details>
<summary><b>Use different tricks available in Pytorch Lightning</b></summary>

> PyTorch Lightning provides about [40+ useful trainer flags](https://pytorch-lightning.readthedocs.io/en/latest/common/trainer.html#trainer-flags).
```yaml
# gradient clipping may be enabled to avoid exploding gradients
python run.py +trainer.gradient_clip_val=0.5

# stochastic weight averaging can make your models generalize better
python run.py +trainer.stochastic_weight_avg=true

# run validation loop 4 times during a training epoch
python run.py +trainer.val_check_interval=0.25

# accumulate gradients
python run.py +trainer.accumulate_grad_batches=10
```

</details>


<details>
<summary><b>Easily debug</b></summary>

```yaml
# run 1 train, val and test loop, using only 1 batch
python run.py debug=true

# print full weight summary of all PyTorch modules
python run.py trainer.weights_summary="full"

# print execution time profiling after training ends
python run.py +trainer.profiler="simple"

# raise exception, if any of the parameters or the loss are NaN or +/-inf
python run.py trainer.terminate_on_nan=true

# try overfitting to 1 batch
python run.py +trainer.overfit_batches=1 trainer.max_epochs=20

# use only 20% of the data
python run.py +trainer.limit_train_batches=0.2 \
+trainer.limit_val_batches=0.2 +trainer.limit_test_batches=0.2
```

</details>


<details>
<summary><b>Resume training from checkpoint</b></summary>

> Checkpoint can be either path or URL. Path should be absolute!
```yaml
python run.py +trainer.resume_from_checkpoint="/absolute/path/to/ckpt/name.ckpt"
```
> ⚠️ Currently loading ckpt in Lightning doesn't resume logger experiment, but it will be supported in future Lightning release.

</details>


<details>
<summary><b>Create a sweep over hyperparameters</b></summary>

```yaml
# this will run 6 experiments one after the other,
# each with different combination of batch_size and learning rate
python run.py -m datamodule.batch_size=32,64,128 optimizer.lr=0.001,0.0005
```
> ⚠️ Currently sweeps aren't failure resistant (if one job crashes than the whole sweep crashes), but it will be supported in future Hydra release.

</details>


<details>
<summary><b>Create a sweep over hyperparameters with Optuna</b></summary>

> Using [Optuna Sweeper](https://hydra.cc/docs/next/plugins/optuna_sweeper) plugin doesn't require you to code any boilerplate into your pipeline, everything is defined in a [single config file](configs/config_optuna.yaml)!
```yaml
# this will run hyperparameter search defined in `configs/hparams_search/mnist_optuna.yaml`
# over chosen experiment config
python run.py -m hparams_search=mnist_optuna experiment=exp_example_simple
```

</details>

<details>
<summary><b>Execute all experiments from folder</b></summary>

> Hydra provides special syntax for controlling behavior of multiruns. Learn more [here](https://hydra.cc/docs/next/tutorials/basic/running_your_app/multi-run). The command below executes all experiments from folder [configs/experiment/](configs/experiment/).
```yaml
python run.py -m 'experiment=glob(*)'
```

</details>

<details>
<summary><b>Execute sweep on a remote AWS cluster</b></summary>

> This should be achievable with simple config using [Ray AWS launcher for Hydra](https://hydra.cc/docs/next/plugins/ray_launcher). Example is not yet implemented in this template.

</details>

<details>
<summary><b>Execute sweep on a Linux SLURM cluster</b></summary>

> This should be achievable with simple config using [Submitit launcher for Hydra](https://hydra.cc/docs/plugins/submitit_launcher). Example is not yet implemented in this template.

</details>


<details>
<summary><b>Use Hydra tab completion</b></summary>

> Hydra allows you to autocomplete config argument overrides in shell as you write them, by pressing `tab` key. Learn more [here](https://hydra.cc/docs/tutorials/basic/running_your_app/tab_completion).

</details>
<br>


## :whale:&nbsp; Docker
I recommend the official [nvidia ngc pytorch container](https://ngc.nvidia.com/catalog/containers/nvidia:pytorch/tags) (size: 6GB, it comes with installed Apex for mixed-precision training), or "devel" version of [pytorch/pytorch](https://hub.docker.com/r/pytorch/pytorch).

Custom dockerfiles for the template are provided on branch [`dockerfiles`](https://github.com/ashleve/lightning-hydra-template/tree/dockerfiles). You can use them as a starting point for building your own images.
```yaml
# download image
docker pull nvcr.io/nvidia/pytorch:21.03-py3

# run container from image with GPUs enabled
docker run --gpus all -it --rm nvcr.io/nvidia/pytorch:21.03-py3
```
```yaml
# alternatively build image by yourself using Dockerfile from the mentioned template branch
docker build -t lightning-hydra .
```
<br><br>



## :heart:&nbsp; Contributions
Have a question? Found a bug? Missing a specific feature? Ran into a problem? Feel free to file a new issue or PR with respective title and description. If you already found a solution to your problem, don't hesitate to share it. Suggestions for new best practices and tricks are always welcome!
<br><br><br><br>



## :information_source:&nbsp; Guide

### How To Learn
- First, you should probably get familiar with [PyTorch Lightning](https://www.pytorchlightning.ai)
- Next, go through [Hydra quick start guide](https://hydra.cc/docs/intro/), [basic Hydra tutorial](https://hydra.cc/docs/tutorials/basic/your_first_app/simple_cli/) and [docs about instantiating objects with Hydra](https://hydra.cc/docs/patterns/instantiate_objects/overview)
<br>


### How it works
By design, every run is initialized by [run.py](run.py) file. [train.py](src/train.py) contains training pipeline.
You can create different pipelines for different needs (e.g. for k-fold cross validation or for testing only).

All PyTorch Lightning modules are dynamically instantiated from module paths specified in config, e.g. the model can be instantiated with the following line:
```python
model = hydra.utils.instantiate(config.model)
```
This allows you to easily iterate over new models!<br>
Every time you create a new one, just specify its module path and parameters in appriopriate config file:
```yaml
_target_: src.models.mnist_model.MNISTLitModel
input_size: 784
lin1_size: 256
lin2_size: 256
lin3_size: 256
output_size: 10
lr: 0.001
```
<br>


### Main Project Configuration
Location: [configs/config.yaml](configs/config.yaml)<br>
Main project config contains default training configuration.<br>
It determines how config is composed when simply executing command `python run.py`.<br>
It also specifies everything that shouldn't be managed by experiment configurations.
<details>
<summary><b>Show main project configuration</b></summary>

```yaml
# specify here default training configuration
defaults:
    - trainer: default_trainer.yaml
    - model: mnist_model.yaml
    - datamodule: mnist_datamodule.yaml
    - callbacks: default_callbacks.yaml  # set this to null if you don't want to use callbacks
    - logger: null  # set logger here or use command line (e.g. `python run.py logger=wandb`)


# path to original working directory
# hydra hijacks working directory by changing it to the current log directory
# so it's useful to have this path as a special variable
# learn more here: https://hydra.cc/docs/next/tutorials/basic/running_your_app/working_directory
work_dir: ${hydra:runtime.cwd}


# path to folder with data
data_dir: ${work_dir}/data/


# use `python run.py debug=true` for easy debugging!
# (equivalent to running `python run.py trainer.fast_dev_run=true`)
debug: False


# pretty print config at the start of the run using Rich library
print_config: True


# disable python warnings if they annoy you
disable_warnings: False


# output paths for hydra logs
hydra:
    run:
        dir: logs/runs/${now:%Y-%m-%d}/${now:%H-%M-%S}
    sweep:
        dir: logs/multiruns/${now:%Y-%m-%d_%H-%M-%S}
        subdir: ${hydra.job.num}
```

</details>
<br>


### Experiment Configuration
Location: [configs/experiment](configs/experiment)<br>
You should store all your experiment configurations in this folder.<br>
Experiment configurations allow you to overwrite parameters from main project configuration.

**Simple example**
```yaml
# to execute this experiment run:
# python run.py +experiment=exp_example_simple

defaults:
    - override /trainer: default_trainer.yaml
    - override /model: mnist_model.yaml
    - override /datamodule: mnist_datamodule.yaml
    - override /callbacks: default_callbacks.yaml
    - override /logger: null

# all parameters below will be merged with parameters from default configurations set above
# this allows you to overwrite only specified parameters

seed: 12345

trainer:
    max_epochs: 10
    gradient_clip_val: 0.5

model:
    lin1_size: 128
    lin2_size: 256
    lin3_size: 64
    lr: 0.005

datamodule:
    train_val_test_split: [55_000, 5_000, 10_000]
    batch_size: 64
```
</details>


<details>
<summary><b>Advanced example</b></summary>

```yaml
# to execute this experiment run:
# python run.py +experiment=exp_example_full

defaults:
    - override /trainer: null
    - override /model: null
    - override /datamodule: null
    - override /callbacks: null
    - override /logger: null

# we override default configurations with nulls to prevent them from loading at all
# instead we define all modules and their paths directly in this config,
# so everything is stored in one place for more readability

seed: 12345

trainer:
    _target_: pytorch_lightning.Trainer
    gpus: 0
    min_epochs: 1
    max_epochs: 10
    gradient_clip_val: 0.5

model:
    _target_: src.models.mnist_model.MNISTLitModel
    lr: 0.001
    weight_decay: 0.00005
    input_size: 784
    lin1_size: 256
    lin2_size: 256
    lin3_size: 128
    output_size: 10

datamodule:
    _target_: src.datamodules.mnist_datamodule.MNISTDataModule
    data_dir: ${data_dir}
    train_val_test_split: [55_000, 5_000, 10_000]
    batch_size: 64
    num_workers: 0
    pin_memory: False

logger:
    wandb:
        _target_: pytorch_lightning.loggers.wandb.WandbLogger
        project: "lightning-hydra-template"
        tags: ["best_model", "uwu"]
        notes: "Description of this model."
```

</details>

<br>

### Workflow
1. Write your PyTorch Lightning model (see [mnist_model.py](src/models/mnist_model.py) for example)
2. Write your PyTorch Lightning datamodule (see [mnist_datamodule.py](src/datamodules/mnist_datamodule.py) for example)
3. Write your experiment config, containing paths to your model and datamodule
4. Run training with chosen experiment config: `python run.py +experiment=experiment_name`
<br>

### Logs
Hydra creates new working directory for every executed run. <br>
By default, logs have the following structure:
```
│
├── logs
│   ├── runs                    # Folder for logs generated from single runs
│   │   ├── 2021-02-15              # Date of executing run
│   │   │   ├── 16-50-49                # Hour of executing run
│   │   │   │   ├── .hydra                  # Hydra logs
│   │   │   │   ├── wandb                   # Weights&Biases logs
│   │   │   │   ├── checkpoints             # Training checkpoints
│   │   │   │   └── ...                     # Any other thing saved during training
│   │   │   ├── ...
│   │   │   └── ...
│   │   ├── ...
│   │   └── ...
│   │
│   └── multiruns               # Folder for logs generated from multiruns (sweeps)
│       ├── 2021-02-15_16-50-49     # Date and hour of executing sweep
│       │   ├── 0                       # Job number
│       │   │   ├── .hydra                  # Hydra logs
│       │   │   ├── wandb                   # Weights&Biases logs
│       │   │   ├── checkpoints             # Training checkpoints
│       │   │   └── ...                     # Any other thing saved during training
│       │   ├── 1
│       │   ├── 2
│       │   └── ...
│       ├── ...
│       └── ...
│
```

You can change this structure by modifying paths in [main project configuration](configs/config.yaml).
<br><br>


### Experiment Tracking
PyTorch Lightning supports the most popular logging frameworks:<br>
**[Weights&Biases](https://www.wandb.com/) · [Neptune](https://neptune.ai/) · [Comet](https://www.comet.ml/) · [MLFlow](https://mlflow.org) · [Aim](https://github.com/aimhubio/aim) · [Tensorboard](https://www.tensorflow.org/tensorboard/)**

These tools help you keep track of hyperparameters and output metrics and allow you to compare and visualize results. To use one of them simply complete its configuration in [configs/logger](configs/logger) and run:
 ```yaml
 python run.py logger=logger_name
 ```
You can use many of them at once (see [configs/logger/many_loggers.yaml](configs/logger/many_loggers.yaml) for example).<br>
You can also write your own logger.<br>
Lightning provides convenient method for logging custom metrics from inside LightningModule. Read the docs [here](https://pytorch-lightning.readthedocs.io/en/latest/extensions/logging.html#automatic-logging) or take a look at [MNIST example](src/models/mnist_model.py).
<br><br>



### Inference
Template contains simple example of loading model from checkpoint and running predictions.<br>
Take a look at [inference_example.py](src/utils/inference_example.py).
<br><br>


### Callbacks
Template contains example callbacks enabling better Weights&Biases integration, which you can use as a reference for writing your own callbacks (see [wandb_callbacks.py](src/callbacks/wandb_callbacks.py)).<br>
To support reproducibility: **WatchModelWithWandb**, **UploadCodeToWandbAsArtifact**, **UploadCheckpointsToWandbAsArtifact**.<br>
To provide examples of logging custom visualisations with callbacks only: **LogConfusionMatrixToWandb**, **LogF1PrecRecHeatmapToWandb**.<br>
<br>


### Multi-GPU Training
Lightning supports multiple ways of doing distributed training.<br>
The most common one is DDP, which spawns separate process for each GPU and averages gradients between them. To learn about other approaches read [lightning docs](https://pytorch-lightning.readthedocs.io/en/latest/advanced/multi_gpu.html).

You can run DDP on mnist example with 4 GPUs like this:
```yaml
python run.py trainer.gpus=4 +trainer.accelerator="ddp"
```
⚠️ When using DDP you have to be careful how you write your models - learn more [here](https://pytorch-lightning.readthedocs.io/en/latest/advanced/multi_gpu.html).
<!--
<details>
<summary><b>Use metrics api objects</b></summary>

Use metrics api objects, e.g. `pytorch_lightning.metrics.classification.Accuracy` when logging metrics in `LightningModule`, to ensure proper reduction over multiple GPUs. You can also use `sync_dist` parameter instead with `self.log(..., sync_dist=True)`. Learn more [here](https://pytorch-lightning.readthedocs.io/en/latest/advanced/multi_gpu.html#synchronize-validation-and-test-logging).

</details>

3. Remember `outputs` parameters in hooks like `validation_epoch_end()` will contain only outputs from subset of data processed on given GPU.
4. Init tensors using `type_as` and `register_buffer`. Learn more [here](https://pytorch-lightning.readthedocs.io/en/latest/advanced/multi_gpu.html#init-tensors-using-type-as-and-register-buffer).
5. Make sure your model is pickable. Learn more [here](https://pytorch-lightning.readthedocs.io/en/latest/advanced/multi_gpu.html#make-models-pickleable).
 -->
<br>


### Extra Features
List of extra utilities available in the template:
- loading environment variables from [.env](.env.template) file
- automatic virtual environment setup with [.autoenv](.autoenv.template) file
- pretty printing config with [Rich](https://github.com/willmcgugan/rich) library
- disabling python warnings
- easier access to debug mode
- forcing debug friendly configuration
- forcing multi-gpu friendly configuration
- method for logging hyperparameters to loggers
- (TODO) resuming latest run

You can easily remove any of those by modifying [run.py](run.py) and [src/train.py](src/train.py).
<br><br>


### Limitations
(TODO)
<br><br><br>



## Best Practices
<details>
<summary><b>Use Docker</b></summary>

Docker makes it easy to initialize the whole training environment, e.g. when you want to execute experiments in cloud or on some private computing cluster. You can extend [dockerfiles](https://github.com/ashleve/lightning-hydra-template/tree/dockerfiles) provided in the template with your own instructions for building the image.<br>

</details>

<details>
<summary><b>Use Miniconda</b></summary>

Use miniconda for your python environments (it's usually unnecessary to install full anaconda environment, miniconda should be enough).
It makes it easier to install some dependencies, like cudatoolkit for GPU support.<br>
Example installation:
```yaml
wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh
bash Miniconda3-latest-Linux-x86_64.sh
```
Docker image provided in the template already comes with initialized miniconda environment.

</details>

<details>
<summary><b>Use automatic code formatting</b></summary>

Use pre-commit hooks to standardize code formatting of your project and save mental energy.<br>
Simply install pre-commit package with:
```yaml
pip install pre-commit
```
Next, install hooks from [.pre-commit-config.yaml](.pre-commit-config.yaml):
```yaml
pre-commit install
```
After that your code will be automatically reformatted on every new commit.<br>
Currently template contains configurations of **Black** (python code formatting) and **Isort** (python import sorting). You can exclude chosen files from automatic formatting, by modifying [.pre-commit-config.yaml](.pre-commit-config.yaml).<br>

To reformat all files in the project use command:
```yaml
pre-commit run -a
```

</details>

<details>
<summary><b>Set private environment variables in .env file</b></summary>

System specific variables (e.g. absolute paths to datasets) should not be under version control or it will result in conflict between different users. Your private keys also shouldn't be versioned since you don't want them to be leaked.<br>

Template contains `.env.template` file, which serves as an example. Create a new file called `.env` (this name is excluded from version control in .gitignore).
You should use it for storing environment variables like this:
```yaml
MY_VAR=/home/user/my_system_path
```
All variables from `.env` are loaded in `run.py` automatically.

Hydra allows you to reference any env variable in `.yaml` configs like this:
```yaml
path_to_data: ${env:MY_VAR}
```

</details>

<details>
<summary><b>Name metrics using '/' character</b></summary>

Depending on which logger you're using, it's often useful to define metric name with `/` character:
```python
self.log("train/loss", loss)
```
This way loggers will treat your metrics as belonging to different sections, which helps to get them organised in UI.

</details>

<details>
<summary><b>Follow PyTorch Lightning style guide</b></summary>

The style guide is available [here](https://pytorch-lightning.readthedocs.io/en/latest/starter/style_guide.html).<br>

1. Be explicit in your init. Try to define all the relevant defaults so that the user doesn’t have to guess. Provide type hints. This way your module is reusable across projects!
    ```python
    class LitModel(LightningModule):
        def __init__(self, layer_size: int = 256, lr: float = 0.001):
    ```

2. Preserve the recommended method order.
    ```python
    class LitModel(LightningModule):

        def __init__(...):

        def forward(...):

        def training_step(...)

        def training_step_end(...)

        def training_epoch_end(...)

        def validation_step(...)

        def validation_step_end(...)

        def validation_epoch_end(...)

        def test_step(...)

        def test_step_end(...)

        def test_epoch_end(...)

        def configure_optimizers(...)

        def any_extra_hook(...)
    ```

</details>

<details>
<summary><b>Version control your data and models with DVC</b></summary>

Use [DVC](https://dvc.org) to version control big files, like your data or trained ML models.<br>
To initialize the dvc repository:
```yaml
dvc init
```
To start tracking a file or directory, use `dvc add`:
```yaml
dvc add data/MNIST
```
DVC stores information about the added file (or a directory) in a special .dvc file named data/MNIST.dvc, a small text file with a human-readable format. This file can be easily versioned like source code with Git, as a placeholder for the original data:
```yaml
git add data/MNIST.dvc data/.gitignore
git commit -m "Add raw data"
```

</details>

<details>
<summary><b>Support installing project as a package</b></summary>

It allows other people to easily use your modules in their own projects.
Change name of the `src` folder to your project name and add `setup.py` file:
```python
from setuptools import find_packages, setup

setup(
    name="src",  # you should change "src" to your project name
    version="0.0.0",
    description="Describe Your Cool Project",
    author="",
    author_email="",
    # replace with your own github project link
    url="https://github.com/ashleve/lightning-hydra-template",
    install_requires=["pytorch-lightning>=1.2.0", "hydra-core>=1.0.6"],
    packages=find_packages(),
)
```
Now your project can be installed from local files:
```yaml
pip install -e .
```
Or directly from git repository:
```yaml
pip install git+git://github.com/YourGithubName/your-repo-name.git --upgrade
```
So any file can be easily imported into any other file like so:
```python
from project_name.models.mnist_model import MNISTLitModel
from project_name.datamodules.mnist_datamodule import MNISTDataModule
```

</details>


<details>
<summary><b>Write tests</b></summary>

(TODO)

</details>


<!--
<details>
<summary><b>Use Miniconda</b></summary>

I find myself often running into bugs that come out only in edge cases or on some specific hardware/environment. To speed up the development, I usually constantly execute simple bash scripts that run a couple of quick 1 epoch experiments, like overfitting to 10 batches, training on 25% of data, etc. You can easily modify the commands in the script for your use case. If even 1 epoch is too much for your model, then you can make it run for a couple of batches instead (by using the right trainer flags).<br>

Keep in mind those aren't real tests - it's simply executing commands one after the other, after which you need to take a look in terminal if some of them crashed. It's always best if you write real unit tests for your code.<br>
To execute:
```yaml
bash tests/smoke_tests.sh
```

</details>
 -->
<br>


## Tricks
<details>
<summary><b>Automatic activation of virtual environment and tab completion</b></summary>

Template contains `.autoenv.template` file, which serves as an example. Create a new file called `.autoenv` (this name is excluded from version control in .gitignore).
You can use it to automatically execute shell commands when entering folder:
```bash
# activate conda environment
conda activate myenv

# initialize hydra tab completion for bash
eval "$(python run.py -sc install=bash)"
```

To setup this automation for bash, execute the following line:
```bash
echo "autoenv() { [[ -f \"\$PWD/.autoenv\" ]] && source .autoenv ; } ; cd() { builtin cd \"\$@\" ; autoenv ; } ; autoenv" >> ~/.bashrc
```
**Explanation**<br>
This line appends your `.bashrc` file with 3 commands:
1. `autoenv() { [[ -f \"\$PWD/.autoenv\" ]] && source .autoenv ; }` - this declares the `autoenv()` function, which executes `.autoenv` file if it exists in current work dir
2. `cd() { builtin cd \"\$@\" ; autoenv ; }` - this extends behaviour of `cd` command, to make it execute `autoenv()` function each time you change folder in terminal
3. `autoenv` this is just to ensure the function will also be called when directly openning terminal in any folder


</details>


</details>


<details>
<summary><b>Accessing datamodule attributes in model</b></summary>

The simplest way is to pass datamodule attribute directly to model on initialization:
```python
datamodule = hydra.utils.instantiate(config.datamodule)

model = hydra.utils.instantiate(config.model, some_param=datamodule.some_param)
```
This is not a robust solution, since it assumes all your datamodules have `some_param` attribute available (otherwise the run will crash).
A better solution is to add Omegaconf resolver to your datamodule:
```python
from omegaconf import OmegaConf

# you can place this snippet in your datamodule __init__()
resolver_name = "datamodule"
OmegaConf.register_new_resolver(
    resolver_name,
    lambda name: getattr(self, name),
    use_cache=False
)
```
This way you can reference any datamodule attribute from your config like this:
```yaml
# this will get 'datamodule.some_param' field
some_parameter: ${datamodule: some_param}
```
When later accessing this field, say in your lightning model, it will get automatically resolved based on all resolvers that are registered. Remember not to access this field before datamodule is initialized. **You also need to set resolve to false in print_config() in [run.py](run.py) method or it will throw errors!**
```python
template_utils.print_config(config, resolve=False)
```

</details>

<!--
PrettyErrors and Rich exception handling,
 -->
<br>


## Other Repositories

<details>
<summary><b>Inspirations</b></summary>

This template was inspired by:
[PyTorchLightning/deep-learninig-project-template](https://github.com/PyTorchLightning/deep-learning-project-template),
[drivendata/cookiecutter-data-science](https://github.com/drivendata/cookiecutter-data-science),
[tchaton/lightning-hydra-seed](https://github.com/tchaton/lightning-hydra-seed),
[Erlemar/pytorch_tempest](https://github.com/Erlemar/pytorch_tempest),
[lucmos/nn-template](https://github.com/lucmos/nn-template).

</details>

<details>
<summary><b>Useful repositories</b></summary>

- [pytorch/hydra-torch](https://github.com/pytorch/hydra-torch) - resources for configuring PyTorch classes with Hydra,
- [romesco/hydra-lightning](https://github.com/romesco/hydra-lightning) - resources for configuring PyTorch Lightning classes with Hydra
- [lucmos/nn-template](https://github.com/lucmos/nn-template) - similar template that's easier to start with but less scalable

</details>

<details>
<summary><b>List of repositories using this template</b></summary>

- [ashleve/graph_classification](https://github.com/ashleve/graph_classification) - benchmarking graph neural network architectures on graph classification datasets (Open Graph Benchmarks and image classification from superpixels)

> if you'd like to share your project and add it to the list, feel free to make a PR!

</details>



<br>
<br>
<br>
<br>



**DELETE EVERYTHING ABOVE FOR YOUR PROJECT**

---

<div align="center">

# Your Project Name

<a href="https://pytorch.org/get-started/locally/"><img alt="PyTorch" src="https://img.shields.io/badge/PyTorch-ee4c2c?logo=pytorch&logoColor=white"></a>
<a href="https://pytorchlightning.ai/"><img alt="Lightning" src="https://img.shields.io/badge/-Lightning-792ee5"></a>
<a href="https://hydra.cc/"><img alt="Config: Hydra" src="https://img.shields.io/badge/Config-Hydra-89b8cd"></a>
<a href="https://github.com/ashleve/lightning-hydra-template"><img alt="Template" src="https://img.shields.io/badge/-Lightning--Hydra--Template-017F2F?style=flat&logo=github&labelColor=gray"></a><br>
[![Paper](http://img.shields.io/badge/paper-arxiv.1001.2234-B31B1B.svg)](https://www.nature.com/articles/nature14539)
[![Conference](http://img.shields.io/badge/AnyConference-year-4b44ce.svg)](https://papers.nips.cc/paper/2020)

</div>

## Description
What it does

## How to run
Install dependencies
```yaml
# clone project
git clone https://github.com/YourGithubName/your-repo-name
cd your-repo-name

# [OPTIONAL] create conda environment
conda env create -f conda_env_gpu.yaml -n myenv
conda activate myenv

# install requirements
pip install -r requirements.txt
```

Train model with default configuration
```yaml
# default
python run.py

# train on CPU
python run.py trainer.gpus=0

# train on GPU
python run.py trainer.gpus=1
```

Train model with chosen experiment configuration from [configs/experiment/](configs/experiment/)
```yaml
python run.py +experiment=experiment_name
```

You can override any parameter from command line like this
```yaml
python run.py trainer.max_epochs=20 datamodule.batch_size=64
```

<br>