**The lightweight PyTorch wrapper for high-performance AI research. Scale your models, not the boilerplate.** ---

Website • Key Features • How To Use • Docs • Examples • Community • Grid AI • Licence

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###### *Codecov is > 90%+ but build delays may show less --- ## PyTorch Lightning is just organized PyTorch Lightning disentangles PyTorch code to decouple the science from the engineering. ![PT to PL](/docs/source/_images/general/pl_quick_start_full_compressed.gif) --- ## Lightning Philosophy Lightning is designed with these principles in mind: Principle 1: Enable maximal flexibility. Principle 2: Abstract away unecessary boilerplate, but make it accessible when needed. Principle 3: Systems should be self-contained (ie: optimizers, computation code, etc). Principle 4: Deep learning code should be organized into 4 distinct categories. - Research code (the LightningModule). - Engineering code (you delete, and is handled by the Trainer). - Non-essential research code (logging, etc... this goes in Callbacks). - Data (use PyTorch Dataloaders or organize them into a LightningDataModule). Once you do this, you can train on multiple-GPUs, TPUs, CPUs and even in 16-bit precision without changing your code! Get started with our [2 step guide](https://pytorch-lightning.readthedocs.io/en/stable/new-project.html) --- ## Inference Lightning is also designed for the fast inference AI researchers and production teams need to scale up things like BERT and self-supervised learning. Lightning can automatically export to ONNX or TorchScript for those cases. --- ## Trending contributors [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/0)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/0) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/1)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/1) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/2)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/2) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/3)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/3) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/4)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/4) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/5)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/5) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/6)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/6) [![](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/images/7)](https://sourcerer.io/fame/williamFalcon/pytorchlightning/pytorch-lightning/links/7) --- ## Continuous Integration
| System / PyTorch ver. | 1.3 (min. req.)* | 1.4 | 1.5 | 1.6 (latest) | 1.7 (nightly) | | :---: | :---: | :---: | :---: | :---: | :---: | | Conda py3.7 [linux] | [![PyTorch & Conda](https://github.com/PyTorchLightning/pytorch-lightning/workflows/PyTorch%20&%20Conda/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22PyTorch+%26+Conda%22+branch%3Amaster) | [![PyTorch & Conda](https://github.com/PyTorchLightning/pytorch-lightning/workflows/PyTorch%20&%20Conda/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22PyTorch+%26+Conda%22+branch%3Amaster) | [![PyTorch & Conda](https://github.com/PyTorchLightning/pytorch-lightning/workflows/PyTorch%20&%20Conda/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22PyTorch+%26+Conda%22+branch%3Amaster) | [![PyTorch & Conda](https://github.com/PyTorchLightning/pytorch-lightning/workflows/PyTorch%20&%20Conda/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22PyTorch+%26+Conda%22+branch%3Amaster) | [![PyTorch & Conda](https://github.com/PyTorchLightning/pytorch-lightning/workflows/PyTorch%20&%20Conda/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22PyTorch+%26+Conda%22+branch%3Amaster) | | Linux py3.7 [GPUs**] | - | - |[![Build Status](http://104.154.220.231/api/badges/PyTorchLightning/pytorch-lightning/status.svg)](http://104.154.220.231/PyTorchLightning/pytorch-lightning) | - | - | | Linux py3.7 [TPUs***] | - | - | - | [![TPU tests](https://github.com/PyTorchLightning/pytorch-lightning/workflows/TPU%20tests/badge.svg)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22TPU+tests%22+branch%3Amaster) | - | | Linux py3.6 / py3.7 / py3.8 | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | - | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | | OSX py3.6 / py3.7 | - | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | | Windows py3.6 / py3.7 / py3.8 | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | - | [![CI complete testing](https://github.com/PyTorchLightning/pytorch-lightning/workflows/CI%20complete%20testing/badge.svg?event=push)](https://github.com/PyTorchLightning/pytorch-lightning/actions?query=workflow%3A%22CI+testing%22) | - | - _\* `torch>=1.4` is the minimal pytorch version for Python 3.8_ - _\** tests run on two NVIDIA K80_ - _\*** tests run on Google GKE TPUv2/3_ - _TPU w/ py3.6/py3.7 means we support Colab and Kaggle env._
--- ## How To Use #### Step 0: Install Simple installation from PyPI ```bash pip install pytorch-lightning ``` From Conda ```bash conda install pytorch-lightning -c conda-forge ``` Install bleeding-edge (no guarantees) ```bash pip install git+https://github.com/PytorchLightning/pytorch-lightning.git@master --upgrade ``` #### Step 0: Add these imports ```python import os import torch from torch import nn import torch.nn.functional as F from torchvision.datasets import MNIST from torch.utils.data import DataLoader, random_split from torchvision import transforms import pytorch_lightning as pl ``` #### Step 1: Define a LightningModule (nn.Module subclass) A LightningModule defines a full *system* (ie: a GAN, autoencoder, BERT or a simple Image Classifier). ```python class LitAutoEncoder(pl.LightningModule): def __init__(self): super().__init__() self.encoder = nn.Sequential(nn.Linear(28 * 28, 128), nn.ReLU(), nn.Linear(128, 3)) self.decoder = nn.Sequential(nn.Linear(3, 128), nn.ReLU(), nn.Linear(128, 28 * 28)) def forward(self, x): # in lightning, forward defines the prediction/inference actions embedding = self.encoder(x) return embedding def training_step(self, batch, batch_idx): # training_step defined the train loop. It is independent of forward x, y = batch x = x.view(x.size(0), -1) z = self.encoder(x) x_hat = self.decoder(z) loss = F.mse_loss(x_hat, x) self.log('train_loss', loss) return loss def configure_optimizers(self): optimizer = torch.optim.Adam(self.parameters(), lr=1e-3) return optimizer ``` ###### Note: Training_step defines the training loop. Forward defines how the LightningModule behaves during inference/prediction. #### Step 2: Train! ```python dataset = MNIST(os.getcwd(), download=True, transform=transforms.ToTensor()) train, val = random_split(dataset, [55000, 5000]) autoencoder = LitAutoEncoder() trainer = pl.Trainer() trainer.fit(autoencoder, DataLoader(train), DataLoader(val)) ``` #### And without changing a single line of code, you could run on GPU/TPUss ```python # 8 GPUs trainer = Trainer(max_epochs=1, gpus=8) # 256 GPUs trainer = Trainer(max_epochs=1, gpus=8, num_nodes=32) # TPUs trainer = Trainer(tpu_cores=8) ``` #### And even export for production via onnx or torchscript ```python # torchscript autoencoder = LitAutoEncoder() torch.jit.save(autoencoder.to_torchscript(), "model.pt") # onnx with tempfile.NamedTemporaryFile(suffix='.onnx', delete=False) as tmpfile: autoencoder = LitAutoEncoder() input_sample = torch.randn((1, 64)) autoencoder.to_onnx(tmpfile.name, input_sample, export_params=True) os.path.isfile(tmpfile.name) ``` #### For advanced users, you can still own complex training loops ```python class LitAutoEncoder(pl.LightningModule): def training_step(self, batch, batch_idx, opt_idx): (opt_a, opt_b) = self.optimizers() loss_a = ... self.manual_backward(loss_a, opt_a) opt_a.step() opt_a.zero_grad() loss_b = ... self.manual_backward(loss_b, opt_b, retain_graph=True) self.manual_backward(loss_b, opt_b) opt_b.step() opt_b.zero_grad() ``` --- ## Key Features * Scale your models to run on any hardware (CPU, GPUs, TPUs) without changing your model * Making code more readable by decoupling the research code from the engineering * Easier to reproduce * Less error prone by automating most of the training loop and tricky engineering * Keeps all the flexibility (LightningModules are still PyTorch modules), but removes a ton of boilerplate * Lightning has out-of-the-box integration with the popular logging/visualizing frameworks ([Tensorboard](https://pytorch.org/docs/stable/tensorboard.html), [MLFlow](https://mlflow.org/), [Neptune.ai](https://neptune.ai/), [Comet.ml](https://www.comet.ml/site/), [Wandb](https://www.wandb.com/)). * [Tested rigorously with every new PR](https://github.com/PyTorchLightning/pytorch-lightning/tree/master/tests). We test every combination of PyTorch and Python supported versions, every OS, multi GPUs and even TPUs. * Minimal running speed overhead (about 300 ms per epoch compared with pure PyTorch). ### Lightning automates 40+ parts of DL/ML research - GPU training - Distributed GPU (cluster) training - TPU training - EarlyStopping - Logging/Visualizing - Checkpointing - Experiment management - [Full list here](https://pytorch-lightning.readthedocs.io/en/latest/#common-use-cases) --- ## Examples ###### Hello world [MNIST hello world](https://colab.research.google.com/github/PytorchLightning/pytorch-lightning/blob/master/notebooks/01-mnist-hello-world.ipynb) [MNIST on TPUs](https://colab.research.google.com/drive/1-_LKx4HwAxl5M6xPJmqAAu444LTDQoa3) ###### Contrastive Learning [BYOL](https://pytorch-lightning-bolts.readthedocs.io/en/latest/self_supervised_models.html#byol) [CPC v2](https://pytorch-lightning-bolts.readthedocs.io/en/latest/self_supervised_models.html#cpc-v2) [Moco v2](https://pytorch-lightning-bolts.readthedocs.io/en/latest/self_supervised_models.html#moco-v2) [SIMCLR](https://pytorch-lightning-bolts.readthedocs.io/en/latest/self_supervised_models.html#simclr) ###### NLP [BERT](https://colab.research.google.com/github/PytorchLightning/pytorch-lightning/blob/master/notebooks/04-transformers-text-classification.ipynb) [GPT-2](https://pytorch-lightning-bolts.readthedocs.io/en/latest/convolutional.html#gpt-2) ###### Reinforcement Learning [DQN](https://colab.research.google.com/drive/1F_RNcHzTfFuQf-LeKvSlud6x7jXYkG31#scrollTo=NWvMLBDySQI5) [Dueling-DQN](https://pytorch-lightning-bolts.readthedocs.io/en/latest/reinforce_learn.html#dueling-dqn) [Reinforce](https://pytorch-lightning-bolts.readthedocs.io/en/latest/reinforce_learn.html#reinforce) ###### Vision [GAN](https://colab.research.google.com/github/PytorchLightning/pytorch-lightning/blob/master/notebooks/03-basic-gan.ipynb) ###### Classic ML [Logistic Regression](https://pytorch-lightning-bolts.readthedocs.io/en/latest/classic_ml.html#logistic-regression) [Linear Regression](https://pytorch-lightning-bolts.readthedocs.io/en/latest/classic_ml.html#linear-regression) --- ## Community The lightning community is maintained by - [16 core contributors](https://pytorch-lightning.readthedocs.io/en/latest/governance.html) who are all a mix of professional engineers, Research Scientists, Ph.D. students from top AI labs. - 280+ community contributors. Lightning is also part of the [PyTorch ecosystem](https://pytorch.org/ecosystem/) which requires projects to have solid testing, documentation and support. ### Asking for help If you have any questions please: 1. [Read the docs](https://pytorch-lightning.rtfd.io/en/latest/). 2. [Look it up in our forum (or add a new question)](https://forums.pytorchlightning.ai/) 2. [Search through the issues](https://github.com/PytorchLightning/pytorch-lightning/issues?utf8=%E2%9C%93&q=my++question). 3. [Join our slack](https://join.slack.com/t/pytorch-lightning/shared_invite/zt-f6bl2l0l-JYMK3tbAgAmGRrlNr00f1A). 4. [Ask on stackoverflow](https://stackoverflow.com/questions/ask?guided=false) with the tag pytorch-lightning. ### Funding Building open-source software with only a few part-time people is hard! [We're venture funded](https://techcrunch.com/2020/10/08/grid-ai-raises-18-6m-series-a-to-help-ai-researchers-and-engineers-bring-their-models-to-production/) and backed by some of the top VC funds in the world, [Index Ventures](https://www.indexventures.com/companies/), [Bain Capital Ventures](https://www.baincapitalventures.com/portfolio/), [First Minute Capital](https://firstminute.capital/companies). Their funding ensures we can continue to build awesome tooling like Grid, give you around the clock support, hire a full-time staff, attend conferences, and move faster through implementing features you request. To supercharge your research and production work, visit our [Grid.ai platform](https://www.grid.ai/) --- ## Grid AI Grid AI is our native platform for training models at scale on the cloud! **Sign up for [early access here](https://www.grid.ai/)** To use grid, take your regular command: ``` python my_model.py --learning_rate 1e-6 --layers 2 --gpus 4 ``` And change it to use the grid train command: ``` grid train --grid_gpus 4 my_model.py --learning_rate 'uniform(1e-6, 1e-1, 20)' --layers '[2, 4, 8, 16]' ``` The above command will launch (20 * 4) experiments each running on 4 GPUs (320 GPUs!) - by making ZERO changes to your code. --- ## Licence Please observe the Apache 2.0 license that is listed in this repository. In addition the Lightning framework is Patent Pending. ## BibTeX If you want to cite the framework feel free to use this (but only if you loved it 😊): ```bibtex @article{falcon2019pytorch, title={PyTorch Lightning}, author={Falcon, WA}, journal={GitHub. Note: https://github.com/PyTorchLightning/pytorch-lightning}, volume={3}, year={2019} } ```