pytorch-ignite 0.5.0.dev20200712

A lightweight library to help with training neural networks in PyTorch.

TL;DR

Ignite is a high-level library to help with training and evaluating neural networks in PyTorch flexibly and transparently.

Click on the image to see complete code

Features

• Less code than pure PyTorch while ensuring maximum control and simplicity

• Library approach and no program's control inversion - Use ignite where and when you need

• Extensible API for metrics, experiment managers, and other components

Table of Contents

• Why Ignite?
• Installation
• Getting Started
• Documentation
• Structure
• Examples
  • Tutorials
  • Reproducible Training Examples
• Communication
• Contributing
• Projects using Ignite
• About the team

Why Ignite?

Ignite is a library that provides three high-level features:

• Extremely simple engine and event system
• Out-of-the-box metrics to easily evaluate models
• Built-in handlers to compose training pipeline, save artifacts and log parameters and metrics

Simplified training and validation loop

No more coding for/while loops on epochs and iterations. Users instantiate engines and run them.

Example

from ignite.engine import Engine, Events, create_supervised_evaluator
from ignite.metrics import Accuracy


# Setup training engine:
def train_step(engine, batch):
    # Users can do whatever they need on a single iteration 
    # E.g. forward/backward pass for any number of models, optimizers etc
    # ...

trainer = Engine(train_step)

# Setup single model evaluation engine
evaluator = create_supervised_evaluator(model, metrics={"accuracy": Accuracy()})

def validation():        
    state = evaluator.run(validation_data_loader)
    # print computed metrics 
    print(trainer.state.epoch, state.metrics)

# Run model's validation at the end of each epoch
trainer.add_event_handler(Events.EPOCH_COMPLETED, validation)

# Start the training
trainer.run(training_data_loader, max_epochs=100)

Power of Events & Handlers

The cool thing with handlers is that they offer unparalleled flexibility (compared to say, callbacks). Handlers can be any function: e.g. lambda, simple function, class method etc. Thus, we do not require to inherit from an interface and override its abstract methods which could unnecessarily bulk up your code and its complexity.

Execute any number of functions whenever you wish

Examples

trainer.add_event_handler(Events.STARTED, lambda _: print("Start training"))

# attach handler with args, kwargs
mydata = [1, 2, 3, 4]
logger = ...

def on_training_ended(data):
    print("Training is ended. mydata={}".format(data))
    # User can use variables from another scope  
    logger.info("Training is ended")


trainer.add_event_handler(Events.COMPLETED, on_training_ended, mydata)
# call any number of functions on a single event
trainer.add_event_handler(Events.COMPLETED, lambda engine: print(engine.state.times))

@trainer.on(Events.ITERATION_COMPLETED)
def log_something(engine):
    print(engine.state.output)

Built-in events filtering

Examples

# run the validation every 5 epochs
@trainer.on(Events.EPOCH_COMPLETED(every=5))
def run_validation():
    # run validation

# change some training variable once on 20th epoch
@trainer.on(Events.EPOCH_STARTED(once=20))
def change_training_variable():
    # ...

# Trigger handler with customly defined frequency
@trainer.on(Events.ITERATION_COMPLETED(event_filter=first_x_iters))
def log_gradients():
    # ...

Stack events to share some actions

Examples

Events can be stacked together to enable multiple calls:

@trainer.on(Events.COMPLETED | Events.EPOCH_COMPLETED(every=10))
def run_validation():
    # ...

Custom events to go beyond standard events

Examples

Custom events related to backward and optimizer step calls:

class BackpropEvents(EventEnum):
    BACKWARD_STARTED = 'backward_started'
    BACKWARD_COMPLETED = 'backward_completed'
    OPTIM_STEP_COMPLETED = 'optim_step_completed'

def update(engine, batch):
    # ...
    loss = criterion(y_pred, y)
    engine.fire_event(BackpropEvents.BACKWARD_STARTED)
    loss.backward()
    engine.fire_event(BackpropEvents.BACKWARD_COMPLETED)
    optimizer.step()
    engine.fire_event(BackpropEvents.OPTIM_STEP_COMPLETED)
    # ...    

trainer = Engine(update)
trainer.register_events(*BackpropEvents)

@trainer.on(BackpropEvents.BACKWARD_STARTED)
def function_before_backprop(engine):
    # ...

• Complete snippet can be found here.
• Another use-case of custom events: trainer for Truncated Backprop Through Time.

Out-of-the-box metrics

• Metrics for various tasks: Precision, Recall, Accuracy, Confusion Matrix, IoU etc, ~20 regression metrics.

• Users can also compose their own metrics with ease from existing ones using arithmetic operations or torch methods.

Example

precision = Precision(average=False)
recall = Recall(average=False)
F1_per_class = (precision * recall * 2 / (precision + recall))
F1_mean = F1_per_class.mean()  # torch mean method
F1_mean.attach(engine, "F1")

Installation

From pip:

pip install pytorch-ignite

From conda:

conda install ignite -c pytorch

From source:

pip install git+https://github.com/pytorch/ignite

Nightly releases

From pip:

pip install --pre pytorch-ignite

From conda (this suggests to install pytorch nightly release instead of stable version as dependency):

conda install ignite -c pytorch-nightly

Getting Started

Few pointers to get you started:

• Quick Start Guide: Essentials of getting a project up and running
• Concepts of the library: Engine, Events & Handlers, State, Metrics
• Full-featured template examples (coming soon ...)

Documentation

• Stable API documentation and an overview of the library: https://pytorch.org/ignite/
• Development version API documentation: https://pytorch.org/ignite/master/
• FAQ and "Questions on Github".
• Project's Roadmap

Additional Materials

• 8 Creators and Core Contributors Talk About Their Model Training Libraries From PyTorch Ecosystem
• Ignite Posters from Pytorch Developer Conferences:
  • 2019
  • 2018

Examples

Complete list of examples can be found here.

Tutorials

• Text Classification using Convolutional Neural Networks
• Variational Auto Encoders
• Convolutional Neural Networks for Classifying Fashion-MNIST Dataset
• Training Cycle-GAN on Horses to Zebras with Nvidia/Apex - logs on W&B
• Another training Cycle-GAN on Horses to Zebras with Native Torch CUDA AMP - logs on W&B
• Finetuning EfficientNet-B0 on CIFAR100
• Hyperparameters tuning with Ax
• Basic example of LR finder on MNIST
• Benchmark mixed precision training on Cifar100: torch.cuda.amp vs nvidia/apex
• MNIST training on a single TPU
• CIFAR10 Training on multiple TPUs

Reproducible Training Examples

Inspired by torchvision/references, we provide several reproducible baselines for vision tasks:

• ImageNet - logs on Ignite Trains server coming soon ...
• Pascal VOC2012 - logs on Ignite Trains server coming soon ...

Features:

• Distributed training with mixed precision by nvidia/apex
• Experiments tracking with MLflow, Polyaxon or TRAINS

Communication

• GitHub issues: questions, bug reports, feature requests, etc.

• Discuss.PyTorch, category "Ignite".

• PyTorch Slack at #pytorch-ignite channel. Request access.

User feedback

We have created a form for "user feedback". We appreciate any type of feedback and this is how we would like to see our community:

• If you like the project and want to say thanks, this the right place.
• If you do not like something, please, share it with us and we can see how to improve it.

Thank you !

Contributing

Please see the contribution guidelines for more information.

As always, PRs are welcome :)

Projects using Ignite

Research papers

• BatchBALD: Efficient and Diverse Batch Acquisition for Deep Bayesian Active Learning
• A Model to Search for Synthesizable Molecules
• Localised Generative Flows
• Extracting T Cell Function and Differentiation Characteristics from the Biomedical Literature
• Variational Information Distillation for Knowledge Transfer
• XPersona: Evaluating Multilingual Personalized Chatbot
• CNN-CASS: CNN for Classification of Coronary Artery Stenosis Score in MPR Images
• Bridging Text and Video: A Universal Multimodal Transformer for Video-Audio Scene-Aware Dialog
• Adversarial Decomposition of Text Representation
• Uncertainty Estimation Using a Single Deep Deterministic Neural Network

Blog articles, tutorials, books

• State-of-the-Art Conversational AI with Transfer Learning
• Tutorial on Transfer Learning in NLP held at NAACL 2019
• Deep-Reinforcement-Learning-Hands-On-Second-Edition, published by Packt
• Once Upon a Repository: How to Write Readable, Maintainable Code with PyTorch
• The Hero Rises: Build Your Own SSD
• Using Optuna to Optimize PyTorch Ignite Hyperparameters

Toolkits

• Project MONAI - AI Toolkit for Healthcare Imaging
• DeepSeismic - Deep Learning for Seismic Imaging and Interpretation
• Nussl - a flexible, object oriented Python audio source separation library

Others

• Implementation of "Attention is All You Need" paper
• Implementation of DropBlock: A regularization method for convolutional networks in PyTorch
• Kaggle Kuzushiji Recognition: 2nd place solution
• Unsupervised Data Augmentation experiments in PyTorch
• Hyperparameters tuning with Optuna
• Logging with ChainerUI

See other projects at "Used by"

If your project implements a paper, represents other use-cases not covered in our official tutorials, Kaggle competition's code or just your code presents interesting results and uses Ignite. We would like to add your project in this list, so please send a PR with brief description of the project.

About the team & Disclaimer

This repository is operated and maintained by volunteers in the PyTorch community in their capacities as individuals (and not as representatives of their employers). See the "About us" page for a list of core contributors. For questions and issues, please see the various channels here.