nncf_pytorch: This repository contains a PyTorch*-based framework and samples for neural networks compression.

# Neural Network Compression Framework (NNCF)

NNCF provides a suite of advanced algorithms for Neural Networks inference optimization in [OpenVINO&trade;](https://github.com/openvinotoolkit/openvino) with minimal accuracy drop.

NNCF is designed to work with models from [PyTorch](https://pytorch.org/) and [TensorFlow](https://www.tensorflow.org/).

NNCF provides samples that demonstrate the usage of compression algorithms for three different use cases on public PyTorch and 
TensorFlow models and datasets: Image Classification, Object Detection and Semantic Segmentation. 
[Compression results](#nncf-compressed-model-zoo) achievable with the NNCF-powered samples can be found in a table at 
the end of this document.

The framework is organized as a Python\* package that can be built and used in a standalone mode. The framework 
architecture is unified to make it easy to add different compression algorithms for both PyTorch and TensorFlow deep 
learning frameworks.

## Key Features

- Automatic, configurable model graph transformation to obtain the compressed model.
  > **NOTE**: Limited support for TensorFlow models. The models created using Sequential or Keras Functional API are only supported.
- Common interface for compression methods.
- GPU-accelerated layers for faster compressed model fine-tuning.
- Distributed training support.
- Configuration file examples for each supported compression algorithm.
- Git patches for prominent third-party repositories ([huggingface-transformers](https://github.com/huggingface/transformers)) demonstrating the process of integrating NNCF into custom training pipelines
- Exporting PyTorch compressed models to ONNX\* checkpoints and TensorFlow compressed models to SavedModel or Frozen Graph format, ready to use with [OpenVINO&trade; toolkit](https://github.com/openvinotoolkit/).
- Support for [Accuracy-Aware model training](./docs/Usage.md#accuracy-aware-model-training) pipelines via the [Adaptive Compression Level Training](./docs/accuracy_aware_model_training/AdaptiveCompressionLevelTraining.md) and [Early Exit Training](./docs/accuracy_aware_model_training/EarlyExitTrainig.md).

## Usage
The NNCF is organized as a regular Python package that can be imported in your target training pipeline script.
The basic workflow is loading a JSON configuration script containing NNCF-specific parameters determining the compression to be applied to your model, and then passing your model along with the configuration script to the `create_compressed_model` function.
This function returns a model with additional modifications necessary to enable algorithm-specific compression during fine-tuning and handle to the object allowing you to control the compression during the training process:

### Usage example with PyTorch

```python
import torch
import nncf  # Important - should be imported directly after torch

from nncf import NNCFConfig
from nncf.torch import create_compressed_model, register_default_init_args

# Instantiate your uncompressed model
from torchvision.models.resnet import resnet50
model = resnet50()

# Load a configuration file to specify compression
nncf_config = NNCFConfig.from_json("resnet50_int8.json")

# Provide data loaders for compression algorithm initialization, if necessary
import torchvision.datasets as datasets
representative_dataset = datasets.ImageFolder("/path")
init_loader = torch.utils.data.DataLoader(representative_dataset)
nncf_config = register_default_init_args(nncf_config, init_loader)

# Apply the specified compression algorithms to the model
compression_ctrl, compressed_model = create_compressed_model(model, nncf_config)

# Now use compressed_model as a usual torch.nn.Module 
# to fine-tune compression parameters along with the model weights

# ... the rest of the usual PyTorch-powered training pipeline

# Export to ONNX or .pth when done fine-tuning
compression_ctrl.export_model("compressed_model.onnx")
torch.save(compressed_model.state_dict(), "compressed_model.pth")
```

### Usage example with TensorFlow
```python
import tensorflow as tf

from nncf import NNCFConfig
from nncf.tensorflow import create_compressed_model, register_default_init_args

# Instantiate your uncompressed model
from tensorflow.keras.applications import ResNet50
model = ResNet50()

# Load a configuration file to specify compression
nncf_config = NNCFConfig.from_json("resnet50_int8.json")

# Provide dataset for compression algorithm initialization
representative_dataset = tf.data.Dataset.list_files("/path/*.jpeg")
nncf_config = register_default_init_args(nncf_config, representative_dataset, batch_size=1)

# Apply the specified compression algorithms to the model
compression_ctrl, compressed_model = create_compressed_model(model, nncf_config)

# Now use compressed_model as a usual Keras model
# to fine-tune compression parameters along with the model weights

# ... the rest of the usual TensorFlow-powered training pipeline

# Export to Frozen Graph, TensorFlow SavedModel or .h5  when done fine-tuning 
compression_ctrl.export_model("compressed_model.pb", save_format='frozen_graph')
```

For a more detailed description of NNCF usage in your training code, see [this tutorial](docs/Usage.md). 
For in-depth examples of NNCF integration, browse the [sample scripts](#model-compression-samples) code, or the [example patches](#third-party-repository-integration) to third-party repositories.

## Model Compression Samples

For a quicker start with NNCF-powered compression, you can also try the sample scripts, each of which provides a basic training pipeline for classification, semantic segmentation and object detection neural network training correspondingly.

To run the samples please refer to the corresponding tutorials:

- PyTorch samples:
  - [Image Classification sample](examples/torch/classification/README.md)
  - [Object Detection sample](examples/torch/object_detection/README.md)
  - [Semantic Segmentation sample](examples/torch/semantic_segmentation/README.md)
- TensorFlow samples:
  - [Image Classification sample](examples/tensorflow/classification/README.md)
  - [Object Detection sample](examples/tensorflow/object_detection/README.md)
  - [Instance Segmentation sample](examples/tensorflow/segmentation/README.md)

## Model Compression Notebooks

A collection of ready-to-run Jupyter* notebooks are also available to demonstrate how to use NNCF compression algorithms
to optimize models for inference with the OpenVINO Toolkit.
- [Optimizing PyTorch models with NNCF of OpenVINO by 8-bit quantization](https://github.com/openvinotoolkit/openvino_notebooks/tree/main/notebooks/302-pytorch-quantization-aware-training)
- [Optimizing TensorFlow models with NNCF of OpenVINO by 8-bit quantization](https://github.com/openvinotoolkit/openvino_notebooks/tree/main/notebooks/305-tensorflow-quantization-aware-training)
- [Post-Training Quantization of Pytorch model with NNCF](https://github.com/openvinotoolkit/openvino_notebooks/tree/main/notebooks/112-pytorch-post-training-quantization-nncf)

## Third-party repository integration
NNCF may be straightforwardly integrated into training/evaluation pipelines of third-party repositories.

### Used by

- [OpenVINO Training Extensions](https://github.com/openvinotoolkit/training_extensions)
  
  NNCF is integrated into OpenVINO Training Extensions as model optimization backend. So you can train, optimize and export new models based on the available model templates as well as run exported models with OpenVINO.

### Git patches for third-party repository
See [third_party_integration](./third_party_integration) for examples of code modifications (Git patches and base commit IDs are provided) that are necessary to integrate NNCF into the following repositories:
  - [huggingface-transformers](third_party_integration/huggingface_transformers/README.md)

## System requirements
- Ubuntu\* 18.04 or later (64-bit)
- Python\* 3.6.2 or later
- Supported frameworks:
  - PyTorch\* >=1.5.0, <=1.9.1 (1.8.0 not supported)
  - TensorFlow\* >=2.4.0, <=2.5.3

This repository is tested on Python* 3.6.2+, PyTorch* 1.9.1 (NVidia CUDA\* Toolkit 10.2) and TensorFlow* 2.5.3 (NVidia CUDA\* Toolkit 11.2).

## Installation
We suggest to install or use the package in the [Python virtual environment](https://docs.python.org/3/tutorial/venv.html).

If you want to optimize a model from PyTorch, install PyTorch by following [PyTorch installation guide](https://pytorch.org/get-started/locally/#start-locally). 
If you want to optimize a model from TensorFlow, install TensorFlow by following [TensorFlow installation guide](https://www.tensorflow.org/install/).

#### As a package built from a checked-out repository:

Install the package and its dependencies by running the following in the repository root directory:
```
python setup.py install
```
Alternatively, If you don't install any backend you can install NNCF and PyTorch in one line with:
```
python setup.py install --torch
```
Install NNCF and TensorFlow in one line:
```
python setup.py install --tf
```

_NB_: For launching example scripts in this repository, we recommend replacing the `install` option above with `develop` and setting the `PYTHONPATH` variable to the root of the checked-out repository.

#### As a PyPI package:

NNCF can be installed as a regular PyPI package via pip:
```
pip install nncf
```
Alternatively, If you don't install any backend you can install NNCF and PyTorch in one line with:
```
pip install nncf[torch]
```
Install NNCF and TensorFlow in one line:
```
pip install nncf[tf]
```

NNCF is also available via [conda](https://anaconda.org/conda-forge/nncf):
```
conda install -c conda-forge nncf
```

#### From a specific commit hash using pip:
```python
pip install git+https://github.com/openvinotoolkit/nncf@bd189e2#egg=nncf
```
Note that in order for this to work for pip versions >= 21.3, your Git version must be at least 2.22.

#### As a Docker image
Use one of the Dockerfiles in the [docker](./docker) directory to build an image with an environment already set up and ready for running NNCF [sample scripts](#model-compression-samples).

## Contributing
Refer to the [CONTRIBUTING.md](./CONTRIBUTING.md) file for guidelines on contributions to the NNCF repository.

## NNCF Compressed Model Zoo

Results achieved using sample scripts, example patches to third-party repositories and NNCF configuration files provided 
with this repository. See README.md files for [sample scripts](#model-compression-samples) and [example patches](#third-party-repository-integration) 
to find instruction and links to exact configuration files and final checkpoints.
- [PyTorch models](#pytorch-models)
  * [Classification](#pytorch_classification)
  * [Object detection](#pytorch_object_detection)
  * [Semantic segmentation](#pytorch_semantic_segmentation)
  * [Natural language processing (3rd-party training pipelines)](#pytorch_nlp)
- [TensorFlow models](#tensorflow-models)
  * [Classification](#tensorflow_classification)
  * [Object detection](#tensorflow_object_detection)
  * [Instance segmentation](#tensorflow_instance_segmentation)

### PyTorch models

<a name="pytorch_classification"></a>
#### Classification

<a name="pytorch_object_detection"></a>
#### Object detection

<a name="pytorch_semantic_segmentation"></a>
#### Semantic segmentation

<a name="pytorch_nlp"></a>
#### NLP (HuggingFace Transformers-powered models)

|PyTorch Model|<img width="20" height="1">Compression algorithm<img width="20" height="1">|Dataset|Accuracy (Drop) %|
| :---: | :---: | :---: | :---: |
|BERT-base-chinese|INT8|XNLI|77.22 (0.46)|
|BERT-base-cased|INT8|CoNLL2003|99.18 (-0.01)|
|BERT-base-cased|INT8|MRPC|84.8 (-0.24)|
|BERT-large (Whole Word Masking)|INT8|SQuAD v1.1|F1: 92.68 (0.53)|
|RoBERTa-large|INT8|MNLI|matched: 89.25 (1.35)|
|DistilBERT-base|INT8|SST-2|90.3 (0.8)|
|MobileBERT|INT8|SQuAD v1.1|F1: 89.4 (0.58)|
|GPT-2|INT8|WikiText-2 (raw)|perplexity: 20.9 (-1.17)|

### TensorFlow models

<a name="tensorflow_classification"></a>
#### Classification

<a name="tensorflow_object_detection"></a>
#### Object detection

<a name="tensorflow_instance_segmentation"></a>
#### Instance segmentation

## Citing

```
@article{kozlov2020neural,
    title =   {Neural network compression framework for fast model inference},
    author =  {Kozlov, Alexander and Lazarevich, Ivan and Shamporov, Vasily and Lyalyushkin, Nikolay and Gorbachev, Yury},
    journal = {arXiv preprint arXiv:2002.08679},
    year =    {2020}
}
```

## Legal Information
[*] Other names and brands may be claimed as the property of others.

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