Intel® Extension for PyTorch

Intel Extension for PyTorch is a Python package to extend official PyTorch. It is designed to make the Out-of-Box user experience of PyTorch CPU better while achieving good performance. The extension also will be the PR(Pull-Request) buffer for the Intel PyTorch framework dev team. The PR buffer will not only contain functions, but also optimization (for example, take advantage of Intel's new hardware features).

• Installation
  • Install PyTorch from Source
  • Install Intel Extension for PyTorch from Source
• Getting Started
  • Automatically Mix Precison
    • BFloat16
    • INT8
• Contribution
• License

Installation

Install PyTorch from Source

Take Intel-Extension-for-Pytorch v1.2.0 as the example.

1. Get PyTorch v1.7.0 source(Refer to PyTorch guide for more details)

   git clone --recursive https://github.com/pytorch/pytorch
   cd pytorch
   
   # checkout source code to the specified version
   git checkout v1.7.0
   
   # update submodules for the specified PyTorch version
   git submodule sync
   git submodule update --init --recursive
   

2. Get the source code of Intel Extension for PyTorch

   git clone --recursive https://github.com/intel/intel-extension-for-pytorch
   cd intel-extension-for-pytorch
   
   # if you are updating an existing checkout
   git submodule sync
   git submodule update --init --recursive
   

3. Add an new backend for Intel Extension for PyTorch

   # Apply git patch to pytorch code
   cd ${pytorch_directory}
   git apply ${intel_extension_for_pytorch_directory}/torch_patches/xpu-1.7.patch
   

4. Build and install PyTorch (Refer to PyTorch guide for more details)

   cd ${pytorch_directory}
   python setup.py install
   

Install Intel Extension for PyTorch from Source

Install dependencies

pip install lark-parser hypothesis

Install the extension

cd ${intel_extension_for_pytorch_directory}
python setup.py install

Getting Started

If you want to explore Intel Extension for PyTorch, you just need to convert the model and input tensors to the extension device, then the extension will be enabled automatically. Take an example, the code as follows is a model without the extension.

import torch
import torch.nn as nn

class Model(nn.Module):
    def __init__(self):
        super(Model, self).__init__()
        self.linear = nn.Linear(4, 5)

    def forward(self, input):
        return self.linear(input)

input = torch.randn(2, 4)
model = Model()
res = model(input)

You just need to transform the above python script as follows and then the extension will be enabled and accelerate the computation automatically.

import torch
import torch.nn as nn

# Import Extension
import intel_pytorch_extension as ipex

class Model(nn.Module):
    def __init__(self):
        super(Model, self).__init__()
        self.linear = nn.Linear(4, 5)

    def forward(self, input):
        return self.linear(input)

# Convert the input tensor to the Extension device
input = torch.randn(2, 4).to(ipex.DEVICE)
# Convert the model to the Extension device
model = Model().to(ipex.DEVICE)

res = model(input)

Automatically Mix Precision

In addition, Intel Extension for PyTorch supports the mixed precision. It means that some operators of a model may run with Float32 and some other operators may run with BFloat16 or INT8. In traditional, if you want to run a model with a low precision type, you need to convert the parameters and the input tensors to the low precision type manually. And if the model contains some operators that do not support the low precision type, then you have to convert back to Float32. Round after round until the model can run normally. The extension can simply the case, you just need to enable the auto-mix-precision as follows, then you can benefit from the low precision. Currently, the extension only supports BFloat16.

BFloat16

import torch
import torch.nn as nn

import intel_pytorch_extension as ipex
# Automatically mix precision
ipex.enable_auto_mixed_precision(mixed_dtype = torch.bfloat16)

class Model(nn.Module):
    def __init__(self):
        super(Model, self).__init__()
        self.linear = nn.Linear(4, 5)

    def forward(self, input):
        return self.linear(input)

input = torch.randn(2, 4).to(ipex.DEVICE)
model = Model().to(ipex.DEVICE)

res = model(input)

INT8 Quantization

Currently, Intel Extension for PyTorch has supported static and symmetric quantization. Development of dynamic quantization is undergoing. And asymmetric quantization will be enabled once oneDNN is upgraded to v2.0 or higher versions.

How to quantize the following model:

import torch
import torch.nn as nn

class Model(nn.Module):
    def __init__(self):
        super(Model, self).__init__()
        self.conv = nn.Conv2d(3, 64, 7, stride=2)

    def forward(self, input):
        return self.conv(input).relu()

Firstly we need to do calibration step against a representative dataset (set running_mode to calibration):

# Convert the model to the Extension device
model = Model().to(ipex.DEVICE)

# Create a configuration file to save quantization parameters.
conf = ipex.AmpConf(torch.int8)
with torch.no_grad():
    for x in cali_dataset:
        # Run the model under calibration mode to collect quantization parameters
        with ipex.AutoMixPrecision(conf, running_mode='calibration'):
            y = model(x.to(ipex.DEVICE))
# Save the configuration file
conf.save('configure.json')

The content of the configuration file is as follows.

[
    {
        "id": 0,
        "name": "Convolution",
        "algorithm": "min_max",
        "weight_granularity": "per_channel",
        "inputs_scale": [
            25.05583953857422
        ],
        "outputs_scale": [
            43.98969650268555
        ],
        "inputs_uint8_used": [
            false
        ],
        "outputs_uint8_used": [
            false
        ],
        "quantized": true
    },
    {
        "id": 1,
        "name": "Relu",
        "algorithm": "min_max",
        "weight_granularity": "per_channel",
        "inputs_scale": [
            43.98969650268555
        ],
        "outputs_scale": [
            43.98969650268555
        ],
        "inputs_uint8_used": [
            false
        ],
        "outputs_uint8_used": [
            false
        ],
        "quantized": true
    }
]

• id is a sequence number of operators which were quantized statically in the calibration step. Manually changing this value will cause unexpected behaviors.
• name is the name of the operator to be quantized.
• algorithm indicates how to calculate the scales of the observed tensors. Currently only min_max is supported.
• weight_granularity controls how to quantize the operator weights. The Convolution and Linear both supports per_channel and per_tensor. And the other operators only supports per_tensor.
• inputs_scale and outputs_scale are the scales to quantize the input tensors and output tensors respectively.
• inputs_uint8_used and outputs_uint8_used indicate whether to use int8 or uint8. Default value is false, indicating that int8 is used.
• quantized determines whether this operator should be quantized or not during inference.

After doing calibration step, we can use the saved configuration json file to do evalution (set running_mode to inference):

conf = ipex.AmpConf(torch.int8, 'configure.json')
with torch.no_grad():
    for x in cali_dataset:
        with ipex.AutoMixPrecision(conf, running_mode='inference'):
            y = model(x.to(ipex.DEVICE))

Supported Quantization Operators:

• Convoluton
• BatchNorm
• MaxPooling
• AvgPooling
• AdaptivePooling
• Linear
• convolution + relu
• convolution + sum
• convolution + sum + relu
• convolution + BatchNorm

Contribution

Please submit PR or issue to communicate with us or contribute code.

License

Apache License, Version 2.0. As found in LICENSE file.