Merge remote-tracking branch 'gitlab/master'

Author: EikanWang

README.md

@@ -3,10 +3,12 @@
 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](#installation)
-	 - [Install PyTorch from Source](#install-pytorch-from-source)
-	 - [Install Intel Extension for PyTorch from Source](#install-intel-extension-for-pytorch-from-source)
+     - [Install PyTorch from Source](#install-pytorch-from-source)
+     - [Install Intel Extension for PyTorch from Source](#install-intel-extension-for-pytorch-from-source)
  - [Getting Started](#getting-started)
      - [Automatically Mix Precison](#automatically-mix-precision)
+        - [BFloat16](#BFloat16)
+        - [INT8](#int8-quantization)
  - [Contribution](#contribution)
  - [License](#license)
 
@@ -27,7 +29,7 @@ Intel Extension for PyTorch is a Python package to extend official PyTorch. It i
     git submodule update --init --recursive
     ```
 
- 2. Get Intel PyTorch Extension source
+ 2. Get the source code of Intel Extension for PyTorch
     ```bash
     git clone --recursive https://github.com/intel/intel-extension-for-pytorch
     cd intel-extension-for-pytorch
@@ -109,6 +111,8 @@ res = model(input)
 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
 ```python
 import torch
 import torch.nn as nn
@@ -130,6 +134,110 @@ 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:
+```python
+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```):
+```python
+# 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.
+
+```json
+[
+    {
+        "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```):
+```python
+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