Intel® Distribution of OpenVINO™ Toolkit Tuning Guide on 3rd Generation Intel® Xeon® Scalable Processors Based Platform

Published: 08/16/2021

Introduction

This guide is for users who are already familiar with Intel® Distribution of OpenVINO™ toolkit. It provides hardware and software configurations that provide the best performance for most situations. However, please carefully consider these settings for their specific scenarios, since Intel® Distribution of OpenVINO™ toolkit can be deployed in multiple ways.

OpenVINO™ toolkit is a comprehensive toolkit based on AI and deep learning inference for quickly developing applications to emulate human vision, automate speech recognition, process natural language, create recommendation systems, and more including:

  • Enabling Convolutional Neural Networks (CNN) on edge devices for deep learning

  • Supporting heterogeneous execution across an Intel® CPU, Intel® Integrated Graphics, Intel® Neural Compute Stick 2 and Intel® Vision Accelerator Design with Intel® Movidius™ VPUs

  • Speeding time-to-market via an easy-to-use library of computer vision functions and pre-optimized kernels. OpenVino also includes optimized calls for computer vision standards, including OpenCV* and OpenCL&trade.

3rd Generation Intel® Xeon® Scalable processors deliver industry-leading, workload-optimized platforms with built-in AI acceleration, providing a seamless performance foundation to help speed the transformative impact of data, from the multi-cloud to the intelligent edge and back.

OpenVINO™ Toolkit Workflow

The following diagram illustrates the typical OpenVINO™ workflow:

Typical workflow

Figure 1. Typical OpenVINO™ workflow [1]

OpenVINO™ Toolkit Components

Intel® Distribution of OpenVINO™ toolkit includes the following components:

For building the Inference Engine from the source code, see the build instructions.

Installation Guides

Before installation review the Target System Platform requirements before installation. Install OpenVINO™ and configure the third-party dependencies based on your preference.

OS Based:

Install OpenVINO™Runtime on Linux, Windows, MacOS, or Raspbian OS

Install from Images or Repositories:

To install from Anaconda Cloud, APT, Docker, PyPI, Yocto, or the OpenVINO™Runtime using an installer see Install and Configure Intel® Distribution of OpenVINO™ toolkit for Linux

Get Started with OpenVINO™ Model Zoo

The Open Model Zoo in the Intel® Distribution of OpenVINO™ includes optimized deep learning models and a set of demos for developing high-performance deep learning inference applications. You can use free pre-trained models to speed-up development and deployment. To check the currently available models, use the Model Downloader. It is a set of python scripts for browsing and downloading these pre-trained models. Other automation tools are also available:

  • downloader.py (model downloader) downloads model files from online sources and, if necessary, patches them to make them more usable with Model Optimizer.
  • converter.py (model converter) converts the models that are not in the Inference Engine (IR) format into that format using Model Optimizer.
  • quantizer.py (model quantizer) quantizes full-precision models in the IR format into low-precision versions using Post-Training Optimization Toolkit.
  • info_dumper.py (model information dumper) prints information about the models in a stable machine-readable format

Use the following instructions to run downloader.py. This example runs on a Linux* machine with source installation.

python3 /opt/intel/openvino_2021/deployment_tools/open_model_zoo/tools/downloader/downloader.py --help

usage: downloader.py [-h] [--name PAT[,PAT...]] [--list FILE.LST] [--all]

[--print_all] [--precisions PREC[,PREC...]] [-o DIR]
[--cache_dir DIR] [--num_attempts N]
[--progress_format {text,json}] [-j N]

optional arguments:
--help show this help message and exit
--name PAT[,PAT...] download only models whose names match at least one ofspecified patterns
--list FILE.LST download only models whose names match at least one ofpatterns in the specified file
--all  download all available models
--print_all print all available models
--precisions PREC[,PREC...]

download only models with the specified precisions:
(actual for DLDT networks)

-o DIR, --output_dir DIR

path for saving models:
--cache_dir DIR directory to use as a cache for downloaded files
--num_attempts N attempt each download up to N times
--progress_format {text,json}

which format to use for progress reporting:

-j N, --jobs N how many downloads to perform concurrently</code>

Use the parameter --printall to see which pre-trained models are available for download in the current version of OpenVINO. The following example is a classic computer vision network used to detect a target picture. Download ssdmobilenetv1coco using Model Downloader.

python3 /opt/intel/openvino_2021/deployment_tools/open_model_zoo/tools/downloader/downloader.py --name ssd_mobilenet_v1_coco</code>

OpenVINO™ Model Optimizer

Model Optimizer is a cross-platform command-line tool that facilitates the transition between the training and deployment environment, performs static model analysis, and adjusts deep learning models for optimal execution on end-point target devices. For more information see the Model Optimizer Development Guide

Model Optimizer assumes you have a network model trained using a supported deep learning framework. The figure below shows the typical workflow for deploying a trained deep learning model:

Typical workflow for deploying a trained deep learning model

Figure 2. Typical workflow for deploying a trained deep learning model [2]

Network topology files are described in .xml format. Weights and biases are stored in binary format in .bin files.

To be able to convert ssdmobilenetv1coco model into IR, some model specific parameters must be provided to the Model Optimizer. A .yml file with model specific information was downloaded when thie model was downloaded from Open Model Zoo. Here is an example for ssdmobilenetv1coco:

cat /opt/intel/openvino_2021/deployment_tools/open_model_zoo/models/public/ssd_mobilenet_v1_coco/model.yml

The Model Downloader also contains another handy script 'converter.py' for accurately inputting the parameters of the downloaded model to the Model Optimizer (MO). Use this script for model conversion to reduce the workload.

python3 /opt/intel/openvino_2021/deployment_tools/open_model_zoo/tools/downloader/converter.py \
--download_dir=. \
--output_dir=. \
--name=ssd_mobilenet_v1_coco \
--dry_run

You can choose to convert the model using “converter.py” or use the Model Optimizer execution parameters that were generated by the command above and add them as input parameters shown below:

python3 /opt/intel/openvino/deployment_tools/model_optimizer/mo.py \
--framework=tf \
--data_type=FP32 \
--output_dir=public/ssd_mobilenet_v1_coco/FP32 \
--model_name=ssd_mobilenet_v1_coco \
--reverse_input_channels \
--input_shape=[1,300,300,3] \
--input=image_tensor \
--output=detection_scores,detection_boxes,num_detections \
--transformations_config=/opt/intel/openvino/deployment_tools/model_optimizer/extensions/front/tf/ssd_v2_support.json \
--tensorflow_object_detection_api_pipeline_config=public/ssd_mobilenet_v1_coco/ssd_mobilenet_v1_coco_2018_01_28/pipeline.config \
--input_model=public/ssd_mobilenet_v1_coco/ssd_mobilenet_v1_coco_2018_01_28/frozen_inference_graph.pb

Model Optimizer arguments:

Common parameters:

- Path to the Input Model:

/root/jupyter_root/public/ssd_mobilenet_v1_coco/ssd_mobilenet_v1_coco_2018_01_28/frozen_inference_graph.

pb

- Path for generated IR: /root/jupyter_root/public/ssd_mobilenet_v1_coco/FP32
- IR output name: ssd_mobilenet_v1_coco
- Log level: ERROR
- Batch: Not specified, inherited from the model
- Input layers: image_tensor
- Output layers: detection_scores,detection_boxes,num_detections
- Input shapes: [1,300,300,3]
- Mean values: Not specified
- Scale values: Not specified
- Scale factor: Not specified
- Precision of IR: FP32
- Enable fusing: True
- Enable grouped convolutions fusing: True
- Move mean values to preprocess section: None
- Reverse input channels: True


TensorFlow specific parameters:

- Input model in text protobuf format: False
- Path to model dump for TensorBoard: None
- List of shared libraries with TensorFlow custom layers implementation: None
- Update the configuration file with input/output node names: None
- Use configuration file used to generate the model with Object Detection API: /root/jupyter_root/public/ssd_mobilenet_v1_coco/ssd_mobilenet_v1_coco_2018_01_28/pipeline.config
- Use the config file: None
- Inference Engine found in: /opt/intel/openvino/python/python3.6/openvino

Inference Engine version: 2.1.2021.3.0-2787-60059f2c755-releases/2021/3

Model Optimizer version: 2021.3.0-2787-60059f2c755-releases/2021/3Preprocessor block has been removed. Only nodes performing mean value subtraction and scaling (if applicable) are kept.

[ SUCCESS ] Generated IR version 10 model.
[ SUCCESS ] XML file: /root/jupyter_root/public/ssd_mobilenet_v1_coco/FP32/ssd_mobilenet_v1_coco.xml
[ SUCCESS ] BIN file: /root/jupyter_root/public/ssd_mobilenet_v1_coco/FP32/ssd_mobilenet_v1_coco.bin
[ SUCCESS ] Total execution time: 47.92 seconds.
[ SUCCESS ] Memory consumed: 455 MB.

Practice Inference Engine API

After creating intermediate representation files using the Model Optimizer, use the Inference Engine to infer the result for a given input data. The Inference Engine is a C++ library with a set of C++ classes to infer input data (images) and get a result. The C++ library provides an API to read the intermediate representation, set the input and output formats, and execute the model on devices.

The Inference Engine is a software component that contains the complete implementation for inference on various Intel® hardware devices: CPU, GPU, VPU, FPGA, etc. Each of these plugins implements the unified API along with hardware-specific APIs. The following figure show the steps of the integration process:

Integration process

Figure 3. Integration process [3]

Load Plugin

Create Inference Engine Core to manage available devices and their plugins internally.

Load Plugin

Read Model IR

Read a model IR created by the Model Optimizer.

Real Model IR

Configure Input and Output

The information about the input and output layers of the network is stored in the loaded neural network object net. Use the following two parameters to obtain the information about the ef layers and set the inference execution accuracy of the network:

  • input_info
  • outputs

Configure Input and Output

Load Model

Load the model to the device using:

  • InferenceEngine::Core::LoadNetwork()

Create Inference Request and Prepare Input

To perform a neural network inference, read the image from disk and bind it to the input blob. After loading the image, determine the size of the image and format of the layout. For example, the default layout format of OpenCV is CHW, but the original layout of the image was HWC. Modify the layout format and add the Batch size N dimension, then organize the image format according to NCHW and resize the input image to the network input size.

Inference Calls

This example uses the synchronous API to demonstrate how to perform inference, calling:

  • InferenceEngine::InferRequest::Infer()

To improve the inference performance, use the asynchronous API for inference as follows:

  • InferenceEngine::InferRequest::StartAsync()
  • InferenceEngine::InferRequest::Wait()

Inference Call

Process the Output

After the inference engine inputs the graph and performs inference, a result is generated. The result contains a list of classes (classid), confidence and bounding boxes. For each bounding box, the coordinates are given relative to the upper left and lower right corners of the original image. The correspondence between classid and the labels file allow us to parse the text corresponding to the class, which is used to facilitate human reading comprehension.

Visualization of the Inference Results

image of a horse

Figure 4. Image example

Practice Post-Training Optimization Tool (POT)

POT is designed to accelerate the inference of deep learning models by applying special methods without model retraining or fine-tuning, liked post-training quantization. Therefore, the tool does not require a training dataset or a pipeline. To apply post-training algorithms from the POT, you need:

  • A full precision model, FP32 or FP16, converted into the OpenVINO™ Intermediate Representation (IR) format

  • A representative calibration dataset of data samples representing a use case scenario, for example, 300 images

The tool is aimed to fully automate the model transformation process without changing the model structure. The POT is available only in the Intel® Distribution of OpenVINO™ toolkit. For details about the low-precision flow in OpenVINO™, see Optimizing models post-training.

Post-training Optimization Tool includes a standalone command-line tool and a Python* API that provide the following key features:

  • Two post-training 8-bit quantization algorithms: fast DefaultQuantization and precise AccuracyAwareQuantization.

  • Global optimization of post-training quantization parameters

  • Symmetric and asymmetric quantization schemes. For details, see the Quantization section.

  • Compression for different hardware targets such as CPU and GPU.

  • Per-channel quantization for Convolutional and Fully-Connected layers.

  • Multiple domains: Computer Vision, Recommendation Systems.

  • Ability to implement a custom optimization pipeline via the supported API.

Before we start using the POT tool, we will need to prepare some config files:

  • dataset files

  • dataset definitions file: dataset_definitions.yml

  • model json config for POT: ssdmobilenetv1int8.json

  • model accuracy checker config: ssdmobilenetv1_coco.yml

Dataset Preparation

This example shows the dataset of Common Objects in Context (COCO). The model was trained with this dataset. Prepare the dataset according to Dataset Preparation Guide.

Download COCO dataset:

Global Dataset Configuration

If you want to use the definitions file in quantization via Post Training Optimization Toolkit (POT), input the correct file path in these fields in the global dataset configuration file:

  • annotationfile: [PATHTODATASET]/instancesval2017.json
  • datasource: [PATHTO_DATASET]/val2017

Prepare Model Quantization and Configuration

Create two config files. One to include model specific and another for the dataset specific configurations.

  • ssdmobilenetv1int8.json
  • ssdmobilenetv1_coco.yml
  1. Create a new file and name it ssdmobilenetv1int8.json. This is the POT configuration file.

  1. Create a dataset config file and name it ssdmobilenetv1_coco.yml

Quantize the Model

Run the Accuracy checker tool and POT tool to create your quantized IR files.

Compare FP32 and INT8 Model Performance

This demonstrates how to run the Benchmark Python* Tool, which performs inference using convolutional networks. Performance can be measured for two inference modes: synchronous (latency-oriented) and asynchronous (throughput-oriented).

Upon start-up, the application reads command-line parameters and loads a network and images/binary files to the Inference Engine plugin, which is chosen depending on a specified device. The number of infer requests and execution approach depend on the mode defined with the -api command-line parameter. For more information see OpenVINO™ Inference Engine Tools Benchmark Tool README

Please run both of your FP32 and INT8 models on Benchmark Python* Tool and compare your results.

Now that you have run both your FP32 and INT8 IRs, you can make a comparison of the performance gain you are achieving with INT8 IR files. See the official benchmark results for Intel® Distribution of OpenVINO™ Toolkit on various Intel® hardware settings.

Conclusion

This guide provides recommendations for tuning The Intel® Distribution of OpenVINO™ Toolkit using the power of vector neural network instructions (VNNI) and Intel® Advanced Vector Extensions (AVX512) with low precision inference workloads. You can use the steps and code to modify similar types of workloads so that you see a performance boost. Check out the this official benchmark result page for more examples.

Additional Information

References

[1] Typical OpenVINO™ workflow from https://docs.openvinotoolkit.org/latest/index.html#openvinotoolkitcomponents on 8/4/21

[2] Typical workflow for deploying a trained deep learning model from https://docs.openvinotoolkit.org/2021.3/openvinodocsMODGDeepLearningModelOptimizerDevGuide.html on 8/5/21

[3] Integration process from https://docs.openvinotoolkit.org/latest/openvinodocsIEDGDeepLearningInferenceEngineDevGuide.html on 8/5/21

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.