openvino/docs/IE_DG/InferenceEngine_QueryAPI.md

Introduction to Inference Engine Device Query API

The Inference Engine Query API (C++)

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The OpenVINO™ toolkit supports inferencing with several types of devices (processors or accelerators). This page provides a high-level description of the process of querying device properties and configuration values at runtime. Refer to the Hello Query Device Sample sources and Multi-Device Plugin guide for examples of using the Inference Engine Query API in user applications.

Using the Inference Engine Query API in Your Code

The Inference Engine Core class provides the following API to query device information, set or get different device configuration properties:

• InferenceEngine::Core::GetAvailableDevices - Provides a list of available devices. If there are more than one instance of a specific device, the devices are enumerated with .suffix where suffix is a unique string identifier. The device name can be passed to all methods of the InferenceEngine::Core class that work with devices, for example InferenceEngine::Core::LoadNetwork.
• InferenceEngine::Core::GetMetric - Provides information about specific device. InferenceEngine::Core::GetConfig - Gets the current value of a specific configuration key.
• InferenceEngine::Core::SetConfig - Sets a new value for the configuration key.

The InferenceEngine::ExecutableNetwork class is also extended to support the Query API:

• InferenceEngine::ExecutableNetwork::GetMetric
• InferenceEngine::ExecutableNetwork::GetConfig
• InferenceEngine::ExecutableNetwork::SetConfig

Query API in the Core Class

GetAvailableDevices

@snippet snippets/InferenceEngine_QueryAPI0.cpp part0

The function returns list of available devices, for example:

MYRIAD.1.2-ma2480
MYRIAD.1.4-ma2480
FPGA.0
FPGA.1
CPU
GPU.0
GPU.1
...

Each device name can then be passed to:

• InferenceEngine::Core::LoadNetwork to load the network to a specific device
• InferenceEngine::Core::GetMetric to get common or device specific metrics
• All other methods of the Core class that accept deviceName

GetConfig()

The code below demonstrates how to understand whether the HETERO device dumps GraphViz .dot files with split graphs during the split stage:

@snippet snippets/InferenceEngine_QueryAPI1.cpp part1

For documentation about common configuration keys, refer to ie_plugin_config.hpp. Device specific configuration keys can be found in corresponding plugin folders.

GetMetric()

• To extract device properties such as available device, device name, supported configuration keys, and others, use the InferenceEngine::Core::GetMetric method:

@snippet snippets/InferenceEngine_QueryAPI2.cpp part2

A returned value appears as follows: Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz.

NOTE: All metrics have a type, which is specified during metric instantiation. The list of common device-agnostic metrics can be found in ie_plugin_config.hpp. Device specific metrics (for example, for HDDL or MYRIAD devices) can be found in corresponding plugin folders.

Query API in the ExecutableNetwork Class

GetMetric()

The method is used to get an executable network specific metric such as METRIC_KEY(OPTIMAL_NUMBER_OF_INFER_REQUESTS):

@snippet snippets/InferenceEngine_QueryAPI3.cpp part3

Or the current temperature of the MYRIAD device:

@snippet snippets/InferenceEngine_QueryAPI4.cpp part4

GetConfig()

The method is used to get information about configuration values the executable network has been created with:

@snippet snippets/InferenceEngine_QueryAPI5.cpp part5

SetConfig()

The only device that supports this method is Multi-Device.