openvino/docs/IE_DG/InferenceEngine_QueryAPI.md

Introduction to Inference Engine Device Query API

This section provides a high-level description of the process of querying of different device properties and configuration values. Refer to the Hello Query Device Sample sources and Multi-Device Plugin guide for example 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

InferenceEngine::Core core;
std::vector<std::string> availableDevices = ie.GetAvailableDevices();

The function returns list of available devices, for example:

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

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 HETERO device dumps .dot files with split graphs during the split stage:

InferenceEngine::Core core;
bool dumpDotFile = core.GetConfig("HETERO", HETERO_CONFIG_KEY(DUMP_GRAPH_DOT)).as<bool>();

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:

InferenceEngine::Core core;
std::string cpuDeviceName = core.GetMetric("GPU", METRIC_KEY(FULL_DEVICE_NAME)).as<std::string>();

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

NOTE: All metrics have specific 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, MYRIAD devices) can be found in corresponding plugin folders.

Query API in the ExecutableNetwork Class

GetMetric()

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

InferenceEngine::Core core;
auto exeNetwork = core.LoadNetwork(network, "CPU");
auto nireq = exeNetwork.GetMetric(METRIC_KEY(OPTIMAL_NUMBER_OF_INFER_REQUESTS)).as<unsigned int>();

Or the current temperature of MYRIAD device:

InferenceEngine::Core core;
auto exeNetwork = core.LoadNetwork(network, "MYRIAD");
float temperature = exeNetwork.GetMetric(METRIC_KEY(DEVICE_THERMAL)).as<float>();

GetConfig()

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

InferenceEngine::Core core;
auto exeNetwork = core.LoadNetwork(network, "CPU");
auto ncores = exeNetwork.GetConfig(PluginConfigParams::KEY_CPU_THREADS_NUM).as<std::string>();

SetConfig()

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