core/docs/usecase2.md

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# Copyright (c) 2019-2020, NVIDIA CORPORATION.  All rights reserved.

@page core_usecase2 System and Platform Information
@tableofcontents

@note SW Release Applicability: This tutorial is applicable to modules in both **NVIDIA DriveWorks** and **NVIDIA DRIVE Software** releases.

@section core_platforminfo_gpu GPU Enumeration and Selection

On NVIDIA DRIVE<sup>&trade;</sup> systems, multiple GPUs are present and available for the SDK.
- Integrated GPU (iGPU) is a GPU that shares the same die as the
  ARM CPU.
- Descrete GPU (dGPU) is a separate unit connected over a PCIEX bus with
  the main CPU.

At runtime, user applications can enumerate and select
these GPUs. Most of the NVIDIA<sup>&reg;</sup> DriveWorks modules use the currently selected GPU.

```{.cpp}
#include <dw/core/Context.h>

...

// enumerate all available GPUs in the system and select first available dGPU
int32_t numGPUs = 0;
dwContext_getGPUCount(&numGPUs, sdkContext);
for (int32_t i=0; i < numGPUsl; i++)
{
    dwGPUDeviceType type;
    dwContext_getGPUDeviceType(&type, i, sdkContext);
    switch (type)
    {
        case DW_GPU_DEVICE_DISCRETE:
            printf("GPU %d is a dGPU, set it as current GPU\n", i);

            dwContext_selectGPUDevice(i, sdkContext);

            break;

        case DW_GPU_DEVICE_INTEGRATED:
            printf("GPU %d is an iGPU\n", i);
            break;

        default:
    }
}

```

@note For applications that require access to GPU memory, ensure that such applications use the correct GPU.

@section core_platforminfo_dla DLA Engine Selection (Xavier SoC)

NVIDIA DRIVE<sup>&trade;</sup> platforms with the NVIDIA Xavier SoC provide
a hardware-accelerated deep learning accelerator (DLA). DLA
accelerates inferencing of the networks, which frees up
NVIDIA<sup>&reg;</sup> CUDA<sup>&reg;</sup> units to perform
other tasks.

The following snippet shows how to activate a specific DLA engine for inferencing of DriveNet. For a full sample,
see @ref dwx_drivenet_sample.

```{.cpp}

// check if current platform supports DLA engine
int32_t numDLAs = 0;
dwContext_getDLAEngineCount(&numDLAs, sdkContext);
if (numDLAs == 0)
{
    printf("The platform does not support DLA engine\n");
    return 0;
}

// setup DriveNet to use DLA engine for inferencing
dwDriveNetParams driveNetParams = {};
...
driveNetParams.processorType = DW_PROCESSOR_TYPE_DLA_0;

// DLA supports only FP16 precision
driveNetParams.networkPrecision = DW_PRECISION_FP16;

dwDriveNet_initialize(&driveNet, ..., &driveNetParams, sdkContext);
```