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

@page dwx_hello_world Hello World Application

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

The following minimal tutorial will guide through writing and building your first NVIDIA<sup>&reg;</sup> DriveWorks based application on a Linux desktop machine.

## Coding

The first thing to do when building an application based on DriveWorks is to initialize its context:
```{.cpp}
dwContextHandle_t sdk = DW_NULL_HANDLE;
dwContextParameters sdkParams = {};
dwVersion sdkVersion;
dwGetVersion(&sdkVersion);
dwInitialize(&sdk, sdkVersion, &sdkParams);
```

The header for the context can be included as:
```{.cpp}
#include <dw/core/Context.h>
```

Now we can for example figure out how many GPUs are available on the host machine:
```{.cpp}
int32_t gpuCount;
dwContext_getGPUCount(&gpuCount, sdk);
std::cout << "Available GPUs: " << gpuCount << std::endl;
```

Last thing to do before exiting the program is to release the context:
```{.cpp}
dwRelease(&sdk);
```

For your reference this is what the full program will look like:
```{.cpp}
#include <iostream>
#include <dw/core/Context.h>

int main(int argc, char **argv)
{

    dwContextHandle_t sdk   = DW_NULL_HANDLE;

    // instantiate Driveworks SDK context
    dwContextParameters sdkParams = {};
    dwVersion sdkVersion;
    dwGetVersion(&sdkVersion);
    dwInitialize(&sdk, sdkVersion, &sdkParams);

    std::cout << "Context of Driveworks SDK successfully initialized." <<std::endl;
    std::cout << "Version: " << sdkVersion.major << "." << sdkVersion.minor << "." << sdkVersion.patch << std::endl;

    int32_t gpuCount;
    dwContext_getGPUCount(&gpuCount, sdk);
    std::cout << "Available GPUs: " << gpuCount << std::endl;

    // release Driveworks SDK context
    dwRelease(&sdk);

    return 0;
}
```

## Building and Executing

This application can be built with gcc using the following command:

        gcc -I/usr/local/driveworks/include/ -I/usr/local/cuda/include helloworld.cpp -ldriveworks -L/usr/local/driveworks/lib/ -lstdc++ -o helloworld

Afterwords when executing <b>./helloworld</b> you should get an output similiar to:

        Context of Driveworks SDK successfully initialized.
        Version: 1.0.218
        Available GPUs: 1

@note An extended version of this hello world application is provided, for more information see @ref dwx_hello_world_sample.
@note For more complex examples please refer to @ref dwx_samples_section.