# `TBB-Async-Sycl` Sample
This sample illustrates how the computational kernel can be split for execution between CPU and GPU using Intel® oneAPI Threading Building Blocks (oneTBB) Flow Graph asynchronous node and functional node.

The Flow Graph asynchronous node uses SYCL* to implement GPU calculations while the functional node does the CPU part of calculations. This `tbb-async-sycl` sample code is implemented using C++ and SYCL* for CPU and GPU.

| Optimized for                     | Description
|:---                               |:---
| OS                                | Linux* Ubuntu* 18.04 <br> Windows* 10, 11
| Hardware                          | Skylake with GEN9 or newer
| Software                          | Intel&reg; oneAPI DPC++/C++ Compiler
| What you will learn               | How to offload the computation to GPU using the Intel&reg; oneAPI DPC++/C++ Compiler
| Time to complete                  | 15 minutes

## Purpose
The purpose of this sample is to show how during execution, a computational kernel can be split between CPU and GPU using oneTBB Flow Graph asynchronous node and functional node.

## Key Implementation Details
Explains a oneTBB Flow Graph and SYCL*-compliant C++ implementation.

## Building the `TBB-Async-Sycl` Program

### Setting Environment Variables
When working with the Command Line Interface (CLI), you should configure the Intel&reg; oneAPI Toolkit using environment variables. Set up your CLI environment by sourcing the `setvars` script every time you open a new terminal window. This practice ensures your compiler, libraries, and tools are ready for development.

> **Note**: If you have not already done so, set up your CLI environment by sourcing the `setvars` script located in the root of your oneAPI installation.
>
> Linux*:
> - For system wide installations: `. /opt/intel/oneapi/setvars.sh`
> - For private installations: `. ~/intel/oneapi/setvars.sh`
> - For non-POSIX* shells, like csh, use the following command: `$ bash -c 'source <install-dir>/setvars.sh ; exec csh'`
>
> Windows*:
> - `C:\"Program Files (x86)"\Intel\oneAPI\setvars.bat`
> - For Windows PowerShell*, use the following command: `cmd.exe "/K" '"C:\Program Files (x86)\Intel\oneAPI\setvars.bat" && powershell'`
>
> Microsoft Visual Studio*:
> - Open a command prompt window and execute `setx SETVARS_CONFIG " "`. This only needs to be set once and will automatically execute the `setvars` script every time Visual Studio is launched.
>
>For more information on environment variables, see "Use the setvars Script" for [Linux or macOS](https://www.intel.com/content/www/us/en/develop/documentation/oneapi-programming-guide/top/oneapi-development-environment-setup/use-the-setvars-script-with-linux-or-macos.html), or [Windows](https://www.intel.com/content/www/us/en/develop/documentation/oneapi-programming-guide/top/oneapi-development-environment-setup/use-the-setvars-script-with-windows.html).

You can use [Modulefiles scripts](https://www.intel.com/content/www/us/en/develop/documentation/oneapi-programming-guide/top/oneapi-development-environment-setup/use-modulefiles-with-linux.html) to set up your development environment. The modulefiles scripts work with all Linux shells.

If you wish to fine tune the list of components and the version of those components, use
a [setvars config file](https://www.intel.com/content/www/us/en/develop/documentation/oneapi-programming-guide/top/oneapi-development-environment-setup/use-the-setvars-script-with-linux-or-macos/use-a-config-file-for-setvars-sh-on-linux-or-macos.html) to set up your development environment.

## Using Visual Studio Code* (Optional)

You can use Visual Studio Code (VS Code*) extensions to set your environment, create launch configurations, and browse and download samples.

The basic steps to build and run a sample using VS Code include:
 - Download a sample using the extension **Code Sample Browser for Intel&reg; Software Development Tools**.
 - Configure the oneAPI environment with the extension **Environment Configurator for Intel&reg; Software Development Tools**.
 - Open a Terminal in VS Code (**Terminal>New Terminal**).
 - Run the sample in the VS Code terminal using the instructions below.
 - (Linux only) Debug your GPU application with GDB for Intel&reg; oneAPI Toolkits using the **Generate Launch Configurations** extension.

To learn more about the extensions, see the
[Using Visual Studio Code* to Develop Intel® oneAPI Applications](https://www.intel.com/content/www/us/en/develop/documentation/using-vs-code-with-intel-oneapi/top.html).

### On a Linux System
* Build tbb-async-sycl program
  ```
  cd tbb-async-sycl &&
  mkdir build &&
  cd build &&
  cmake .. &&
  make VERBOSE=1
  ```

* Run the program
  ```
  make run
  ```

* Clean the program
  ```
  make clean
  ```

## Running the Sample

### Example of Output

```
start index for GPU = 0; end index for GPU = 8
start index for CPU = 8; end index for CPU = 16
Heterogeneous triad correct.
c_array: 0 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5
c_gold : 0 1.5 3 4.5 6 7.5 9 10.5 12 13.5 15 16.5 18 19.5 21 22.5
Built target run
```

### Troubleshooting
If an error occurs, troubleshoot the problem using the Diagnostics Utility for oneAPI.
[Learn more](https://www.intel.com/content/www/us/en/develop/documentation/diagnostic-utility-user-guide/top.html).