Next Steps

Next Steps#

After installing oneTBB, complete the following steps to start working with the library.

Set the Environment Variables#

After installing oneTBB, set the environment variables:

  1. Go to the oneTBB installation directory.

  2. Set the environment variables using the script in <install_dir> by running:

    • On Linux* OS: vars.{sh|csh} in <install_dir>/tbb/latest/env

    • On Windows* OS: vars.bat in <install_dir>/tbb/latest/env

Tip

oneTBB can coordinate with Intel(R) OpenMP on CPU resources usage to avoid excessive oversubscription when both runtimes are used within a process. To enable this feature set up TCM_ENABLE environment variable to 1.

Build and Run a Sample#

  1. Create a new C++ project using your IDE. In this example, Microsoft* Visual Studio* Code is used.

  2. Create an example.cpp file in the project.

  3. Copy and paste the code below. It is a typical example of a oneTBB algorithm. The sample calculates a sum of all integer numbers from 1 to 100.

    #include <oneapi/tbb.h>

int main (){
    int sum = oneapi::tbb::parallel_reduce(
        oneapi::tbb::blocked_range<int>(1,101), 0,
        [](oneapi::tbb::blocked_range<int> const& r, int init) -> int {
            for (int v = r.begin(); v != r.end(); v++) {
                init += v;
            }
            return init;
        },
        [](int lhs, int rhs) -> int {
            return lhs + rhs;
        }
    );

    printf("Sum: %d\n", sum);
    return 0;
}

  4. Open the tasks.json file in the .vscode directory and paste the following lines to the args array:

    • -Ipath/to/oneTBB/include to add oneTBB include directory.

    • path/to/oneTBB/ to add oneTBB.

    For example:

    {
   "tasks": [
        {
           "label": "build & run",
           "type": "cppbuild",
           "group": {
           "args": [
               "/IC:\\Program Files (x86)\\Intel\\oneAPI\\tbb\\2021.9.0\\include",
               "C:\\Program Files (x86)\\Intel\\oneAPI\\tbb\\2021.9.0\\lib\\ia32\\vc14\\tbb12.lib"

  5. Build the project.

  6. Run the example.

  7. If oneTBB is configured correctly, the output displays Sum: 5050.

Hybrid CPU and NUMA Support#

If you need NUMA/Hybrid CPU support in oneTBB, you need to make sure that HWLOC* is installed on your system.

HWLOC* (Hardware Locality) is a library that provides a portable abstraction of the hierarchical topology of modern architectures (NUMA, hybrid CPU systems, etc). oneTBB relies on HWLOC* to identify the underlying topology of the system to optimize thread scheduling and memory allocation.

Without HWLOC*, oneTBB may not take advantage of NUMA/Hybrid CPU support. Therefore, it’s important to make sure that HWLOC* is installed before using oneTBB on such systems.

Check HWLOC* on the System#

To check if HWLOC* is already installed on your system, run hwloc-ls:

  • For Linux* OS, in the command line.

  • For Windows* OS, in the command prompt.

If HWLOC* is installed, the command displays information about the hardware topology of your system. If it is not installed, you receive an error message saying that the command hwloc-ls could not be found.

Note

For Hybrid CPU support, make sure that HWLOC* is version 2.5 or higher. For NUMA support, install HWLOC* version 1.11 or higher.

Install HWLOC*#

To install HWLOC*, visit the official Portable Hardware Locality website (https://www-lb.open-mpi.org/projects/hwloc/).

  • For Windows* OS, binaries are available for download.

  • For Linux* OS, only the source code is provided and binaries should be built.

On Linux* OS, HWLOC* can be also installed with package managers, such as APT*, YUM*, etc. To do so, run: sudo apt install hwloc.

Note

For Hybrid CPU support, make sure that HWLOC* is version 2.5 or higher. For NUMA support, install HWLOC* version 1.11 or higher.