.. _next_steps:

Next Steps

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

Set the Environment Variables

After installing |short_name|, set the environment variables:

#. Go to the oneTBB installation directory.

#. 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

.. tab-set::

.. tab-item:: Windows* OS

    #. Create a new C++ project using your IDE. In this example, Microsoft* Visual Studio* Code is used. 
    #. Create an ``example.cpp`` file in the project. 
    #. Copy and paste the code below. It is a typical example of a |short_name| algorithm. The sample calculates a sum of all integer numbers from 1 to 100. 

       .. code:: 

          #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;
          }
  
    #. 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:

       .. code-block::

              { 
                 "tasks": [
                      {
                         "label": "build & run",
                         "type": "cppbuild",
                         "group": {
                         "args": [ 
                             "/IC:\\Program Files (x86)\\Intel\\oneAPI\\tbb\\2022.0.0\\include",
                             "C:\\Program Files (x86)\\Intel\\oneAPI\\tbb\\2022.0.0\\lib\\tbb12.lib"
                       

    #. Build the project. 
    #. Run the example. 
    #. If oneTBB is configured correctly, the output displays ``Sum: 5050``.  

.. tab-item:: Linux* OS

    #. Create an ``example.cpp`` file in the project. 
    #. Copy and paste the code below. It is a typical example of a |short_name| algorithm. The sample calculates a sum of all integer numbers from 1 to 100. 
     
       .. code:: 

          #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;
          }

    #. Compile the code using oneTBB. For example, 

       .. code-block:: 

              g++ -std=c++11 example.cpp -o example -ltbb

  
    #. Run the executable:

       .. code-block:: 

              ./example
  
    #. 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.