.. _constraints_extensions:
task_arena::constraints extensions
======================================
.. note::
To enable this feature, set the ``TBB_PREVIEW_TASK_ARENA_CONSTRAINTS_EXTENSION`` macro to 1.
.. contents::
:local:
:depth: 1
Description
***********
These extensions allow to customize ``tbb::task_arena::constraints`` with the following properties:
* On machines with Intel® Hybrid Technology set the preferred core type for threads working within the task arena.
* Limit the maximum number of threads that can be scheduled to one core simultaneously.
API
***
Header
------
.. code:: cpp
#include <oneapi/tbb/task_arena.h>
Synopsis
--------
.. code:: cpp
namespace oneapi {
namespace tbb {
class task_arena {
public:
struct constraints {
constraints& set_numa_id(numa_node_id id);
constraints& set_max_concurrency(int maximal_concurrency);
constraints& set_core_type(core_type_id id);
constraints& set_max_threads_per_core(int threads_number);
numa_node_id numa_id = task_arena::automatic;
int max_concurrency = task_arena::automatic;
core_type_id core_type = task_arena::automatic;
int max_threads_per_core = task_arena::automatic;
}; // struct constraints
}; // class task_arena
} // namespace tbb
} // namespace oneapi
Member Functions
----------------
.. cpp:function:: constraints& set_numa_id(numa_node_id id)
Sets the ``numa_id`` field to the ``id``.
**Returns:** Reference to ``*this``.
.. cpp:function:: constraints& set_max_concurrency(int maximal_concurrency)
Sets the ``max_concurrency`` field to the ``maximal_concurrency``.
**Returns:** Reference to ``*this``.
.. cpp:function:: constraints& set_core_type(core_type_id id)
Sets the ``core_type`` field to the ``id``.
**Returns:** Reference to ``*this``.
.. cpp:function:: constraints& set_max_threads_per_core(int threads_number)
Sets the ``max_threads_per_core`` field to the ``threads_number``.
**Returns:** Reference to ``*this``.
Member Objects
--------------
.. cpp:member:: numa_node_id numa_id
An integral logical index uniquely identifying a NUMA node. All threads joining the
``task_arena`` are bound to this NUMA node.
.. note::
To obtain a valid NUMA node ID, call ``oneapi::tbb::info::numa_nodes()``.
.. cpp:member:: int max_concurrency
The maximum number of threads that can participate in work processing within the
``task_arena`` at the same time.
.. cpp:member:: core_type_id core_type
An integral logical index uniquely identifying a core type. All threads joining the
``task_arena`` are bound to this core type.
.. note::
To obtain a valid core type node ID, call ``oneapi::tbb::info::core_types()``.
.. cpp:member:: int max_threads_per_core
The maximum number of threads that can be scheduled to one core simultaneously.
See also:
* :doc:`oneapi::tbb::info namespace preview extensions <info_namespace_extensions>`
* `oneapi::tbb::task_arena specification <https://spec.oneapi.com/versions/latest/elements/oneTBB/source/task_scheduler/task_arena/task_arena_cls.html>`_
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