# Attach Flow Graph to an Arbitrary Task Arena

oneTBB `task_arena` interface provides mechanisms to guide tasks execution within the arena by setting the preferred computation units, restricting part of computation units, or limiting arena concurrency. In some cases, you may want to apply such mechanisms when a flow graph executes.

During its construction, a `graph` object attaches to the arena, in which the constructing thread occupies a slot.

This example shows how to set the most performant core type as the preferred one for a graph execution:

        std::vector<tbb::core_type_id> core_types = tbb::info::core_types();
        tbb::task_arena arena(
            tbb::task_arena::constraints{}.set_core_type(core_types.back())
        );

        arena.execute( [&]() {
            graph g;
            function_node< int > f( g, unlimited, []( int ) {
                 /*the most performant core type is defined as preferred.*/
            } );
            f.try_put(1);
            g.wait_for_all();
        } );

A `graph` object can be reattached to a different `task_arena` by calling the `graph::reset()` function. It reinitializes and reattaches the `graph` to the task arena instance, inside which the `graph::reset()` method is executed.

This example shows how to reattach existing graph to an arena with the most performant core type as the preferred one for a work execution. Whenever a task is spawned on behalf of the graph, it is spawned in the arena of a graph it is attached to, disregarding the arena of the thread that the task is spawned from:

        graph g;
        function_node< int > f( g, unlimited, []( int ) {
            /*the most performant core type is defined as preferred.*/
        } );

        std::vector<tbb::core_type_id> core_types = tbb::info::core_types();
        tbb::task_arena arena(
            tbb::task_arena::constraints{}.set_core_type(core_types.back())
        );

        arena.execute( [&]() {
            g.reset();
        } );
        f.try_put(1);
        g.wait_for_all();

See the following topics to learn more:

- Guiding Task Scheduler Execution
  - Set NUMA Node
  - Set Core Type
  - Limit The Maximum Number of Threads Simultaneously Scheduled To One Core
- Work Isolation