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task_group

[scheduler.task_group]

A task_group represents concurrent execution of a group of tasks. Tasks can be dynamically added to the group while it is executing.

// Defined in header <oneapi/tbb/task_group.h>

namespace oneapi {
namespace tbb {

    class task_group {
    public:
        task_group();
        task_group(task_group_context& context);

        ~task_group();

        template<typename Func>
        void run(Func&& f);

        template<typename Func>
        task_handle defer(Func&& f);

        void run(task_handle&& h);

        template<typename Func>
        task_group_status run_and_wait(const Func& f);

        task_group_status run_and_wait(task_handle&& h);

        task_group_status wait();
        void cancel();
    };

    bool is_current_task_group_canceling();

} // namespace tbb
} // namespace oneapi

Member functions

task_group()

Constructs an empty task_group.

task_group(task_group_context &context)

Constructs an empty task_group. All tasks added into the task_group are associated with the context.

~task_group()

Destroys the task_group.

Requires: Method wait must be called before destroying a task_group, otherwise, the destructor throws an exception.

template<typename F>
task_handle defer(F &&f)

Creates a deferred task to compute f() and returns task_handle pointing to it.

The task is not scheduled for the execution until it is explicitly requested, for example, with the task_group::run method. However, the task is still added into the task_group, thus the task_group::wait method waits until the task_handle is either scheduled or destroyed.

The F type must meet the Function Objects requirements described in the [function.objects] section of the ISO C++ standard.

Returns: task_handle object pointing to a task to compute f().

template<typename Func>
void run(Func &&f)

Adds a task to compute f() and returns immediately. The Func type must meet the Function Objects requirements described in the [function.objects] section of the ISO C++ standard.

void run(task_handle &&h)

Schedules the task object pointed by the h for the execution.

Note

The failure to satisfy the following conditions leads to undefined behavior:

  • h is not empty.

  • *this is the same task_group that h is created with.

template<typename Func>
task_group_status run_and_wait(const Func &f)

Equivalent to {run(f); return wait();}. The Func type must meet the Function Objects requirements described in the [function.objects] section of the ISO C++ standard.

Returns: The status of task_group. See task_group_status.

task_group_status wait()

Waits for all tasks in the group to complete or be cancelled.

Returns: The status of task_group. See task_group_status.

void cancel()

Cancels all tasks in this task_group.

Non-member functions

bool is_current_task_group_canceling()

Returns true if an innermost task_group executing on this thread is cancelling its tasks.

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