* @brief Wait for all tasks done. * @brief This interface will pause all threads(workers) in workbranch to * relieve system's stress. *

* @brief attach a workbranch * @param br ptr (heap memory) * @return id * @note O(1) */

* @brief get set of result * @return std::vector<T> */

* @brief get number of tasks in the task queue * @return number */

* @brief start supervising a workbranch * @param wbr reference of workbranch */

* @brief get number of workers * @return number */

wait for all futures

* @brief delete one worker * @note O(1) */

* @brief add one worker * @note O(logN) */

* @brief detach workbranch by id * @param id branch's id * @return std::unique_ptr<workbranch> * @note O(n) */

* @brief Always execute callback before taking a rest * @param cb callback function */

* @brief get reference of workbranch * @param id workbranch's id * @return reference * @note O(1) */

go on supervising

* @brief suspend the supervisor * @param timeout the longest waiting time */

* @brief travel all the workbranchs and deal each of them * @param deal <void(workbranch&)> how to deal with the work branch */

thread's default loop

loop func

* @brief get ref of workbranch by id * @param id workbranch's id * @return reference of the workbranch * @note O(1) */

* @brief construct a supervisor * @param min_wokrs min nums of workers * @param max_wokrs max nums of workers * @param time_interval t

* @brief construct function * @param wks initial number of workers * @param strategy wait_strategy for workers (defaults to lowlatancy).