c++ - Try-lock semaphore using standard libraries -

i'm building sokoban solver. since i'm doing depth-first search (yes, horrible idea, know) wish multithreaded.

my function recursive. therefore semaphore (like suggested here), need able attempt lock, , in case of no lock-ability proceed if nothing happened.

the semaphores supposed control whether or not new thread should initiated. since using recursive function can imagine whole lot of overhead, implement linked semaphore , wait release.

so: how try lock semaphore, skip waiting if no more semaphores available? or there better solution semaphores?

my build chain supports c++14. have boost installed, avoid third party libraries. using ubuntu 14.04.

(when have done want this, i'll have go @ ida*, focus on want achieve rather solving underlying enormous problem approach solving sokoban puzzle :-) )

so have add new method semaphore class (try)

// boost needed no more #include <condition_variable> #include <mutex>  using namespace std;  class semaphore { private:     mutex mutex_;     condition_variable condition_;     unsigned long count_;  public:     semaphore()         : count_()     {}      void notify()     {         unique_lock<mutex> lock(mutex_);         ++count_;         condition_.notify_one();     }      void wait()     {         unique_lock<mutex> lock(mutex_);         while(!count_)             condition_.wait(lock);         --count_;     }      bool try()     {         unique_lock<mutex> lock(mutex_);          if (count_)         {             --count_;             return true;         }         else         {             return false;         }     } };