lock free

 #include <thread>
 #include <iostream>
 #include <mutex>
 #include <atomic>
 #include <chrono>

 using namespace std;

 #ifdef _LOCK_FREE

 atomic<int> i = ;

 void foo() {
     int count = ;
     while (count--)
     {
         i++;
     }
 }

 int main()
 {
     chrono::steady_clock::time_point start_time = chrono::steady_clock::now();

     thread thread1(foo);
     thread thread2(foo);

     thread1.join();
     thread2.join();

     cout << "i = " << i << endl;

     chrono::steady_clock::time_point end_time = chrono::steady_clock::now();
     chrono::duration<double> time_span = chrono::duration_cast<chrono::microseconds>(end_time - start_time);
     cout << "lock free elpased time: " << time_span.count() << " ms" << endl;

     system("pause");

     return ;
 }
 #endif // _LOCK_FREE

 #ifdef _MUTEX_LOCK
 int i = ;
 mutex g_mutex;

 void foo() {
     int count = ;
     while (count--)
     {
         g_mutex.lock();
         i++;
         g_mutex.unlock();
     }
 }

 int main()
 {
     chrono::steady_clock::time_point start_time = chrono::steady_clock::now();

     thread thread1(foo);
     thread thread2(foo);

     thread1.join();
     thread2.join();

     cout << "i = " << i << endl;

     chrono::steady_clock::time_point end_time = chrono::steady_clock::now();
     chrono::duration<double> time_span = chrono::duration_cast<chrono::microseconds>(end_time - start_time);
     cout << "mutex lock elpased time: " << time_span.count() << " ms" << endl;

     system("pause");

     return ;
 }
 #endif _MUTEX_LOCK