# condition\_variable

***

**1. Producer-Consumer Problem:**

```cpp
std::mutex m;
std::condition_variable cv;
bool data_ready = false;

void producer() {
  while (true) {
    std::lock_guard<std::mutex> lock(m);
    data_ready = true;
    cv.notify_one();
  }
}

void consumer() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return data_ready; });
    // Consume data
    data_ready = false;
  }
}
```

**2. Task Scheduler:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<Task> tasks;

void task_scheduler() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !tasks.empty(); });
    // Execute task
    tasks.pop();
  }
}
```

**3. Thread Synchronization:**

```cpp
std::mutex m;
std::condition_variable cv;
bool thread_ready = false;

void thread_1() {
  // Perform some task
  std::unique_lock<std::mutex> lock(m);
  thread_ready = true;
  cv.notify_one();
}

void thread_2() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return thread_ready; });
  // Proceed with execution
}
```

**4. Database Access:**

```cpp
std::mutex m;
std::condition_variable cv;
bool database_locked = false;

void database_access() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return !database_locked; });
  // Access database
  database_locked = true;
  lock.unlock();
  // ... perform database operations ...
  lock.lock();
  database_locked = false;
  cv.notify_one();
}
```

**5. Event Signaling:**

```cpp
std::mutex m;
std::condition_variable cv;
bool event_triggered = false;

void event_trigger() {
  std::lock_guard<std::mutex> lock(m);
  event_triggered = true;
  cv.notify_one();
}

void event_listener() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return event_triggered; });
  // Process event
}
```

**6. Suspend and Resume Threads:**

```cpp
std::mutex m;
std::condition_variable cv;
bool thread_suspended = false;

void suspend_thread() {
  std::unique_lock<std::mutex> lock(m);
  thread_suspended = true;
}

void resume_thread() {
  std::unique_lock<std::mutex> lock(m);
  thread_suspended = false;
  cv.notify_one();
}

void thread_function() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !thread_suspended; });
    // Perform some task
  }
}
```

**7. Timed Waiting:**

```cpp
std::mutex m;
std::condition_variable cv;

void wait_for(std::chrono::milliseconds timeout) {
  std::unique_lock<std::mutex> lock(m);
  cv.wait_for(lock, timeout, [] { return false; });
  // Timeout occurred
}
```

**8. Termination Notification:**

```cpp
std::mutex m;
std::condition_variable cv;
bool terminated = false;

void signal_termination() {
  std::lock_guard<std::mutex> lock(m);
  terminated = true;
  cv.notify_all();
}

void wait_for_termination() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return terminated; });
  // Termination acknowledged
}
```

**9. Resource Pooling:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<Resource> resources;

Resource acquire_resource() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return !resources.empty(); });
  Resource resource = resources.front();
  resources.pop();
  return resource;
}

void release_resource(Resource resource) {
  std::unique_lock<std::mutex> lock(m);
  resources.push(resource);
  cv.notify_one();
}
```

**10. Data Structures Synchronization:**

```cpp
std::mutex m;
std::condition_variable cv;
std::list<int> list;

void insert_element(int element) {
  std::lock_guard<std::mutex> lock(m);
  list.push_back(element);
  cv.notify_one();
}

bool has_element() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return !list.empty(); });
  return true;
}
```

**11. Thread Pool Management:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<std::function<void()>> tasks;

void task_processor() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !tasks.empty(); });
    std::function<void()> task = tasks.front();
    tasks.pop();
    task();
  }
}
```

**12. Data Synchronization Between Threads:**

```cpp
std::mutex m;
std::condition_variable cv;
int shared_data = 0;

void update_data(int delta) {
  std::lock_guard<std::mutex> lock(m);
  shared_data += delta;
}

int get_data() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return shared_data != 0; });
  return shared_data;
}
```

**13. Inter-Process Communication:**

```cpp
std::mutex m;
std::condition_variable cv;
bool message_received = false;

void send_message(const std::string& message) {
  std::lock_guard<std::mutex> lock(m);
  message_received = true;
  cv.notify_one();
}

void receive_message() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return message_received; });
  // Process message
}
```

**14. Multi-Threaded File Processing:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<std::string> files;

void file_processor() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !files.empty(); });
    std::string file = files.front();
    files.pop();
    // Process file
  }
}
```

**15. Concurrent Data Structures:**

```cpp
std::mutex m;
std::condition_variable cv;
std::unordered_map<int, std::string> concurrent_map;

void insert_map(int key, const std::string& value) {
  std::lock_guard<std::mutex> lock(m);
  concurrent_map[key] = value;
}

std::string get_map_value(int key) {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [key] { return concurrent_map.find(key) != concurrent_map.end(); });
  return concurrent_map[key];
}
```

**16. Network Event Handling:**

```cpp
std::mutex m;
std::condition_variable cv;
int client_connections = 0;

void handle_connection() {
  std::unique_lock<std::mutex> lock(m);
  ++client_connections;
}

void wait_for_clients() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return client_connections > 0; });
}
```

**17. WebSocket Communication:**

```cpp
std::mutex m;
std::condition_variable cv;
std::string message;

void send_websocket_message(const std::string& msg) {
  std::lock_guard<std::mutex> lock(m);
  message = msg;
  cv.notify_one();
}

void receive_websocket_message() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return !message.empty(); });
  // Process message
}
```

**18. Distributed Computing:**

```cpp
std::mutex m;
std::condition_variable cv;
std::vector<int> results;

void distributed_worker(int task) {
  // Perform computation
  int result = compute(task);
  std::lock_guard<std::mutex> lock(m);
  results.push_back(result);
  cv.notify_one();
}

void aggregate_results() {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [] { return results.size() == tasks.size(); });
  // Process results
}
```

**19. Video Streaming:**

```cpp
std::mutex m;
std::condition_variable cv;
bool new_frame_available = false;

void video_streamer() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return new_frame_available; });
    // Stream new frame
    new_frame_available = false;
  }
}
```

**20. Game Loop Synchronization:**

```cpp
std::mutex m;
std::condition_variable cv;
bool game_loop_paused = false;

void game_loop() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !game_loop_paused; });
    // Run game loop
  }
}
```

**21. Data Processing Pipeline:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<Data> data_queue;

void data_producer() {
  while (true) {
    Data data = generate_data();
    std::lock_guard<std::mutex> lock(m);
    data_queue.push(data);
    cv.notify_one();
  }
}

void data_processor() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !data_queue.empty(); });
    Data data = data_queue.front();
    data_queue.pop();
    // Process data
  }
}
```

**22. Background Task Manager:**

```cpp
std::mutex m;
std::condition_variable cv;
std::queue<Task> tasks;

void background_task_manager() {
  while (true) {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return !tasks.empty(); });
    Task task = tasks.front();
    tasks.pop();
    // Execute task
  }
}
```

**23. Concurrent Hash Table:**

```cpp
std::mutex m;
std::condition_variable cv;
std::unordered_map<int, std::string> concurrent_hash_table;

void insert_hash(int key, const std::string& value) {
  std::lock_guard<std::mutex> lock(m);
  concurrent_hash_table[key] = value;
  cv.notify_one();
}

std::string get_hash_value(int key) {
  std::unique_lock<std::mutex> lock(m);
  cv.wait(lock, [key] { return concurrent_hash_table.find(key) != concurrent_hash_table.end(); });
  return concurrent_hash_table[key];
}
```

**24. Wait-Free Queues:**

```cpp
std::atomic<bool> empty;
std::atomic<bool> full;
std::atomic<int> head;
std::atomic<int> tail;
std::array<int, QUEUE_SIZE> queue;

void enqueue(int element) {
  while (full.load()) {}
  int next = (tail.load() + 1) % QUEUE_SIZE;
  if (next == head.load()) {
    full.store(true);
    return;
  }
  queue[tail.load()] = element;
  tail.store(next);
  empty.store(false);
}

int dequeue() {
  while (empty.load()) {}
  int next = (head.load() + 1) % QUEUE_SIZE;
  if (next == tail.load()) {
    empty.store(true);
    return -1;
  }
  int element = queue[head.load()];
  head.store(next);
  full.store(false);
  return element;
}
```

**25. Lock-Free Stack:**

```cpp
struct Node {
  int value;
  Node* next;
};

std::atomic<Node*> top;

void push(int element) {
  Node* new_node = new Node{element, nullptr};
  while (true) {
    Node* current_top = top.load();
    new_node->next = current_top;
    if (top.compare_exchange_strong(current_top, new_node)) {
      break;
    }
  }
}

int pop() {
  while (true) {
    Node* current_top = top.load();
    if (current_top == nullptr) {
      return -1;
    }
    Node* next_top = current_top->next;
    if (top.compare_exchange_strong(current_top, next_top)) {
      int value = current_top->value;
      delete current_top;
      return value;
    }
  }
}
```

**26. Concurrent Skip List:**

```cpp
struct Node {
  int value;
  std::atomic<Node*> next[LEVELS];
};

std::atomic<Node*> head = nullptr;

void insert(int element) {
  Node* new_node = new Node{element, {}};
  Node* prev[LEVELS];
  for (int level = 0; level < LEVELS; ++level) {
    prev[level] = head.load();
  }
  while (true) {
    bool found = true;
    for (int level = 0; level < LEVELS; ++level) {
      Node* next = prev[level]->next[level].load();
      while (next != nullptr && next->value < element) {
        prev[level] = next;
        next = next->next[level].load();
      }
      if (next != nullptr && next->value == element) {
        found = false;
        break;
      }
    }
    if (found) {
      for (int level = 0; level < LEVELS; ++level) {
        new_node->next[level].store(prev[level]->next[level].load());
      }
      if (prev[0].compare_exchange_strong(prev[0]->next[0], new_node)) {
        break;
      }
    }
  }
}

bool find(int element) {
  Node* prev[LEVELS];
  for (int level = 0; level < LEVELS; ++level) {
    prev[level] = head.load();
  }
  while (true) {
    bool found = true;
    for (int level = 0; level < LEVELS; ++level) {
      Node* next = prev[level]->next[level].load();
      while (next != nullptr && next->value < element) {
        prev[level] = next;
        next = next->next[level].load();
      }
      if (next != nullptr && next->value == element) {
        found = false;
        break;
      }
    }
    if (found) {
      return true;
    }
  }
  return false;

```