Implementation of simple lock free bounded queue in C++

lock_free_bounded_queue.cpp

#include <atomic>
#include <chrono>
#include <cinttypes>
#include <cstdio>
#include <thread>
using namespace std;

#define NUM_PRODUCER                4
#define NUM_CONSUMER                NUM_PRODUCER
#define NUM_THREADS                 (NUM_PRODUCER + NUM_CONSUMER)
#define NUM_ENQUEUE_PER_PRODUCER    10000000
#define NUM_DEQUEUE_PER_CONSUMER    NUM_ENQUEUE_PER_PRODUCER

#define QUEUE_SIZE      1024

typedef struct QueueNode {
    int key;
    uint64_t flag;
} QueueNode;

class Queue {
private:
  struct QueueNode *slot;
  uint64_t size;
  atomic<uint64_t> front;
  atomic<uint64_t> rear;

public:
  Queue(uint64_t _size) : slot(new QueueNode[_size]), size(_size), front(0), rear(0) {}

  void enqueue(int key) {
    uint64_t cur_slot = rear++;
    int order = cur_slot / size;
    cur_slot = cur_slot % size;

    while (true) {
      uint64_t flag = slot[cur_slot].flag;
      if (flag % 2 == 1 || flag / 2 != order) {
        this_thread::yield();
      } else {
        slot[cur_slot].key = key;
        slot[cur_slot].flag++;
        break;
      }
    }
  }

  int dequeue() {
    uint64_t cur_slot = front++;
    int order = cur_slot / size;
    cur_slot = cur_slot % size;

    while (true) {
      uint64_t flag = slot[cur_slot].flag;
      if (flag % 2 == 0 || flag / 2 != order) {
        this_thread::yield();
      } else {
        int ret = slot[cur_slot].key;
        slot[cur_slot].flag++;
        return ret;
      }
    }
  }

  ~Queue() {
    delete[] slot;
  }
};

bool flag_verification[NUM_PRODUCER * NUM_ENQUEUE_PER_PRODUCER];
Queue queue(QUEUE_SIZE);

void ProducerFunc(int tid) {
    int key_enqueue = NUM_ENQUEUE_PER_PRODUCER * tid;
    for (int i = 0; i < NUM_ENQUEUE_PER_PRODUCER; i++) {
        queue.enqueue(key_enqueue);
        key_enqueue++;
    }

    return;
}

void ConsumerFunc() {
    for (int i = 0; i < NUM_DEQUEUE_PER_CONSUMER; i++) {
        int key_dequeue = queue.dequeue();
        flag_verification[key_dequeue] = true;
    }

    return;
}

int main(void) {
    std::thread threads[NUM_THREADS];

    for (int i = 0; i < NUM_THREADS; i++) {
        if (i < NUM_PRODUCER) {
            threads[i] = std::thread(ProducerFunc, i);
        } else {
            threads[i] = std::thread(ConsumerFunc);
        }
    }

    for (int i = 0; i < NUM_THREADS; i++) {
        threads[i].join();
    }

    // verify
    for (int i = 0; i < NUM_PRODUCER * NUM_ENQUEUE_PER_PRODUCER; i++) {
        if (flag_verification[i] == false) {
            printf("INCORRECT!\n");
            return 0;
        }
    }
    printf("CORRECT!\n");

    return 0;
}