simple producer consumer in c++11 using threads

producerConsumer.cc

#include <iostream>
#include <cstdlib>
#include <thread>
#include <mutex>
#include <vector>
#include <unordered_map>
#include <queue>
#include <chrono>

using namespace std;

unsigned int prodVal    = 0;
unsigned int stopVal    = 1000;
unsigned int NProducers = 2;
unsigned int NConsumers = 5;

queue<unsigned int>  taskQueue;
unordered_map<unsigned int, unsigned int> resultMap;

mutex taskQueueMutex;
mutex resultMutex;


thread producer() {
  thread threadObj([](){
    while (prodVal < stopVal) {
      unsigned int val      = prodVal++;
      unsigned int sleepMS  = ((double) rand() / (RAND_MAX)) * 10;
      taskQueueMutex.lock();
      taskQueue.push(val);
      cout << "producer " << this_thread::get_id() << " val " << val << " sleepMS " << sleepMS << endl;
      taskQueueMutex.unlock();
      this_thread::sleep_for(chrono::milliseconds(sleepMS));
    }    
  });
  return threadObj;
}

thread consumer() {
  thread threadObj([](){
    while (1) {
      unsigned int sleepMS  = ((double) rand() / (RAND_MAX)) * 10 * (double)NConsumers/(double)NProducers;

      if (taskQueue.size() > 0) {
        taskQueueMutex.lock();
        unsigned int val      = taskQueue.front(); 
        taskQueue.pop(); 
        taskQueueMutex.unlock();

        resultMutex.lock();
        unsigned int result = val * val;
        resultMap[val] = result;
        cout << "consumer " << this_thread::get_id() << " val " << val << " result " << result << " sleepMS " << sleepMS << endl;
        resultMutex.unlock();        
      }
      else if (prodVal >= stopVal) {
        break;
      }
      this_thread::sleep_for(chrono::milliseconds(sleepMS));
    }    
  });
  return threadObj;
}

int main() {

  vector<thread> producers;
  for (unsigned int i = 0;i < NProducers;i++) {
    producers.push_back(producer());
  }
  vector<thread> consumers;
  for (unsigned int i = 0;i < NConsumers;i++) {
    consumers.push_back(consumer());
  }

  for (auto&& pThread : producers ) {
    pThread.join();
  }

  for (auto&& pThread : consumers ) {
    pThread.join();
  }


  cout << "results\n";
  for (unsigned int i = 0; i < stopVal;i++) {
    auto val = resultMap.find(i);
    if (val == resultMap.end()) {
      cout << i << ":notFound" << endl;
    }
    else {
      cout << i << ":" << resultMap[i] << endl;
    }
  }

  return 0;
}