Update producer_consumer1.cpp

I thought this might make a good testbed for reporting a problem with debugging threads in an IDE.
The print() function with mutex makes it print cleanly.

Author: daveyostcom

Concurrency/Queue/producer_consumer1.cpp

@@ -6,18 +6,34 @@
 
 #include "Queue.h"
 #include <iostream>
+#include <sstream>
+
+const int nbConsumers = 4;
+const int nbToConsume = 3;
+const int nbToProduce = nbToConsume * nbConsumers;
+
+void print(std::string x) {
+  static std::mutex mutex;
+  std::unique_lock<std::mutex> locker(mutex);
+  std::cout << x << "\n";
+}
+
 
 void produce(Queue<int>& q) {
-  for (int i = 0; i< 10000; ++i) {
-    std::cout << "Pushing " << i << "\n";
+  for (int i = 1; i <= nbToProduce; ++i) {
+    std::ostringstream tmp;
+    tmp << "--> " << i;
+    print(tmp.str());
     q.push(i);
   }
 }
 
 void consume(Queue<int>& q, unsigned int id) {
-  for (int i = 0; i< 2500; ++i) {
+  for (int i = 0; i < nbToConsume; ++i) {
     auto item = q.pop();
-    std::cout << "Consumer " << id << " popped " << item << "\n";
+    std::ostringstream tmp;
+    tmp << "        " << item << " --> C" << id;
+    print(tmp.str());
   }
 }
 
@@ -26,21 +42,20 @@ int main()
 {
   Queue<int> q;
 
-  using namespace std::placeholders;
-
-  // producer thread
+  // Start the producer thread.
   std::thread prod1(std::bind(produce, std::ref(q)));
 
-  // consumer threads
-  std::thread consumer1(std::bind(&consume, std::ref(q), 1));
-  std::thread consumer2(std::bind(&consume, std::ref(q), 2));
-  std::thread consumer3(std::bind(&consume, std::ref(q), 3));
-  std::thread consumer4(std::bind(&consume, std::ref(q), 4));
+  // Start the consumer threads.
+  std::vector<std::thread> consumers;
+  for (int i = 0 ; i < nbConsumers ; ++i) {
+    std::thread consumer(std::bind(&consume, std::ref(q), i + 1));
+    consumers.push_back(std::move(consumer));
+  }
 
   prod1.join();
-  consumer1.join();
-  consumer2.join();
-  consumer3.join();
-  consumer4.join();
+
+  for (auto& consumer : consumers) {
+    consumer.join();
+  }
 
 }