Update

openmp/1-intro-critical.cpp

+#include <iostream>
+#include <omp.h>
+
+
+int main(int argc, char** argv)
+{
+
+#pragma omp parallel num_threads(3)
+#pragma omp critical
+  std::cout << "Parallel region 1: tid:" << omp_get_thread_num() << std::endl;
+
+#pragma omp parallel num_threads(4)
+#pragma omp critical
+  std::cout << "Parallel region 2: tid:" << omp_get_thread_num() << std::endl;
+
+#pragma omp parallel num_threads(2)
+#pragma omp critical
+  std::cout << "Parallel region 3: tid:" << omp_get_thread_num() << std::endl;
+}
+

openmp/1-intro-mutex.cpp

+#include <iostream>
+#include <omp.h>
+
+
+int main(int argc, char** argv)
+{
+  omp_lock_t writelock;
+
+  omp_init_lock(&writelock);
+
+#pragma omp parallel num_threads(3)
+  {
+    omp_set_lock(&writelock);
+    std::cout << "Parallel region 1: tid:" << omp_get_thread_num() << std::endl;
+    omp_unset_lock(&writelock);
+  }
+  
+#pragma omp parallel num_threads(4)
+  {
+    omp_set_lock(&writelock);
+    std::cout << "Parallel region 2: tid:" << omp_get_thread_num() << std::endl;
+    omp_unset_lock(&writelock);
+  }
+    
+#pragma omp parallel num_threads(2)
+  {
+    omp_set_lock(&writelock);
+    std::cout << "Parallel region 3: tid:" << omp_get_thread_num() << std::endl;
+    omp_unset_lock(&writelock);
+  }
+}
+

openmp/1-intro.cpp

 #include <iostream>
 #include <omp.h>
 
-int main()
+
+int main(int argc, char** argv)
 {
+
 #pragma omp parallel num_threads(3)
   std::cout << "Parallel region 1: tid:" << omp_get_thread_num() << std::endl;
 
@@ -12,3 +14,4 @@ int main()
 #pragma omp parallel num_threads(2)
   std::cout << "Parallel region 3: tid:" << omp_get_thread_num() << std::endl;
 }
+