POSIX Threads (Pthreads) for 
      Shared Address Space 
        Programming
         Pthreads
         • Posix threads package
            • Available on almost all machines (portable standard)
            • Sort of like doing “parallel” (not “parallel for”) in OpenMP explicitly
         • Basic calls:
            • pthread_create: creates a thread, to execute a given function
            • Pthread_join
            • barrier, lock, mutex
            • Thread private variables
         • Many online resources:
            • E.g., https://computing.llnl.gov/tutorials/pthreads/
                                                   L.V.Kale                                      2
        Pthreads–Create and Join
        • Spawn an attached thread                           • Detached threads
        pthread_create                                           • Join is not needed
          (&thread1, NULL, foo, &arg)                            • The OS destroys thread 
                       .                                           resources when they 
                       .                                           terminate
                       .                                         • A parameter in the create 
        pthread_join(thread1, status)                              call indicates a detached 
                                                                   thread
        • Thread execution
        void foo(&arg)
        {  // Thread code
            return(*status);
        }
                                                  L.V.Kale                                     3
           Executing a Thread 
                                    Main Program 
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                                           .                                       void * func (void *arg)                d1
                                                                                                                           
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                    pthread_create(&thread1, NULL, func, &arg);                      {                                    t
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                                                                                        return (status);                  M
                            pthread_join(thread1, status);                           }                                    a
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                                                                 L.V.Kale                                                   4