Attachment 311621 Details for Bug 455088 – Simple threading testcase.

Simple threading testcase.

threadit.cpp (text/plain), 3.76 KB, created by Jan Kratochvil on 2008-07-11 21:20:22 UTC

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Creator: Jan Kratochvil

Created: 2008-07-11 21:20:22 UTC

Size: 3.76 KB

patch

obsolete

>//
>//  Count the number of lines in a number of files.
>//  Illustrates use of multithreading. Note: run this program
>//  several times to see how the threads get scheduled on the system.
>//  Scheduling will be different each time since the system has lots
>//  of threads running, which we do not see and these will affect the
>//  scheduling of our program.
>//
>//  Note that, on a multiprocessor system, this program has a potential
>//  race condition to update the shared variable LINECOUNT, so we
>//  must use a mutex to make a short critical section whenever accessing
>//  this shared variable.
>//
>//  This program uses POSIX threads (pthreads)
>//
>///////////////////////////////////////////////////////////////////////
>
>#include <iostream.h>
>#include <fstream.h>
>#include <pthread.h>
>#include <sched.h>
>
>const int bufsize = 100;
>const int maxfiles = 4;
>
>void *ParseFile(void *);      // Must be void *, defined in pthread.h !
>
>int LINECOUNT = 0;
>
>/**********************************************************************/
>
>main ()
>
>{ pthread_t tid[maxfiles];;
>  int i,ret;
>
>// Create a thread for each file
>
>ret = pthread_create(&(tid[0]), NULL, ParseFile, (void*) "proc1");
>ret = pthread_create(&(tid[1]), NULL, ParseFile, (void*) "proc2");
>sleep(10);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc3");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc4");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc5");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc6");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc7");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc8");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc9");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc10");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc11");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc12");
>
>ret = pthread_create(&(tid[0]), NULL, ParseFile, (void*) "proc1");
>ret = pthread_create(&(tid[1]), NULL, ParseFile, (void*) "proc2");
>sleep(10);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc3");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc4");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc5");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc6");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc7");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc8");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc9");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc10");
>sleep(1);
>ret = pthread_create(&(tid[2]), NULL, ParseFile, (void*) "proc11");
>ret = pthread_create(&(tid[3]), NULL, ParseFile, (void*) "proc12");
>
>cout << "Parent thread waiting...\n";
>
> // If we don't wait for the threads, they will be killed
> // before they can start...
>
>for (i = 0; i < maxfiles; i++)
>   {
>   ret = pthread_join(tid[i],(void **)NULL);
>   }
>
>sleep(30);
>cout << "Parent thread continuing\n";
>cout << "Number of lines = " << LINECOUNT << endl;
>}
>
>/**********************************************************************/
>
>void *ParseFile(void *filename)
>
>{ fstream file;
>  char buffer[bufsize];
>  pthread_mutex_t mutex;
>  int ret;
>
>cout << "Trying to open " << filename << endl;
>
>file.open((char *)filename, ios::in);
>
>if (! file)
>   {
>   cerr << "Couldn't open file\n";
>   return NULL;
>   }
>
>while (!file.eof())
>   {
>   file.getline(buffer,bufsize);
>   cout << filename << ":" <<buffer << endl;
>
>   // Critical section
>   
>   ret = pthread_mutex_lock(&mutex);
>   LINECOUNT++;
>   ret = pthread_mutex_unlock(&mutex);
>   
>   // Try uncommenting this ....
>   // Yield the process, to allow next thread to be run
>   // sched_yield();
>   }
>
>file.close();
>}

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Attachments on bug 455088: 311621 | 313210