Producer consumer problem

This is a discussion on Producer consumer problem within the C Programming forums, part of the General Programming Boards category; Code: /* prodcons3.c is an implementation of the bounded buffer producer consumer problem. In this implementation there may be any ...

  1. #1
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    Sep 2002
    Posts
    6

    Producer consumer problem

    Code:
    /* prodcons3.c is an implementation of the bounded buffer producer consumer
       problem.  In this implementation there may be any number of producers and
       any number of consumers.  The program is run with three arguments: (1) the number 
       of items to be placed in the buffer,  (2) the number of producers who will
       create the items (3) number of consumers. 
    #include        <pthread.h> 
    #include        <semaphore.h>
    #include        <sys/time.h>    /* timeval{} for select() */
    #include        <stdio.h>
    #include        <stdlib.h>
    
    #define NBUFF            10
    #define MAXNTHREADS     100
    
    int nitems, nproducers;         /* read-only by producer and consumer */
    
    struct
    {                               /* data shared by producers and consumer */
      int buff[NBUFF];
      int nput;
      int nputval;
      sem_t mutex, nempty, nstored; /* semaphores, not pointers */
    }
    shared;
    
    void *produce (void *), *consume (void *);
    
    int
    main (int argc, char **argv)
    {
      int i, pcount[MAXNTHREADS];
      pthread_t tid_produce[MAXNTHREADS], tid_consume;
    
      if (argc != 3)
        {
          printf ("Invalid no. of arguments. Need nitems and nproducers. \n");
          exit (3);
        };
    
      nitems = atoi (argv[1]);
    
      nproducers = min (atoi (argv[2]), MAXNTHREADS);
    
      /* initialize three semaphores */
      sem_init (&shared.mutex, 0, 1);
      sem_init (&shared.nempty, 0, NBUFF);
      sem_init (&shared.nstored, 0, 0);
    
      /* create all producers and one consumer */
      for (i = 0; i < nproducers; i++)
        {
          pcount[i] = 0;
          pthread_create (&tid_produce[i], NULL, produce, &pcount[i]);
        }
      pthread_create (&tid_consume, NULL, consume, NULL);
    
      /* wait for all producers and the consumer */
      for (i = 0; i < nproducers; i++)
          pthread_join (tid_produce[i], NULL);
      pthread_join (tid_consume, NULL);
    
      printf ("\n Number of buffer items contributed by each thread: \n");
      for (i = 0; i < nproducers; i++)
          printf ("pcount[%d] = %d\n", i, pcount[i]);
      sem_destroy (&shared.mutex);
      sem_destroy (&shared.nempty);
      sem_destroy (&shared.nstored);
      exit (0);
    }
    /* end main */
    
    /* include produce */
    void *
    produce (void *arg)
    {
      for (;;)
        {
          sem_wait (&shared.nempty);        /* wait for at least 1 empty slot */
          sem_wait (&shared.mutex);
    
          if (shared.nput >= nitems)
            {
              sem_post (&shared.nempty);
              sem_post (&shared.mutex);
              return (NULL);        /* all done */
            }
          shared.buff[shared.nput % NBUFF] = shared.nputval;
          printf ("p:%d ", shared.nputval);
          shared.nput++;
          shared.nputval++;
          sem_post (&shared.mutex);
          sem_post (&shared.nstored);       /* 1 more stored item */
          *((int *) arg) += 1;   /*increment count of items contributed by this thread. */
        }
    }
    /* end produce */
    
    /* include consume */
    void *
    consume (void *arg)
    {
      int i;
    
      for (i = 0; i < nitems; i++)
        {
          sem_wait (&shared.nstored);       /* wait for at least 1 stored item */
          sem_wait (&shared.mutex);
          if (shared.buff[i % NBUFF] != i)
            printf ("error: buff[%d] = %d\n", i, shared.buff[i % NBUFF]);
          printf ("c:%d ", shared.buff[i % NBUFF]);
          sem_post (&shared.mutex);
          sem_post (&shared.nempty);        /* 1 more empty slot */
        }
      return (NULL);
    }
    /* end consume */
    int
    min (int a, int b)
    {
      if (a < b)
        return a;
      else
        return b;
    }
    
     i got this to work for only 1 consumer but im having trouble , cause it wont work when i specify the number of  consumers as a parameter please help
    
    my script file
    
    # Compile the producer consumer program.
    gcc -c prodcons3.c
    
    # Link the program using the POSIX C threads library
    gcc  -D_REENTRANT -lpthread -o prodcons3 prodcons3.o
    
    # Run the program. The first parameter is the number of items.
    # The second is the number of producer processes.  In prodcons2 there
    # is only one consumer process.
    ./prodcons2 500 10 10

    &#91;code]&#91;/code]tagged by Salem
    Last edited by traz; 11-08-2002 at 02:13 PM.

  2. #2
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    Sep 2002
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    6

    update

    UPDATED CODE
    Code:
    #include        <pthread.h> 
    #include        <semaphore.h>
    #include        <sys/time.h>    /* timeval{} for select() */
    #include        <stdio.h>
    #include        <stdlib.h>
    
    #define NBUFF            10
    #define MAXNTHREADS     100
    
    int nitems, nproducers, nconsumers;         /* read-only by producer and consumer */
    
    struct
    {                               /* data shared by producers and consumer */
      int buff[NBUFF];
      int nput;
      int nputval;
      sem_t mutex, nempty, nstored; /* semaphores, not pointers */
    }
    shared;
    
    void *produce (void *), *consume (void *);
    
    int
    main (int argc, char **argv)
    {
      int i,ccount[MAXNTHREADS], pcount[MAXNTHREADS];
      pthread_t tid_consume[MAXNTHREADS],tid_produce[MAXNTHREADS] ;
    
      if (argc != 4)
        {
          printf ("Invalid no. of arguments. Need nitems and nproducers. \n");
          exit (3);
        };
    
      nitems = atoi (argv[1]);
    
      nproducers = min (atoi (argv[2]), MAXNTHREADS);
      nconsumers = min (atoi(argv[3]), MAXNTHREADS);
      /* initialize three semaphores */
      sem_init (&shared.mutex, 0, 1);
      sem_init (&shared.nempty, 0, NBUFF);
      sem_init (&shared.nstored, 0, 0);
    
      /* create all producers  */
      for (i = 0; i < nproducers; i++)
        {
          pcount[i] = 0;
          pthread_create (&tid_produce[i], NULL, produce, &pcount[i]);
        }
      /*create multipul consumers*/
      for (i = 0; i < nconsumers; i++)
        {
          ccount[i] = 0;
          pthread_create (&tid_consume[i], NULL, consume, &ccount[i]);
        }
       
    
      /* wait for all producers and the consumer */
      for (i = 0; i < nproducers; i++)
          pthread_join (tid_produce[i], NULL);
      for (i = 0; i < nconsumers; i++)   
          pthread_join (tid_consume[i], NULL);
    
      printf ("\n Number of buffer items contributed by each thread: \n");
      for (i = 0; i < nproducers; i++)
          printf ("pcount[%d] = %d\n", i, pcount[i]);
         
          
       for (i = 0; i < nconsumers; i++)
          printf ("ccount[%d] = %d\n", i, ccount[i]);
         
      sem_destroy (&shared.mutex);
      sem_destroy (&shared.nempty);
      sem_destroy (&shared.nstored);
      exit (0);
    }
    /* end main */
    
    /* include produce */
    void *
    produce (void *arg)
    {
      for (;;)
        {
          sem_wait (&shared.nempty);        /* wait for at least 1 empty slot */
          sem_wait (&shared.mutex);
    
          if (shared.nput >= nitems)
            {
              sem_post (&shared.nempty);
              sem_post (&shared.mutex);
              return (NULL);        /* all done */
            }
          shared.buff[shared.nput % NBUFF] = shared.nputval;
          printf ("p:%d ", shared.nputval);
          shared.nput++;
          shared.nputval++;
          sem_post (&shared.mutex);
          sem_post (&shared.nstored);       /* 1 more stored item */
          *((int *) arg) += 1;   /*increment count of items contributed by this thread. */
        }
    }
    /* end produce */
    
    /* include consume */
    void *
    consume (void *arg)
    {
      int i;
    
      for (i = 0; i < nitems; i++)
         //for(;;)
        {
          sem_wait (&shared.nstored);       /* wait for at least 1 stored item */
          sem_wait (&shared.mutex);
          if (shared.buff[i % NBUFF] != i)
            printf ("error: buff[%d] = %d\n", i, shared.buff[i % NBUFF]);
          printf ("c:%d ", shared.buff[i % NBUFF]);
          sem_post (&shared.mutex);
          sem_post (&shared.nempty);        /* 1 more empty slot */
        }
      return (NULL);
    }
    /* end consume */
    int
    min (int a, int b)
    {
      if (a < b)
        return a;
      else
        return b;
    }

  3. #3
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    What exactly is your question again?
    When all else fails, read the instructions.
    If you're posting code, use code tags: [code] /* insert code here */ [/code]

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