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Date:      Wed, 10 Mar 1999 21:02:56 +1000
From:      Greg Black <gjb@comkey.com.au>
To:        Wai Chan <wai@aloha.net>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: Multithreading sample 
Message-ID:  <19990310110256.16205.qmail@alpha.comkey.com.au>
In-Reply-To: <36E62FC8.73F4D37F@aloha.net>  of Tue, 09 Mar 1999 22:39:36 -1000
References:  <36E62FC8.73F4D37F@aloha.net>
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> I would appreciate it if someone could show me a simple multithreading
> program sample (c++ or c).  Thank you in advance!

Open any book on the subject and skim the first couple of
chapters.

Here's a trivial example from one such book.  I offer no comment
on its style (or on what it does, since all the books do that).
It does build and run on FreeBSD-2.2.8-R (and probably other
versions).


#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <pthread.h>

void do_one_thing(int *);
void do_another_thing(int *);
void do_wrap_up(int, int);

int r1 = 0, r2 = 0;

extern int
main(void)
{
  pthread_t       thread1, thread2;
 
  if (pthread_create(&thread1, 
		     NULL, (void *) do_one_thing, (void *) &r1) != 0)
    perror("pthread_create"), exit(1); 

  if (pthread_create(&thread2, 
		     NULL, (void *) do_another_thing, (void *) &r2) != 0)
    perror("pthread_create"), exit(1); 

  if (pthread_join(thread1, NULL) != 0)
    perror("pthread_join"), exit(1);

  if (pthread_join(thread2, NULL) != 0)
    perror("pthread_join"), exit(1);

  do_wrap_up(r1, r2);
  return 0; 
}

void do_one_thing(int *pnum_times)
{
  int		i, j, x;

  for (i = 0;  i < 4; i++) {
    printf("doing one thing\n"); 
    for (j = 0; j < 10000; j++)
      x = x + i;
    (*pnum_times)++;
  }
}

void do_another_thing(int *pnum_times)
{
  int		i, j, x;

  for (i = 0;  i < 4; i++) {
    printf("doing another \n"); 
    for (j = 0; j < 10000; j++)
      x = x + i;
    (*pnum_times)++;
  }
}

void do_wrap_up(int one_times, int another_times)
{
  int		total;

  total = one_times + another_times;
  printf("All done, one thing %d, another %d for a total of %d\n",
	 one_times, another_times, total);
}

-- 
Greg Black <gjb@acm.org>



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