[index]

#include <stdio.h>
#include <stdlib.h>
#include <thread.h>

/* compile with command line: cc myfile.c -lthread */

#define GetRandom( min, max ) ((rand() % (int)(((max) + 1) - (min))) + (min))

#define N           ( (int)100)

#define PROTECTED 0                                          /* yes==1, no==0 */

#if PROTECTED 
      mutex_t cs; 
#endif

 int counter=0;                                                   /* shared variable */

 bool wait=true;

/* simulate a two register CPU */
void CPU( void * delta) 
{ 
   register int reg1, reg2;
#if PROTECTED
               mutex_lock( &cs); /* option to lock area */
#endif

 reg1 = (int) delta;                                  /* CPU register 1 <- copy delta */
 reg2 = counter;                                      /* CPU register 2 <- copy counter */ 
 reg2 = reg2 + reg1;                                /* register-register addition */ 

 sleep(  GetRandom(0,10) );                     /* simulate random interrupts of CPU */  

  counter = reg2;                                    /* copy register to RAM */
#if PROTECTED
               mutex_unlock( &cs); /* option to unlock area */
#endif

  printf("count is %d\n", counter);
}


void CheckKey( void *dummy )         /* daemon process to look for a pressed */
{                                                     /* key, any key. */
                  _getch();
                 wait = false;
}

void main() {

int i, sum = (N*(N-1))/2;

#if PROTECTED
              mutex_init( &cs); /* setup binary semaphore */
#endif

                          /* start background thread */
thr_create(NULL, NULL, CheckKey, 0, THR_DAEMON | THR_LWP_CREATE, NULL); 

                       /* give each CPU its marching orders */
for(i=0; i<N; i++)
      thr_create(NULL,NULL, CPU, (void *) i, THR_LWP_CREATE, NULL); 

while (wait )                                 /* check if daemon has found a pressed key */
               sleep(100L);                   /* take a nap between ... */ 

printf("total should be %d, and is computed as %d\n", sum, counter);

}