pThread mutex example in c/c++.

Following thread mutex lock example is collected from http://www.cs.cf.ac.uk/Dave/C/node32.html Mutex is used to synchronize access to the array data structure that
are shared by several threads.

#define _REENTRANT
#include <stdio.h>
#include <thread.h>

/* sample array data structure */
struct {
        mutex_t data_lock[5];
        int     int_val[5];
        float   float_val[5];
        } Data;

/* thread function */
void *Add_to_Value();

main()
{
int i;

/* initialize the mutexes and data */
for (i=0; i<5; i++) {
        mutex_init(&Data.data_lock[i], USYNC_THREAD, 0);
        Data.int_val[i] = 0;
        Data.float_val[i] = 0;
        }

/* set concurrency and create the threads */
thr_setconcurrency(4);

for (i=0; i<5; i++)
    thr_create(NULL, 0, Add_to_Value, (void *)(2*i), 0, NULL);

/* wait till all threads have finished */
for (i=0; i<5; i++)
        thr_join(0,0,0);

/* print the results */
printf("Final Values.....\n");

for (i=0; i<5; i++) {
        printf("integer value[%d] =\t%d\n", i, Data.int_val[i]);
        printf("float value[%d] =\t%.0f\n\n", i, Data.float_val[i]);
        }

return(0);
}


/* Threaded routine */
void *Add_to_Value(void *arg)
{
int inval = (int) arg;
int i;

for (i=0;i<10000;i++){
    mutex_lock(&Data.data_lock[i%5]);
       Data.int_val[i%5] += inval;
       Data.float_val[i%5] += (float) 1.5 * inval;
    mutex_unlock(&Data.data_lock[i%5]);
    }

return((void *)0);
}