Question

In C using the following 2 files to create a 3rd file that uses multiple threads to improve performance. Split the array into pieces and each piece is handled by a different thread. Use 8 threads. run and compile in linux.

#include <stdio.h>
#include <sys/time.h>


#define BUFFER_SIZE 4000000
int countPrime=0; 
int numbers[BUFFER_SIZE];

int isPrime(int n)
{
        int i;
        for(i=2;i<n;i++)
                if (n%i==0)
                        return 0;
        return 1;
}
int main()
{
        int i;

        // fill the buffer
        for(i=0;i<BUFFER_SIZE;i++)
                numbers[i] = (i+100)%100000;
        
        // Computation
        for(i=0;i<BUFFER_SIZE;i++)
                if (isPrime(numbers[i]))
                        countPrime++;

        printf("count of prime numbers = %d\n",countPrime);
}

and a thread posix c file

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

#define THREAD_NUM 5

int sum=0; /* this data is shared by the thread(s) */

/**
 * The thread will begin control in this function
 */
void *runner(void *param) 
{
        int i, upper = atoi(param);

        if (upper > 0) {
                for (i = 1; i <= upper; i++)
                        sum += 1;
        }
        printf("[thread %u] Done\n",pthread_self());
        pthread_exit(0);
}

int main(int argc, char *argv[])
{
        int i;
        pthread_t tid[THREAD_NUM]; /* the thread identifier */
        pthread_attr_t attr; /* set of attributes for the thread */

        if (argc != 2) {
                fprintf(stderr,"usage: a.out <integer value>\n");
                return -1;
        }

        if (atoi(argv[1]) < 0) {
                fprintf(stderr,"Argument %d must be non-negative\n",atoi(argv[1]));
                return -1;
        }

        /* get the default attributes */
        pthread_attr_init(&attr);

        /* create the thread */
        for (i=0;i<THREAD_NUM;i++)
                pthread_create(&tid[i],&attr,runner,argv[1]);

        /* now wait for the thread to exit */
        for (i=0;i<THREAD_NUM;i++)
                pthread_join(tid[i],NULL);

        printf("sum = %d\n",sum);
}

Answer 1

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

/* Function prototypes for thread routines */
void *sub_a(void *);
void *sub_b(void *);
void *sub_c(void *);
void *sub_d(void *);
void *sub_e(void *);
void *sub_f(void *);

thread_t thr_a, thr_b, thr_c;

void main()
{
thread_t main_thr;

main_thr = thr_self();
printf("Main thread = %d\n", main_thr); 

if (thr_create(NULL, 0, sub_b, NULL, THR_SUSPENDED|THR_NEW_LWP, &thr_b))
        fprintf(stderr,"Can't create thr_b\n"), exit(1);

if (thr_create(NULL, 0, sub_a, (void *)thr_b, THR_NEW_LWP, &thr_a))
        fprintf(stderr,"Can't create thr_a\n"), exit(1);

if (thr_create(NULL, 0, sub_c, (void *)main_thr, THR_NEW_LWP, &thr_c))
        fprintf(stderr,"Can't create thr_c\n"), exit(1);

printf("Main Created threads A:%d B:%d C:%d\n", thr_a, thr_b, thr_c); 
printf("Main Thread exiting...\n"); 
thr_exit((void *)main_thr);
}

void *sub_a(void *arg)
{
thread_t thr_b = (thread_t) arg;
thread_t thr_d;
int i;

printf("A: In thread A...\n"); 

if (thr_create(NULL, 0, sub_d, (void *)thr_b, THR_NEW_LWP, &thr_d))
        fprintf(stderr, "Can't create thr_d\n"), exit(1);

printf("A: Created thread D:%d\n", thr_d); 

/* process 
*/
for (i=0;i<1000000*(int)thr_self();i++);
printf("A: Thread exiting...\n"); 
thr_exit((void *)77);
}

void * sub_b(void *arg)
{
int i;

printf("B: In thread B...\n"); 

/* process 
*/

for (i=0;i<1000000*(int)thr_self();i++);
printf("B: Thread exiting...\n"); 
thr_exit((void *)66);
}

void * sub_c(void *arg)
{
void *status;
int i;
thread_t main_thr, ret_thr;

main_thr = (thread_t)arg;

printf("C: In thread C...\n"); 

if (thr_create(NULL, 0, sub_f, (void *)0, THR_BOUND|THR_DAEMON, NULL))
        fprintf(stderr, "Can't create thr_f\n"), exit(1);

printf("C: Join main thread\n"); 

if (thr_join(main_thr,(thread_t *)&ret_thr, &status)) 
        fprintf(stderr, "thr_join Error\n"), exit(1);

printf("C: Main thread (%d) returned thread (%d) w/status %d\n", main_thr, ret_thr, (int) status); 

/* process 
*/

for (i=0;i<1000000*(int)thr_self();i++);
printf("C: Thread exiting...\n"); 
thr_exit((void *)88);
}


void * sub_d(void *arg)
{
thread_t thr_b = (thread_t) arg;
int i;
thread_t thr_e, ret_thr;
void *status;

printf("D: In thread D...\n"); 

if (thr_create(NULL, 0, sub_e, NULL, THR_NEW_LWP, &thr_e))
        fprintf(stderr,"Can't create thr_e\n"), exit(1);

printf("D: Created thread E:%d\n", thr_e); 
printf("D: Continue B thread = %d\n", thr_b); 

thr_continue(thr_b);
printf("D: Join E thread\n"); 

if(thr_join(thr_e,(thread_t *)&ret_thr, &status)) 
        fprintf(stderr,"thr_join Error\n"), exit(1);

printf("D: E thread (%d) returned thread (%d) w/status %d\n", thr_e, 
ret_thr, (int) status); 

/* process 
*/

for (i=0;i<1000000*(int)thr_self();i++);
printf("D: Thread exiting...\n"); 
thr_exit((void *)55);
}


void * sub_e(void *arg)
{
int i;
thread_t ret_thr;
void *status;

printf("E: In thread E...\n"); 
printf("E: Join A thread\n"); 

if(thr_join(thr_a,(thread_t *)&ret_thr, &status)) 
        fprintf(stderr,"thr_join Error\n"), exit(1);

printf("E: A thread (%d) returned thread (%d) w/status %d\n", ret_thr, ret_thr, (int) status); 
printf("E: Join B thread\n"); 

if(thr_join(thr_b,(thread_t *)&ret_thr, &status)) 
        fprintf(stderr,"thr_join Error\n"), exit(1);

printf("E: B thread (%d) returned thread (%d) w/status %d\n", thr_b, ret_thr, (int) status); 
printf("E: Join C thread\n"); 

if(thr_join(thr_c,(thread_t *)&ret_thr, &status)) 
        fprintf(stderr,"thr_join Error\n"), exit(1);

printf("E: C thread (%d) returned thread (%d) w/status %d\n", thr_c, ret_thr, (int) status); 

for (i=0;i<1000000*(int)thr_self();i++);

printf("E: Thread exiting...\n"); 
thr_exit((void *)44);
}


void *sub_f(void *arg)
{
int i;

printf("F: In thread F...\n"); 

while (1) {
        for (i=0;i<10000000;i++);
        printf("F: Thread F is still running...\n"); 
        }
}