create thread - passing arguments

Question

I am attempting on creating multiple threads that each thread calculates a prime. I am trying to pass a second argument to a function using thread create. It keeps throwing up e

Answer 1

In case of std::thread, the user can pass arguments to the thread function in the following method

std::thread(funcName,arg1,arg2);

for instance,

//for a thread function, 
void threadFunction(int x,int y){
   std::cout << x << y << std::endl;
}

// u can pass x and y values as below
std::thread mTimerThread;
mTimerThread = std::thread(threadFunction,1,12);

Answer 2

You can only pass a single argument to the function that you are calling in the new thread. Create a struct to hold both of the values and send the address of the struct.

#include <pthread.h>
#include <stdlib.h>
typedef struct {
    //Or whatever information that you need
    int *max_prime;
    int *ith_prime;
} compute_prime_struct;

void *compute_prime (void *args) {
    compute_prime_struct *actual_args = args;
    //...
    free(actual_args);
    return 0;
}
#define num_threads 10
int main() {
    int max_prime = 0;
    int primeArray[num_threads];
    pthread_t primes[num_threads];
    for (int i = 0; i < num_threads; ++i) {
        compute_prime_struct *args = malloc(sizeof *args);
        args->max_prime = &max_prime;
        args->ith_prime = &primeArray[i];
        if(pthread_create(&primes[i], NULL, compute_prime, args)) {
            free(args);
            //goto error_handler;
        }
    }
    return 0;
}

Answer 3

This is the code of Manakarse , everything is really good but you need a

pthread_join(thread[i],NULL)

just to be sure all of threads will successfully execute before end of main thread("main will "waiting" while all of threads aren't finished yet) ;