Using pthread in c++ to find max of array

Question

;I am trying to use the pthread.h library to find the minimum number from an array. I am having trouble getting the code to compile and am unfamiliar with how to use pointers properly to make it work.

#include <iostream>
#include <pthread.h>
using namespace std;

int *min;
int *max;
double *average;
int n;

void* minimum(void* a){
  int size = n;
  int* array = (int*) a;
  int tempmin = array[0];
  for(int i=0; i<size; i++){
    if(array[i] < tempmin){
      tempmin = array[i];
    }
  }
  return NULL;
}

int main(){

int in;

cout << "How many numbers would you like to enter?" << endl;
cin >> n;
int numbers[n];
  for(int i=0; i<n; i++){
      cout << "enter number " << i+1 << endl;
      cin >> in;
      numbers[i] = in;
    }

pthread_t thread1;
int iret1

pthread_create(&thread1, NULL, &minimum, (void*)numbers);
}

Answer 1

I am assuming this is just an exercise, since there are better ways to achieve what you want. Please read this link . So here are some points to watch for:

1 - After pthread_create, you should call pthread_join to wait for it to complete and also to release its resources (you could also create a detached thread). You also need to pass the array to the thread as an argument:

pthread_create(&thread1, NULL, &minimum, (void*)numbers);
pthread_join(thread1, NULL);

2 - The thread function receives a void*, so you need to cast it to whatever the argument really is:

void* minimum(void* a){
  int size = n;
  int* array = (int*) a;
  int tempmin = array[0];
  for(int i=0; i<size; i++){
    if(array[i] < tempmin){
      tempmin = array[i];
    }
  }
  return NULL;
}