Binary search program written in C language, using pthread for multi-thread processing

#We know that the binary search method is the most suitable and effective sorting algorithm. This algorithm works on sorted sequences. The algorithm is simple, it just finds the element from the middle, then splits the list into two parts and moves to the left sublist or the right sublist.

We know its algorithm. Now we will see how to use the binary search technique in a multi-threaded environment. The number of threads depends on the number of cores present in the system. Let's take a look at the code to get the idea.

Example

#include <iostream>
#define MAX 16
#define MAX_THREAD 4
using namespace std;
//place arr, key and other variables as global to access from different thread
int arr[] = { 1, 6, 8, 11, 13, 14, 15, 19, 21, 23, 26, 28, 31, 65, 108, 220 };
int key = 31;
bool found = false;
int part = 0;
void* binary_search(void* arg) {
   // There are four threads, each will take 1/4th part of the list
   int thread_part = part++;
   int mid;
   int start = thread_part * (MAX / 4); //set start and end using the thread part
   int end = (thread_part + 1) * (MAX / 4);
   // search for the key until low < high
   // or key is found in any portion of array
   while (start < end && !found) { //if some other thread has got the element, it will stop
      mid = (end - start) / 2 + start;
      if (arr[mid] == key) {
         found = true;
         break;
      }
      else if (arr[mid] > key)
         end = mid - 1;
      else
         start = mid + 1;
   }
}
main() {
   pthread_t threads[MAX_THREAD];
   for (int i = 0; i < MAX_THREAD; i++)
      pthread_create(&threads[i], NULL, binary_search, (void*)NULL);
   for (int i = 0; i < MAX_THREAD; i++)
      pthread_join(threads[i], NULL); //wait, to join with the main thread
   if (found)
      cout << key << " found in array" << endl;
   else
      cout << key << " not found in array" << endl;
}

Output

31 found in array

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