Linear Search Using Multi-Threading in C

Here we will see how to apply the multi-threading concept to search one element in an array. Here the approach is very simple. We will create some threads, then divide the array into different parts. Different thread will search in different parts. After that, when the element is found, enable the flag to identify this.

Example

#include <stdio.h>
#include <pthread.h>
#define MAX 16
#define THREAD_MAX 4
int array[MAX] = { 1, 5, 7, 10, 12, 14, 15, 18, 20, 22, 25, 27, 30, 64, 110, 220 };
int key = 18;
int flag = 0; //flag to indicate that item is found in the array or not
int current_thread = 0;
void* ThreadSearch(void* args) { //This is linear search function. It will be running using all threads
   int num = current_thread++;
   for (int i = num * (MAX / 4); i < ((num + 1) * (MAX / 4)); i++){
      if (array[i] == key)
         flag = 1; //set flag if key is found
   }
}
int main() {
   pthread_t thread[THREAD_MAX];
   for (int i = 0; i < THREAD_MAX; i++) { //create multiple threads
      pthread_create(&thread[i], NULL, ThreadSearch, (void*)NULL);
   }
   for (int i = 0; i < THREAD_MAX; i++) {
      pthread_join(thread[i], NULL); //wait untill all of the threads are completed
   }
   if (flag == 1)
      printf("Key element is found
");
   else
      printf("Key element is not present
");
}

Output

$ gcc 1249.Thread_search.cpp -lpthread
$ ./a.out
Key element is found