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Multi-threaded Python Program for Linear Search

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Are you looking for an efficient way to search an element in Python?

The most common approach is to do Linear Search and when used in a multi-threaded fashion, it utilizes 100% of the CPU Core. In this article at OpenGenus, we demonstrate this by implementing Multi-threaded Linear Search in Python Programming.

In short, we divide the array into smaller chunks and then, each thread runs a separate chunk concurrently.

Table of contents:

  1. Linear Search using threads
  2. Python Implementation for Multi-threaded Linear Search

Linear Search using threads

  • Create a list of threads
threads = []
  • We create new threads and assign each thread a new chunk defined by start and end indices.
t = threading.Thread(target=linear_search, args=(arr, x, start, end))
  • We start and run the thread.
  • interrupt_main() is used to stop all threads when a particular thread finds the target element. This is an efficient way of terminating early. Other options would be to use a shared variable or a control variable/ flag which are not clean solutions.
  • Beyond it, we use threading.current_thread().result to store the result of each thread.
threading.current_thread().result = i
// ...
// If element is not found
threading.current_thread().result = -1
  • We wait for all threads to complete.
for t in threads:

Python Implementation for Multi-threaded Linear Search

Following is the complete Python program to do Linear Search in a multi-threaded way:

import threading

def parallel_linear_search(arr, x, num_threads):
    n = len(arr)
    chunk_size = n // num_threads

    threads = []

    # Create threads and search through different chunks of the array
    for i in range(num_threads):
        start = i * chunk_size
        end = n if i == num_threads - 1 else (i + 1) * chunk_size

        t = threading.Thread(target=linear_search, args=(arr, x, start, end))

    # Wait for all threads to finish and return the first index found
    for t in threads:

        if t.result != -1:
            return t.result

    # Element not found
    return -1

def linear_search(arr, x, start, end):
    for i in range(start, end):
        if arr[i] == x:
            threading.current_thread().result = i

    # Element not found in this chunk
    threading.current_thread().result = -1

if __name__ == '__main__':
    arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
    x = 7
    num_threads = 4

    idx = parallel_linear_search(arr, x, num_threads)

    if idx != -1:
        print(f"Element found at index {idx}")
        print("Element not found")

Save the above code in a file named LinearSearch.py and run it using the following command:

python LinearSearch.py

The output will be as follows:

Element found at index 6

With this article at OpenGenus, you must have the complete idea of how to implement Linear Search in a multi-threaded way in Python Programming Language.

Rahul Reddy

M.Tech in Computer Science and Engineering from IIT Bhubaneswar | SDE Intern at Flipkart

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