Proper parallel version of Raspberry Pi cluster code from https://www.the-diy-life.com/can-my-water-cooled-raspberry-pi-cluster-beat-my-macbook/

primes-parallel.py

# Requires pip install unsync
import time
from unsync import unsync
import multiprocessing as mp
import sys

#Start and end numbers
start_number = 1
num_processes = mp.cpu_count()


def chunks(seq, chunks):
        size = len(seq)
        start = 0
        for i in range(1, chunks + 1):
            stop = i * size // chunks
            yield seq[start:stop]
            start = stop


@unsync(cpu_bound=True)
def find_in_range(seq):
    noPrimes = 0
    #Loop through each number, then through the factors to identify prime numbers
    primes = []
    for candidate_number in seq:
        found_prime = True
        for div_number in range(2, candidate_number):
            if candidate_number % div_number == 0:
                found_prime = False
                break
        if found_prime:
            primes.append(candidate_number)
            noPrimes += 1

    return primes

def run():
    #Create variable to store the pr
    # ime numbers and a counter
    primes = []

    ranges = chunks(list(range(2, upper_bound)), num_processes)
    # for l in ranges:
    #     print(list(l))
    # print(len(list(ranges)))

    #Record the test start time
    start = time.time()

    tasks = []
    for r in ranges:
        tasks.append(find_in_range(r))

    for t in tasks:
        # print(t.result())
        primes.extend(t.result())

    
    #Once all numbers have been searched, stop the timer
    end = round(time.time() - start, 2)

    #Display the results, uncomment the last to list the prime numbers found
    print('Find all primes up to: ' + str(upper_bound))
    print('Time elasped: ' + str(end) + ' seconds')
    print('Number of primes found ' + str(len(primes)))
    #print(primes)
   
if __name__ == "__main__":
    upper_bound = int(input("Number of primes: "))
    print(f"Using {num_processes} cores.")

    run()