corrected multi process version of the prime number counter from https://www.youtube.com/watch?v=hGyJTcdfR1E

search-for-primes.py

import multiprocessing as mp
import time
import pandas as pd


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


def calc_primes(numbers):
    num_primes = 0
    primes = []

    # Loop through each number, then through the factors to identify prime numbers
    for candidate_number in numbers:
        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)
            num_primes += 1
    return num_primes


def main(pnum=mp.cpu_count(), cnum=mp.cpu_count() * 16, maxNum=10000):
    # Record the test start time
    start = time.time()

    pool = mp.Pool(pnum)

    # 0 and 1 are not primes
    parts = chunks(range(2, maxNum, 1), cnum)
    # run the calculation
    results = pool.map(calc_primes, parts)
    total_primes = sum(results)

    pool.close()

    # 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
    profilingStats = {
        'primeNumbers': maxNum,
        'processCount': pnum,
        'chunkNumber': cnum,
        'time': end
    }
    return profilingStats


if __name__ == "__main__":
    stats = list()
    for m in [10, 100, 200, 500]:  # set your maximalSizes to iterate over
        for p in [1, 2, 4, 8]:  # set your numbers of processes per physical CPU thread here
            for c in [1, 2, 4]:  # set your chunk size per process here
                stats.append(main(p * mp.cpu_count(), p * c * mp.cpu_count(), m * 1000))
                print(stats[-1])

    data = pd.DataFrame.from_records(stats)
    data.to_csv("data.csv", index=False, header=False)