program to check if numbers disprove the Collatz conjecture

collatz.py

import multiprocessing as mp

def worker(num):
    a = num
    b=0
    #if a becomes smaller than the number we are currently testing, then it is a previously tested number, and so we can discard the test.
    while a!=1 and a >= num:
        if a%2==0:
                a=(a/2)
        else:
                a=a*3+1
        #print(a)
        b+=1
    #print(str(num) + " failed in " + str(b) + " steps")


def main():
    #numbers up to 2^28, or about 2.95^20, have already been tested.
    start = 295000000000000000001
    #this could be replaced with any range, or an infinite loop.
    for i in range(1,100):
        #theoretically, larger batch sizes are more efficient, as the pool is recreated less often. Adjust as desired.
        stop = start + 100000000
        pool = mp.Pool(mp.cpu_count())
        pool.map(worker, range(start,stop,2))
        pool.close()
        print("numbers " + str(start) + " to " + str(stop) + " failed to disprove the collatz conjecture.")
        start = stop

if __name__ == "__main__":
  main()