Python Multiprocessing module did not work properly - python-3.x

Question

I'm writing right now on a code which counts all Primenumbers up to the highest integer. The problem is that it would take way too long (about 35 days). So the solution was in our opinion the multiprocessing module, to count all Primenumbers in 4 seperated threads (process 1: starts with 1 steps +8, process 2: starts with 3 steps +8, process 3: starts with 5 steps +8, process 4: starts with 7 steps +8). That would test every odd number if it is a Primenumber.
But the following code don't work and we cant find the Problem.
Maybe one of you can help me?
from multiprocessing import Process
import time
import math
timeStart = 0
timeEnd = 0
def istTeilbar (x, y):
if x%y == 0:
return True
return False
def istPrimzahl (x):
for i in range(2, int(math.sqrt(x))+1):
if istTeilbar(x, i):
return False
return True
def schreibePrimzahlBis1 (x):
counter1 = 0
print ("x")
for i in range(1, x, 8):
if istPrimzahl(i):
counter1 = counter1 +1
print (f'Das waren {counter1} Primzahlen\n')
def schreibePrimzahlBis2 (x):
counter2 = 0
for i in range(3, x, 8):
if istPrimzahl(i):
counter2 = counter2 +1
print (f'Das waren {counter2} Primzahlen\n')
def schreibePrimzahlBis3 (x):
counter3 = 0
for i in range(5, x, 8):
if istPrimzahl(i):
counter3 = counter3 +1
print (f'Das waren {counter3} Primzahlen\n')
def schreibePrimzahlBis4 (x):
counter4 = 0
print ('counter4')
for i in range(7, x, 8):
if istPrimzahl(i):
counter4 = counter4 +1
print (f'Das waren {counter4} Primzahlen\n')
grenze = input("Die letzte zu testende Zahl:\n")
timeStart = time.time()
p1 = Process(target=schreibePrimzahlBis1, args=[int(grenze)])
p2 = Process(target=schreibePrimzahlBis2, args=[int(grenze)])
p3 = Process(target=schreibePrimzahlBis3, args=[int(grenze)])
p4 = Process(target=schreibePrimzahlBis4, args=[int(grenze)])
p1.start()
p2.start()
p3.start()
p4.start()
p1.join()
p2.join()
p3.join()
p4.join()
timeEnd = time.time()
print (f'Das hat ca. {timeEnd-timeStart} sekunden gedauert.')
The original code which would take way to long if you are intersted in:
import time
import math
timeStart = 0
timeEnd = 0
def istTeilbar (x, y):
if x%y == 0:
return True
return False
def istPrimzahl (x):
for i in range(2, int(math.sqrt(x))+1):
if istTeilbar(x, i):
return False
return True
def schreibePrimzahlBis (x):
counter = 0
for i in range(2, x):
if istPrimzahl(i):
if counter == 10000:
print (10000)
elif counter == 100000:
print (100000)
elif counter == 1000000:
print (1000000)
elif counter == 10000000:
print (10000000)
elif counter == 100000000:
print (100000000)
counter = counter +1
print ('Das waren')
print (counter)
print ('Primzahlen.\n')
grenze = input("Die letzte zu testende Zahl:\n")
timeStart = time.time()
schreibePrimzahlBis(int(grenze))
timeEnd = time.time()
print ('Das hat ca.')
print (timeEnd-timeStart)
print ('sekunden gedauert')
´´´

Answer 1

One way to parallelize tasks is to use concurrent.futures. I personally like this solution. Maybe you want to try this :
import concurrent.futures
function_A(arg1, arg2):
...
return val_A
function_B(arg1, arg2, arg3):
...
return val_B
if __name__ == '__main__':
arg1, arg2, arg3 = ...
with concurrent.futures.ThreadPoolExecutor() as executor:
future_A = executor.submit(function_A, arg1, arg2)
future_B = executor.submit(function_B, arg1, arg2, arg3)
print(future_A.result())
print(future_B.result())