Python Threading Performance vs. Number of cores [duplicate]

Question

I am new to python and I am learning threading and GIL. These are the stats oflscpu command :

 Architecture:          x86_64
 CPU op-mode(s):        32-bit, 64-bit
 Byte Order:            Little Endian
 CPU(s):                4
 On-line CPU(s) list:   0-3
 Thread(s) per core:    2
 Core(s) per socket:    2
 Socket(s):             1
 NUMA node(s):          1
 Vendor ID:             GenuineIntel
 CPU family:            6
 Model:                 69
 Stepping:              1
 CPU MHz:               1700.062
 BogoMIPS:              4789.05
 Virtualization:        VT-x
 L1d cache:             32K
 L1i cache:             32K
 L2 cache:              256K
 L3 cache:              3072K
 NUMA node0 CPU(s):     0-3

When I ran this simple python threading example, I get the following output.

import time
import threading

def counter(n):
    for i in range(0,n):
        i = i+1
    return

t1 = threading.Thread(target=counter, args = (10000000,))
t2 = threading.Thread(target=counter, args = (10000000,))

t0 = time.clock()
t1.start()
t2.start()
t1.join()
t2.join()
t3 = time.clock()

print "Total time : %s"%str(t3-t0)

bash@bash:~/Desktop$ python threads.py
Total time : 2.115326

But when I disable 3 cores and re-run the code :

bash@bash:~/Desktop$ python threads.py
Total time : 1.115442

These figures remain more or less the same. Why is this so?? Someone explain. Thanks in advance...

Answer 1

The threading library you are using does not actually utilize multiple cores simultaneously for computation.

Try using the multiprocessing module instead for computational threading, you should see more "expected" results.