Results are not matching in Chapter 1 example 2

[UsNizami]

In example 2 of chapter 1. When I run the file I get

Result is very large. Only printing the last 5 digits: 35443
Sequential took: 0.05 seconds.
Result is very large. Only printing the last 5 digits: 45807
Concurrent took: 0.02 seconds.

but 35433 is not equal to 45807. The results should be equal to 35443. What is the issue here ?

[Matej-Chmel]

The lack of synchronization in the script enables the interpreter to switch threads in the middle of the computation of the f function. This race condition sometimes makes the script to report the wrong result.

You can solve this issue by applying a lock:

import threading

def concurrent_f(x):
    global result
    with lock:
    	result = f(result)

lock = threading.Lock()

Or by increasing the switch interval at the beginning of the script:

import sys
sys.setswitchinterval(1) # The default is 0.005 (5 ms)

This is not ideal solution but it doesn't modify the original concurrent_f function.