python multi-threading slower than serial?

Question

I\'m trying to figure out multi-threading programming in python. Here\'s the simple task with which I want to compare serial and parallel speeds.

import thr         


        

Answer 1

Python libraries that are written in C can obtain/release the Global Interpreter Lock (GIL) at will. Those that do not use Python objects can release the GIL so that other threads can get a look-in, however I believe that the math library uses Python Objects all the time, so effectively math.sin is serialised. Since locking/unlocking is an overhead, it is not unusual for Python threads to be slower than processes.