multithreading - Why this python multi-thread approach take more time than single thread to solve the same task? -

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why python multi-thread approach take more time single thread solve same problem?

note computer multi-core processor cpu.

i wrote same code in both ways , make comparison. surprisingly single thread way faster! have thoughts?

#!/usr/bin/python  l = [1,2,3,4,5,7,8,9,10]  def gen(index,value):     if index==len(l):         return 1     count=0     in range(len(value)+1):         count+=gen(index+1,value[:i]+[l[index]]+value[i:])     return count   #single thread approach print gen(1,[1]) #this takes 480ms run!    #multi-thread approach threading import thread def t1_start():     global pointer1     pointer1=gen(2,[2,1])  def t2_start():     global pointer2     pointer1=gen(2,[1,2])  pointer1=0 pointer2=0 t1=thread(target=t1_start,args=()) t2=thread(target=t2_start,args=()) t1.start() t2.start() t1.join() t2.join() #print pointer1+pointer2 #this takes 650ms run!

i've had problem in java. users suggested overhead, creation of threads costs, slowing down much, took longer. recommend try threaded code really complex calculations , more numbers in gen(index, value) function. threaded code might better simple solution, if gen function take more time.


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