Code with random module faster on the vm than the vm host...

Mark Lawrence breamoreboy at yahoo.co.uk
Mon Nov 11 02:31:46 CET 2013


On 11/11/2013 01:15, Ned Batchelder wrote:
> On Friday, November 8, 2013 12:48:04 PM UTC-5, Pascal Bit wrote:
>> Here's the code:
>>
>> from random import random
>> from time import clock
>>
>> s = clock()
>>
>> for i in (1, 2, 3, 6, 8):
>>       M = 0
>>       N = 10**i
>>
>>       for n in xrange(N):
>>           r = random()
>>           if 0.5 < r < 0.6:
>>               M += 1
>>
>>       k = (N, float(M)/N)
>>
>> print (clock()-s)
>>
>> Running on win7 python 2.7 32 bit it uses around 30 seconds avg.
>> Running on xubuntu, 32 bit, on vmware on windows 7: 20 seconds!
>> The code runs faster on vm, than the computer itself...
>> The python version in this case is 1.5 times faster...
>> I don't understand.
>>
>> What causes this?
>
> The docs for time.clock() make clear that the meaning on Windows and Unix are different:
>
> "On Unix, return the current processor time as a floating point number expressed in seconds."
>
> "On Windows, this function returns wall-clock seconds elapsed since the first call to this function..."
>
> Try the experiment again with time.time() instead.
>
> --Ned.
>

http://www.python.org/dev/peps/pep-0418/ for some related reading about 
Python time functions.

-- 
Python is the second best programming language in the world.
But the best has yet to be invented.  Christian Tismer

Mark Lawrence




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