Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.python > #64667 > unrolled thread

Re: generate De Bruijn sequence memory and string vs lists

Back to article view | Back to comp.lang.python

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: generate De Bruijn sequence memory and string vs lists Peter Otten <__peter__@web.de> - 2014-01-24 09:23 +0100

#64667 — Re: generate De Bruijn sequence memory and string vs lists

Vincent Davis wrote:

> Excellent Peter!
> I have a question, the times reported don't make sense to me, for example
> $ python3 -m timeit -s 'from debruijn_compat import debruijn_bytes as d'
> 'd(4, 8)'
> 100 loops, best of 3: 10.2 msec per loop
> This took ~4 secs (stop watch) which is much more that 10*.0102 Why is
> this?

Look at the output, it's "100 loops"

100 * 10 msec == 1 sec

together with "best of 3" you are already at 3 sec, minimum as it is the 
"best" run.

Then, how do you think Python /knows/ that it has to repeat the code 10 
times on my "slow" and 100 times on your "fast" machine? It runs the bench 
once, then 10, then 100, then 1000 times -- until there's a run that takes 
0.2 secs or more. The total expected minimum time without startup overhead 
is then

+----calibration------+   +-measurement--+
(1 + 10 + 100) * 10msec + 3 * 100 * 10msec

or about 4 secs.

> $ python3 -m timeit -s 'from debruijn_compat import debruijn_bytes as d'
> 'd(4, 11)'
> 10 loops, best of 3: 480 msec per loop​
> This took ~20 secs vs .480*10

>>> .480*(1 + 10 + 3*10)
19.68

> d(4, 14) takes about 24 seconds (one run)

This is left as an exercise ;)

[toc] | [standalone]

Back to top | Article view | comp.lang.python

csiph-web