Speed optimisation

Alex Tweedly alex at tweedly.net
Thu Oct 6 07:07:55 EDT 2005


Kay C Lan wrote:

> I certainly have to agee with Alex's statement about sitting back and
>
>watching. So here is my effort:
>
>  
>
>_______________________________________________
>
> So do I win the Cupie doll? ;-)

No, I don't think so, because your method gets wrong (IMHO) results in 
two cases :-).

1.  10:30:28 + 50 results in
Alex   10:31:18.0
Kay    10:31:18.
(i.e. trailing full stop (period) rather than a "0" after it)

2. 23:59:59.3 + 50 results in
Alex 24:00:49.4
Kay  00:00:49.4
and the original problem statement said  "hh can be greater than 24!" 
which I take to mean that it should be in cases like this, to avoid 
problems of knowing whether or not the values have wrapped. Using the 
built in time functions will always wrap, so that may require the 
surrounding code to change.

>I've got the same amount of lines as Sarah's but more words; but less word's
>than Alex's, assuming you set the twelveHourTime in an openStack handler.
>
>for 150000 calculations on my machine (run 3 consecutive times)
>
>IF the original time has no decimal ie 10:30:28
>Dick 5.78, 5.83, 5.86
>Alex 5.38, 5.73, 5.45
>me 5.48, 5.46, 5.55
>
>With decimal times ie 11:23:34.6
>Dick 6.05, 6.21, 6.13
>Alex 5.55, 5.65, 5.68
>me 5.4, 5.46, 5.58
>
>Dick's and Alex's seem to prefer no decimal, but mine doesn't seem fussed
>either way.
>
>  
>
Interesting. You didn't say what your machine was, but I get quite 
different results (Sony laptop, Pentium 4, WinXP), with my method 
consistently being faster then yours (note I set the twlevehourtime 
*outside* the timing loop).

(You didn't say what number of seconds you were adding, so I couldn't 
reproduce the comparison exactly. Note it does make a difference to some 
methods whether or not you need to carry the increment - though probably 
not to either of these two methods)

12:11:12.2 + 50
----------------
Alex   2.636 2.687 2.682
Kay    3.158 2.828 2.801

10:31:18 + 50
-------------
Alex  2.332 2.307 2.227
Kay   2.888 2.879 2.888

11:23:34.6 + 50
---------------
Alex 2.415 2.438 2.471
Kay  2.707 2.704 2.731

I think all this proves is:
1. we're down to the point where differences are tiny
2. hardware and OS may give different results
3. it's easy to get obsessive about speed beyond the point where it matters - I do it all the time !!


-- 
Alex Tweedly       http://www.tweedly.net



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