On 12/17/2015 04:18 PM, Robert Hanson wrote:
> On Thu, Dec 17, 2015 at 8:30 AM, Rolf Huehne <rhue...@leibniz-fli.de> wrote:
>
>> On 12/17/2015 04:39 AM, Robert Hanson wrote:
>>> Wow, what a GREAT FIND, Eric! Say you have a set of information in the
>> form
>>> of an array for n items. Now you need to set the value for n+1. Well, of
>>> course you were efficient in your creating an array of just n values, so
>>> now you have to create a NEW array that is n+1 long instead of n long.
>>> That's pretty fast, if you do it once. But now do this:
>>>
>>> a = [];
>>> for (i = 0; i < 20000; i++) {
>>> if (a.length < i + 1)
>>> a = copyArray(a, i + 1);
>>> }
>>>
>>> See the problem? Not only are you creating an array that is 20000 long,
>> you
>>> are creating a new array from an old one *20000 times. *Ouch!
>>>
>> Bob, I also tried to avoid this in Jmol scripting by setting the last
>> value of an array first:
>>
>> var parsedData = [];
>> parsedData[tsvData.size] = 0;
>>
>> Would you confirm that this will actually work?
>>
>>
> When I tried this:
>
> t = now()
> a = []
> a[20000] = 0
> for (i = 1; i < 20000; i++) a.push(i)
> print now(t)
>
> t = now()
> a = []
> for (i = 1; i < 20000; i++) a.push(i)
> print now(t)
>
> I found the first was about 5% faster than the second in both Java and
> HTML5. You could experiment yourself with that.
>
I got mixed results:
In Java the first one was much slower than the second one (210,142) in
the first run. In subsequent runs the times were more similar (72,71;
69,75; 69,70; 69,70).
In HTML5 the second one was always slightly faster (3277,3177;
3248,3136; 3164,3146; 3632,3543; 3565,3419).
Regards,
Rolf
--
Rolf Huehne
Postdoc
Leibniz Institute on Aging - Fritz Lipmann Institute (FLI)
Beutenbergstrasse 11
07745 Jena, Germany
Phone: +49 3641 65 6205
Fax: +49 3641 65 6210
E-Mail: rhue...@leibniz-fli.de
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