[fpc-devel] TFPHashList (Was: Alternative parsers)

[Alexander Klenin]

On Thu, Oct 21, 2010 at 00:03, Sergei Gorelkin <sergei_gorelkin at mail.ru> wrote:
> Alexander Klenin пишет:
> Running the test, I get quite opposite results:
>
> 0.750 sec
> 0.766 sec
> short add:  1.829 sec
> short find: 0.781 sec
> ansi add:   1.750 sec
> ansi find:  1.406 sec
>
> The only modifications I made to the test is added printing separate numbers
> for 'find' and 'add', and printing labels. Modified test is attached.

What CPU? I have Core i3 540.

> Although theoretically Find() should show no difference at all, because it
> performs the same operations on the same data. IOW, the difference seen is
> caused either by CPU cache effects, or by bugs in testing.

I suspect that the main culprit may be the relatively slow
implementation of built-in AnsiString operator=.
ShortString code contains a strange construct in InternalFind function,
clearly designed to bypass built-in operator=.
I removed that construct during ansistring conversion.

> No difference between the first two numbers (IntToStr for ShortString and
> AnsiString) is also quite suspicious...

This is probably because the time is dominated by the conversion itself.
IOW, IntToStr is so slow that string type does not matter in comparison.

-- 
Alexander S. Klenin