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

[Michael Van Canneyt]

On Wed, 20 Oct 2010, Alexander Klenin wrote:

> On Wed, Oct 20, 2010 at 05:36, Michael Van Canneyt
> <michael at freepascal.org> wrote:
>> On Wed, 20 Oct 2010, Alexander Klenin wrote:
>>> On Wed, Oct 20, 2010 at 01:45, Michael Van Canneyt
>>> <michael at freepascal.org> wrote:
>>>> Try and improve that class with ansistrings. If you succeed, only then we
>>>> can start making a case for using them in the compiler.
>>>
>>> Ok, I went ahead and have taken look at the code.
>>> I assume you speak about TFPHashList vs TFPCustomHashTable.
>>> The classes are not really comparable, because they use quite
>>> different internal data structures.
>>
>> But they perform the same function; hash on string with an
>> associated data structure.
>
> Sure, but in a very different manner.
> Look at the code yourself if you do not believe me ;-)

I know it quite well. 
But both classes serve approximately the same functional purpose: a hash.

>>> Benchmarking included 3*10^6 calls to Add and Find methods
>>> with the arguments of various lengths.
>>>
>>> Average string length 5 characters:
>>> ShortString: 1.15 s
>>> AnsiString: 1.56 s
>>>
>>> Average string length 45 characters:
>>> ShortString: 12.0 s
>>> AnsiString: 3.2 s
>>>
>>> I agree that the first case is more relevant for the compiler,
>>> but still you can see that ShortStrings are clearly not always faster.
>>
>> I'm always open for benchmark tests.
>>
>> Can you please send me your test and the implementation ?
>> I'd like to see when the balance shifts.
>
> Sure, see attachment.
> Note that I made shortstring->ansistring text replacament
> followed by minimal fixed to get working Add and Find methods.
> Other methods may be broken as a result.

At the moment, it's just for benchmarking.

Thank you for the code.

Michael.