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Subject: Re: Improvements in BF makes my MoveGen suck =(

Author: Sune Fischer

Date: 08:13:37 06/27/03

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On June 27, 2003 at 11:00:56, Uri Blass wrote:

>On June 27, 2003 at 10:46:08, Sune Fischer wrote:
>
>>On June 27, 2003 at 08:13:53, Albert Bertilsson wrote:
>>
>>>Just wanted to share my latest findings and warn you from making the same
>>>mistake (or maybe I just point out the obvious).
>>>
>>>I've always been proud to have a very fast movegen, doing perft calculations
>>>very fast. I optimized the movegen alot, and always saw playing strength
>>>increasing. I use a legal move generator and always saw the cost of verifying
>>>legality to be minor. Lately however I've noticed that the engine performance
>>>isn't that great (compared to other engines) inspite of the fast movegen. So I
>>>started digging today and the numbers struck me as lightning...
>>>
>>>As I've improved moveordering very much with hashtable/iterative deepening,
>>>killer moves and history tables the effective BF is now much lower. The lower BF
>>>now means that very few moves of all the generated ones are actually ever made.
>>>This means that the cost of generating legal moves have increased incredibly
>>>much.
>>>
>>>It's really anoying to notice that something you though was very good now is on
>>>the list of improvements again =(.
>>>
>>>/Regards Albert
>>
>>What that saying with premature optimization being the root of all evil? :)
>>
>>Well it think it is correct, and probably a typical mistake to spend oceans of
>>time optimizing one thing only.
>
>I do not think that the Albert spent ocean of time in optimizing.
>Based on reading his posts I got the impression that he did not do it.

Ah hmm, but I get the opposite impression. :)

>His program is relatively fast in perft because his program has a different
>structure(he use legal move generator when most of the programmers do not do
>it).

Perft is no good speed indicator anyway, not even for a move gen.
The perft tree is so different from the chess tree.

Optimizing for perft is basicly like building a formula 1 car to use for
off-road rally.

-S.
>Uri



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