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

Author: Uri Blass

Date: 08:31:30 06/27/03

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On June 27, 2003 at 11:13:37, Sune Fischer wrote:

>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. :)

I remember that in the winboard forum he said that he did not work much about
it.

He did not add a lot of tables to do his makemove slower and to do his gen
faster.

I believe that it can help me to do my perft faster but the main advantage is
the knowledge that I get from the tables and not speed.

>
>>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.

I think that it is dependent on the structure of the program.

Uri



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