Computer Chess Club Archives




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

Author: Tom Likens

Date: 08:34:43 06/27/03

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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
>It's really anoying to notice that something you though was very good now is on
>the list of improvements again =(.
>/Regards Albert

I'm not sure I see the problem.  Essentially, your engine is just as
fast as ever with the only difference being that you are eliminating
nonsensical lines of play that you used to search.  You're right this
will make your move generator do more work per move searched, but
it still seems like a win overall.  My guess is that the new version,
all things being equal, will more than likely outsearch and outplay
the old version (which is the real goal).

If you really want to "speed" things up, you could throw out *all*
move ordering, your nodes/sec will go through the roof ;)


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