Author: Omid David Tabibi
Date: 19:22:33 10/04/03
Go up one level in this thread
On October 04, 2003 at 18:57:18, Vincent Diepeveen wrote:
>On October 04, 2003 at 18:40:08, Russell Reagan wrote:
>
>Just put next in your engine:
> - checks in qsearch at the first ply (or when you already did them
> just stick to what you did now; in diep i do them at any ply in qsearch
> btw, but most have problems controlling that so i do not mind it if you
> just try 1 ply)
> - nullmove search with window alfa,beta = -mate+1000,
> so you'll find 100% sure a mate threat
>
> - if you see a mate threat you extend that position by 1 ply and store
> in hashtable this position got a mate extension.
>
> - now you extend moves double sometimes. So recapture that gives extension,
> you extend. If the same move also gives opponent a check, another extension.
> So you can extend 2 plies then.
2 plies extension at once? What if you detected a mate threat and played a move
which is a recapture and also checks the opponent? Extend by 3 plies?!
Seems a little frightening! But will try it tonight...
Looking at Fritz's parameters, the default values are selectivity=2, and
futility pruning activated. So, we can assume that Fritz is using R=2. However,
looking at its analysis it rapidly reaches very deep while not ignoring any
significant tactical threats. That's also the case with Shredder, which uses
selectivity=-1 (it is not a typo, -1 ?!) and futility=2.
Falcon's tactical strength is somewhat superior to that of Crafty, but comparing
it to other null-movers, Fritz and Shredder, it is way behind in tactics...
BTW, when in quiescence you detect that one side is in check, do you do the
following:
int quiesce(int alpha, int beta) {
...
if (checked)
return search(alpha, beta, 1);
...
}
I haven't implemented checks in quiescence yet, but it seems inevitable...
>>I don't think Christophe uses null move. At least, if he does, I don't think
>>it's the "main algorithm" contributing to Chess Tiger's strength. I remember
>
>May i beg your pardon?
>
>Without nullmove you can go home.
Junior and Rebel are good examples of non null-mover successful programs. And
there are some strange programs like Hiarcs; I don't think it is using null-move
pruning, at least not anything with R > 1.
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