Author: Tony Werten
Date: 09:42:52 06/25/02
Go up one level in this thread
On June 25, 2002 at 09:15:35, Georg v. Zimmermann wrote:
>Hi,
>
>yesterday tried to implement an idea I saw in Crafty about not trying a nullmove
>if hash table tells us it will probably not work:
>
> // NullMove : passing should be worse than any other move.
>
> if ((NULL_REDUCTION)
>
> // no null move if hash tells us position is bad
>
> ( (te->depth < alphadepth - NULL_REDUCTION * ONE_PLY)
> || (te->type == FAIL_HIGH)
> || (te->value >= beta) )
>
> && (AIBoard.nullCondition(alphadepth)) )
> {
> // NullMoveAlgo [...]
> }
>
>This avoids thousands of useless null move tries in my tests. While when I let
>it spit out positions where this would have prevented a successfull null move
>try I only got 4 in 60 mill. nodes.
>
>Regardless it didnt reduce overall node-count in my tests by more than 1% !
>What can be the reasons for that ?
>Maybe the 4 positions where the idea fails are a big factor because they take
>almost as long to search than all the shallower null move searches ? Sounds
>unlikely.
>Maybe the shallower null move searches are needed as kind of "Internal null move
>deepening": when at a higher depth suddenly the hash tells me not to not try
>null move anymore I dont have info from shallower null moves in the TT ?
>
>Any ideas how to test those assumptions ?
>
>
>Regards,
>
>Georg v. Zimmermann
Avoiding theses nullmoves kills your threat extensions.
Tony
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