Author: Daniel Shawul
Date: 06:25:44 11/17/03
Go up one level in this thread
On November 17, 2003 at 08:25:09, Tord Romstad wrote:
>On November 17, 2003 at 07:30:59, Daniel Shawul wrote:
>
>>you are right,i meant deeper? Do you know any good place sir?
>>i have found rebel's programming
>>topics(http://members.home.nl/matador/chess840.htm) but you know
>>they evaluate each node of the tree,which is quite costy for my program.
>
>Without evaluating interior nodes, how are you going to do any static
>forward pruning or reductions at all?
ofcourse I evaluate the nodes I want to razor.But rebel evaluates
"all" the nodes to do further reductions.The programmer of rebel suggests
drastic changes have to be made to use his reduction methods.
>
>>Also I tried to reduce the search depth by 1, if score + margin < alpha
>>for depths greater than 3.
>
>Techniques like this seem to be very common (even in strong programs like
>Rebel), but I am becoming more and more convinced that they are
>fundamentally unsound. The problem is that you may encounter the same
>position somewhere else in the search tree where the value of alpha is
>different. When you look up the old search results in the hash table,
>you get a search inconsistency.
>
I totally agree with you!
>IMHO, it is a sounder idea to base forward pruning, extension and reduction
>decisions on how each move affects the different components of the evaluation
>function. As an example, you could consider the following idea:
>
>In a position where one of the pieces for the side to move is hanging,
>reduce all moves which satisfies all of the following criterions:
>
>1. The move is not a capture.
>2. The move is not a check.
>3. The move does not defend the hanging piece, nor bring the hanging
> piece into safety.
>4. The move does not threaten any of the enemy pieces.
>5. The move does not increase the pressure on the opponent's king.
>6. The move does not increase the passed pawn evaluation (for instance
> by advancing a passed pawn, or by supporting an unblocked advanced
> passed pawn by a rook or a king).
>
>Tord
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