Author: Ralf Elvsén
Date: 14:54:50 07/21/00
Go up one level in this thread
On July 21, 2000 at 17:44:42, Georg v. Zimmermann wrote:
>On July 21, 2000 at 17:39:52, Eelco de Groot wrote:
>
>>I'm sure more than 10 people would be interested in idea number two if it had a
>>search function. What programming discussion were you looking for, exactly?
>>
>>Eelco
>
>Some explanation about Futility Pruning and lower bound by E.Heinz. I don't even
>know when it took place, someone pointed me to it.
>
>Georg :)
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(Beginning of old post)
Posted by Ernst A. Heinz on May 15, 2000 at 10:43:28:
In Reply to: Caution K v KBN and lazy eval or futility posted by Brian
Richardson on May 14, 2000 at 16:53:46:
Hi Brian,
>Tinker's q-search lazy eval (material - max_pos_score)> beta return (like
>standing pat?), and (material + queen+pawn) <= alpha return (quasi-futility?)
>was working fairly well, until a K vs KBN endgame. Since it was not getting to
>the eval function, the special mating code was never used and Tinker ended up
>with a 50 move draw...Now I check for opponent's pieces <= one minor and skip.
>
>This was discussed in ICCA Vol 21 # 2 (Extended Futility and Dark Thought). I
>also have tried various regular futility, extended futility and razoring (as
>outlined in the ICCA article), but they did not seem to help, at least given
>Tinker's mix of searching algorithims.
Most types of forward pruning which work well in the middlegame and
early endgame often backfire in situations with reduced material.
From my personal experience, the best remedies for this are:
1. less aggressive pruning in situations with reduced material,
2. more sophisticated material-balance scoring that adapts to the
peculiarities of endgames with reduced material, and
3. the integration of perfect knowledge (e.g. interior-node
recognizers, knowledgeable endgame databases) into the search
as described in Part II of my book "Scalable Search in Computer
Chess" (http://supertech.lcs.mit.edu/~heinz/node1.html).
=Ernst=
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