Author: Martin Giepmans
Date: 08:27:46 12/30/02
Go up one level in this thread
On December 30, 2002 at 07:08:27, Ed Schröder wrote:
>On December 30, 2002 at 05:53:16, Martin Giepmans wrote:
>
>>On December 30, 2002 at 05:30:45, Ed Schröder wrote:
>>
>>>As it seems I have completely mishandled explaining Reduction 2b and 2c, I have
>>>corrected things.
>>>
>>>http://members.home.nl/matador/chess840.htm
>>>
>>>Click on the blue "update" picture, it will move you directly to the changes
>>>made. That will be standard procedure from now on in case of errors.
>>>
>>>if (remaining_depth<=x && remaining_depth>1) then
>>> { if (ALPHA < SCORE + THREAT) -> do not reduce
>>> if (ALPHA < SCORE + THREAT + MARGIN) -> reduce depth with one ply. }
>>>
>>> SCORE : score of EVAL
>>> THREAT : Queen=900, Rook=500, Bishop=300, Knight=300, Pawn=100
>>> MARGIN : TABLE [remaining_depth];
>>>
>>> static int TABLE[]= { 00,00,10,15,20,25,25,25,25,25,25,25,25,25,
>>> 25,25,25,25,25,25,25 ........... };
>>>
>>>The idea is, if SCORE+THREAD are not going to make it to ALPHA, but with an
>>>extra small MARGIN it will then reduce the depth. I can't remember the speed-up
>>>this reduction gave.
>>>
>>>====
>>>
>>>Ed
>>>
>>>PS, the "faulty stuff" plus Uri's correction is maybe worth a try, who knows :)
>
>>The < in the second formula should be > ?
>>Otherwise the two formula's together don't make sense.
>>(if the first is true, the second is also true)
>
>For free-style pseudo code it is defendable, maybe in more c-code style would
>make it more clear?
>
> { if (ALPHA > SCORE + THREAT &&
> ALPHA < SCORE + THREAT + MARGIN) -> reduce depth with one ply. }
Yes, this makes it more clear.
However, I wonder if the second part of the condition (the margin part)
is useful. Maybe it is if the current window is smaller than margin, but
otherwise?
Of course, the extra condition makes the tric safer, but I think it could
also cause more search instability.
BTW, this probably doesn't work in an engine that uses PVS.
Am I right?
Cheers,
Martin
>
>ALPHA=100
>SCORE=90
>THREAT=0
>MARGIN=20
>
>-> reduction
>
>ALPHA=100
>SCORE=60
>THREAT=0
>MARGIN=20
>
>-> no reduction
>
>Ed
>
>
>>Martin
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