Author: Vincent Diepeveen
Date: 09:32:58 12/30/02
Go up one level in this thread
On December 30, 2002 at 12:29:59, Martin Giepmans wrote:
>On December 30, 2002 at 11:38:18, Vincent Diepeveen wrote:
>
>>On December 30, 2002 at 11:27:46, Martin Giepmans wrote:
>>
>>>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?
>>
>>Wrong.
>>
>>This doesn't work in an engine using nullmove. Unless you only test tricks.
>>the smaller you make margin the more you positionally are going to miss.
>
>Thank you very much, Vincent.
>I was asking a question about PVS, not about nullmove.
>
>Martin
PVS is independant from your question. Nullmove and hashtables
are a big influence though.
>
>>
>>The whole pruning system of Ed has a major focus upon not missing tactics.
>>
>>That was of course worth a world title in Madrid start of the 90s.
>>
>>It is a very ingenious system.
>>
>>Nowadays we have nullmove.
>>
>>Nevertheless it gives good ideas to me to work on some forward pruning
>>experiments in the future.
>>
>>>
>>>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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