Author: Martin Giepmans
Date: 09:29:59 12/30/02
Go up one level in this thread
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
>
>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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