Author: Ed Schröder
Date: 10:40:39 12/30/02
Go up one level in this thread
On December 30, 2002 at 08:03:44, Tony Werten 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. }
>
>I don't get this one.
>
>I would expect:
>
>1) score+threat>alpha : OK you have some threat, don't reduce
>
>2) score+threat+margin>alpha: You have a threat, if you win it and and get some
>positional advantage you could end up above alpha so to be safe don't reduce.
You are thinking the wrong way, from the page:
"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."
As said to Martin there is little logic in the idea, but let's take an example,
[d]rnbqkbnr/ppp2ppp/3p4/4p3/2B1P3/8/PPPP1PPP/RNBQK1NR w KQkq -
In this position white might have 1.d4 as best move, ALPHA being 0.30 or so.
Moves like 1.Bf1 1.a3 1.a4 will not make it to ALPHA, but with the MARGIN
probably will, thus the reduction is rewarded.
You should just try it and see if it is useful, if not bad luck, what's new?
Ed
>3) score+threat+margin: No (good) threats, even with something added you're
>still not close to alpha so reduce.
>
>You seem to have swapped the reduction conclusions from 2 and 3. What's the idea
>? Is it that 3 will be reduced anyway later on, and you want to add some
>reductions to 2 ?
>
>Cheers,
>
>Tony
>
>>
>>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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