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Subject: Re: Crafty-IsiChess,CCT4,r11 ==> A move to avoid?

Author: Uri Blass

Date: 14:52:45 01/30/02

Go up one level in this thread


On January 30, 2002 at 17:02:28, Miguel A. Ballicora wrote:

>On January 30, 2002 at 16:11:07, Uri Blass wrote:
>
>>On January 30, 2002 at 15:22:09, Gerd Isenberg wrote:
>>
>>>>Are we sure that this blind spot is caused by null move? I tried switching
>>>>off null move completely and it makes very little difference to what my program
>>>>does in this position. My score still starts out at -1.something for black then
>>>>goes to +1.something, then goes back to -1.something before drifting back up to
>>>>around +0.9, all in the first 5 minutes of search (up to depth 20). Does anyone
>>>>else find that null move doesn't make much difference here? Obviously using null
>>>>move helps with the number of nodes, but it doesn't change the scores very much
>>>>at all.
>>>>
>>>>Andrew
>>>
>>>Use the position one move before. This position should be Nullmove sensitive:
>>>
>>>[D] 8/8/1p1r1k2/p1pPN1p1/P3KnP1/1P6/8/3R4 b - - bm Nxd5
>>>
>>>If i use Nullmove here, but no confirmation-Search, IsiChess finds Nxd5 in about
>>>three minutes.
>>
>>I do not understand it.
>>
>>How is it possible to find Nxd5 with null move pruning without confirmation
>>search?
>>It seems impossible to do it.
>
>I do not know what a confirmatory search is (I guess I can imagine, something
>like YACE) but I think of 3 possible ways:
>1) reduce depth, rather than pruning (Gaviota)
>2) double nullmove (Diep)

I am not sure if I understand the meaning of confirmation search but 1 and 2
seem to me similiar to confirmation search.

I understand that confirmation search means searching to reduced depth and only
if you find a zunzwang search to full depth.

1 is similiar to confirmation search and the only difference may be that in 1
you never search to full depth after searching to reduced depth.

2 is also basically the same as 1 because you search the line  null null to a
reduced depth.

>3) apply only nullmove when depth is < x plies. x could be something like 7 etc.
>This one I think is Crafty, according to some posts in the past (IIRC).

I do not know but I think that it is not in Crafty.
Crafy falled into the trap.

I also do not think that 3 is a good idea.
you can save a lot of time by pruning moves that are close to the root and has
no threat.

Uri



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