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

Author: Gerd Isenberg

Date: 12:22:09 01/30/02

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>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. With conditional confirmation-Search (depth to leaf and some
more), it finds it in two seconds, without Nullmove in 0.2 seconds.

In the position after ...Nxd5 Rxd5 (with cleared HT) Nullmove makes not so much
difference here, Re6 becomes best move very fast in any case! It seems, there is
nothing to prune after Re6 at ply one, at least in our Nullmove implementations
(may be in yours depending on odd/even effects, beause of the oscillation?).
White has already the material gain at the root, possibly triggered the Nullmove
Failhigh the Position before (at ply 3).

Gerd






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