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Subject: Re: null move+PVS question

Author: Volker Böhm

Date: 11:08:35 11/12/04

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Hi,

I am no good chess player, but I analyzed the game with spike. Spike does find
c1f1 at ply 5 but takes until ply 8 to find a score of two pawns for white
(result is below).
The result is ugly as at ply 6 you´ll see a large search instability. The
analyse  of spike´s game tree shows the instability comes from nullmove.

After 35.Rc1-f1 Qf5-g5 36.Qb3-d3 we have a position where black has no good move
to protect the loss of a piece for a pawn. White needs two moves to win the
piece. The nullmove will reduce the amount of white moves. Thus he will find the
win later.
Black has no move to protect for a nearly forced loss of material. I have seen
those positions very rarely.

Greetings Volker



Spike034 [001]  WB2 37 MB:
 1   00:00  0,28   1. g1h1
 2   00:00  0,05   1. g1h1 f5f2
 2   00:00  0,16   1. a3a4 e8d8
 2   00:00  0,29   1. c1f1 f5g5
 2   00:00  0,29   1. b3c2 f5g5
 3   00:00  0,34   1. b3c2 f5g5 2. c2e4
 3   00:00  0,38   1. c1f1 f5g5 2. g2e4
 4   00:00  0,29   1. c1f1 f5g5 2. b3a4 e8e7
 4   00:00  0,35   1. b3b1 f5b1 2. c1b1
 5   00:00  0,15   1. b3b1 f5b1 2. c1b1 f6g5 3. b1e1 h7h6
 5   00:00  0,38   1. c1f1 f5g5 2. b3a4 e8e7 3. g2e4
 6   00:00  0,68   1. c1f1 f5g5 2. b3d3 e8d8 3. e3e4
 6   00:00  0,33   1. c1f1 f5g5 2. b3d3 e8d8 3. e3e4
 7   00:00  0,63   1. c1f1 f5g5 2. b3d3 e8d8 3. e3e4
 7   00:00  0,62   1. c1f1 f5g5 2. b3d3 e8d8 3. e3e4
 8   00:00  0,92   1. c1f1 f5g5 2. b3d3 e8d8 3. e3e4
 8   00:01  1,99   1. c1f1 f5g5 2. f1f2 e8d8 3. e3e4 g5h5 4. b3a4 d5f4
 9   00:01  1,99   1. c1f1 f5g5 2. f1f2 e8d8 3. e3e4 g5h5 4. b3a4 d5f4 5. d2f4




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