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Subject: Re: Null move? Pruning?

Author: Ralf Schäfer

Date: 03:26:29 02/01/04

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On January 31, 2004 at 19:29:18, Jaime Benito de Valle Ruiz wrote:

>I came across this position almost by accident. A few moves before this, my
>"poor engine" was giving a huge score for white in no time, while Ruffian
>sticked to draw. So I reanalized the whole thing.
>Why can't Ruffian 1.05 find an easy 1.Qd5 and win? Null move? Special Pruning?
>
>[d]Q7/8/1p1K4/1p6/2k5/8/1P6/4q3 w - -
>
>Ruffian_105  UCI 60 MB:
>D1  00:00  -2.11   b2b3 Kc4xb3
>D1  00:00  -0.98   Kd6c6
>D1  00:00  -0.24   Qa8c6 Kc4b4 Qc6xb6
>D2  00:00  -0.24   Qa8c6 Kc4b4 Qc6xb6
>D2  00:00  -0.16   Qa8d5 Kc4b4 Kd6c6 Qe1e3 Qd5xb5
>D2  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D3  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D4  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D5  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D6  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D7  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D8  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D9  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D10  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D11  00:00  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D12  00:01  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D13  00:04  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D14  00:08  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D15  00:17  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D16  00:33  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D17  01:04  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2
>D18  02:02  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2

My Engine Cheetah seems not to have a problem with this position. It sees Qd5 at
Play 2, giving it a winning score at ply 5.

Cheetah 0.70 CCT6 Build 4  WB2
 1   00:00 -9,70   Da8e8
 1   00:00 -1,00   Da8d8
 1   00:00 -0,60   Da8c8+ Kc4d4
 2   00:00 -1,00   Da8c8+ Kc4b3 Dc8f5
 2   00:00 -0,60   Da8g8+ Kc4b4 Dg8g4+ Kb4b3
 2   00:00  0,40   Da8d5+ Kc4b4 Kd6c6 De1e2
 3   00:00  0,20   Da8d5+ Kc4b4 Kd6c6 De1c1+ Kc6xb6 Dc1f1
 4   00:01 -0,20   Da8d5+ Kc4b4 Kd6c6 De1c1+ Kc6xb6 Dc1f1 Dd5d7
 5   00:01  6,69   Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4c3 Da3xc1+
Kc3xb3
 6   00:01  7,57   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Kd6c6 b5b4
 7   00:01  7,07   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Kd6c6 b5b4 Kc6xb6
 8   00:01  7,69   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Kd6c6 Kb3b4 Da1a7 Kb4c4
 9   00:01  7,69   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Da1b1+ Kb3c4 Db1f1+ Kc4b4 Kd6c6 Kb4a5
10   00:01  7,71   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Kd6c6 b5b4 Kc6b5 Kb3c2 Kb5xb4 Kc2d3
11   00:02  8,71   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Da1b1+ Kb3c4 Db1f1+ Kc4b4 Kd6c6 Kb4b3 Kc6xb5 Kb3c2
12   00:04  8,71   Da8d5+ Kc4b4 Dd5d3 De1a1 Dd3c3+ Kb4a4 b2b3+ Ka4a3 Dc3xa1+
Ka3xb3 Da1b1+ Kb3c4 Db1f1+ Kc4b4 Kd6c6 Kb4c3 Kc6xb5 Kc3c2 Df1e2+ Kc2c3
13   00:28  10,17   Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4d3 Da3xc1
b5b4 Kd6c6 b6b5 Kc6xb5 Kd3d4 Kb5xb4 Kd4e4 Dc1b1+ Ke4f4
14   00:37  10,33   Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4d3 Da3xc1
b5b4 Dc1c4+ Kd3e3 Dc4xb4 b6b5 Db4xb5 Ke3f2 b3b4 Kf2g3 Db5d3+ Kg3g4
15   00:49  10,33   Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4d3 Da3xc1
b5b4 Dc1c4+ Kd3e3 Dc4xb4 b6b5 Db4xb5 Ke3f2 b3b4 Kf2g3 Kd6c6 Kg3g4
16   02:33  10,49   Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4d3 Da3xc1
Kd3e2 b3b4 Ke2d3 Kd6c6 Kd3e2 Kc6xb5 Ke2d3 Kb5xb6 Kd3e2 b4b5 Ke2d3
17   06:29  M12  Da8d5+ Kc4b4 Dd5d3 De1c1 Dd3a3+ Kb4c4 b2b3+ Kc4d3 Da3xc1 Kd3d4
b3b4 Kd4e4 Kd6e6 Ke4d4 Dc1d2+ Kd4c4 Ke6e5 Kc4b3 Ke5d4 Kb3a4
17   06:29  M12  (HSize 16777215 HFull 2230264 HHits 60799807 HReps 3237880
HCols 367989 NSearch 45749692 NQuiesce 30180709 SelDepthSearch 30
SelDepthQuiesce 31)

Best
Ralf





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