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Subject: Re: Null move? Pruning?

Author: Harald Lüßen

Date: 02:30:29 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
...
>D18  02:02  0.00   Qa8a2 Kc4b4 Qa2a3 Kb4c4 Qa3a2

My very poor (slow and maybe still buggy) engine does the same.

(ply, score, sec/100, nodes, PV)
 0    -72      0          2 Qa8-d5
 0    -42      0         11 Qa8-a2
 1    -42      0         13 Qa8-a2
 2    -46      0        126 Qa8-a2 Kc4-d3  b2-b3
 2    -40      0        175 Qa8-d5 Kc4-b4 Qd5-a2
 2    -12      0        274 Qa8-c6 Kc4-d3 Qc6xb5
 3    -65      0        953 Qa8-c6 Kc4-b4 Qc6xb6 Qe1-e8 Qb6-d4
 3    -53      0       1088 Qa8-d5 Kc4-b4 Qd5-d4 Kb4-a5  b2-b3
 3    -38      0       1695 Qa8-g8 Kc4-b4 Qg8-g4 Kb4-b3 Qg4-g2
 3    -12      0       1902 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a1
 4    -12      0       2370 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
 5      0      4       5075 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4
 6      0      9      12691 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2
 7      0     14      25707 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
 8      0     26      55147 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
 9      0     57     137692 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4
10      0    128     318917 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2
11      0    259     652067 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
12      0   1143    2776770 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
Qa2-a3
13      0   1892    4544282 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
Qa2-a3 Kb4-c4
14      0   3437    8227562 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
Qa2-a3 Kb4-c4 Qa3-a2
15      0   9892   22722218 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
16      0  19467   44458358 Qa8-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3
Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4
Qa2-a3 Kb4-c4 Qa3-a2 Kc4-b4 Qa2-a3

When I play Qd5 it sees a mate after 1 hour. And I don't trust the score.
I use adaptive null move pruning.

(ply, score, sec/100, nodes, PV)
 1     84      0          9 Kc4-b4 Qd5-d4
 2     35      0         47 Kc4-b4 Qd5-g2
 3     52      0        202 Kc4-b4 Qd5-a2 Qe1-e3
 4     56      0        746 Kc4-b4 Qd5-a2 Qe1-g3 Kd6-c6 Qg3-e3
 5    -87      3       4819 Kc4-b4 Qd5-a2 Qe1-g3 Kd6-c6 Qg3-e3
 5      0      3       4918 Kc4-b4 Qd5-d3 Qe1-e4 Qd3xe4 Kb4-b3
 6    -87      3       5939 Kc4-b4 Qd5-d3 Qe1-e4 Qd3xe4 Kb4-b3
 6     -6      4       9298 Kc4-b4 Kd6-c6 Qe1-e8 Kc6xb6 Qe8-b8 Kb6-c6 Qb8-e8
 7    -93      6      13341 Kc4-b4 Kd6-c6 Qe1-e8 Kc6xb6 Qe8-b8 Kb6-c6 Qb8-e8
 7     -8      9      18472 Kc4-b4 Kd6-c6 Qe1-e8 Kc6xb6 Qe8-b8 Kb6-c6 Qb8-c8
Kc6-d6
 8    -93     12      28358 Kc4-b4 Kd6-c6 Qe1-e8 Kc6xb6 Qe8-b8 Kb6-c6 Qb8-c8
Kc6-d6
 8    -19     17      39002 Kc4-b4 Qd5-d4 Kb4-a5 Qd4-d3 Qe1-b4 Kd6-e5 Qb4xb2
Ke5-d5  b5-b4
 9     -7     42      99231 Kc4-b4 Qd5-d4 Kb4-a5 Kd6-d5 Qe1-h1
 9    -93    129     268107 Kc4-b4 Qd5-d4 Kb4-a5 Kd6-d5 Qe1-h1
10    -65    200     450589 Kc4-b4 Qd5-d4 Kb4-a5 Kd6-c6 Qe1-h1 Kc6-c7 Qh1-h7
Kc7-d6 Qh7-h6 Kd6-d7 Qh6-h7 Kd7-d6 Qh7-h6 Kd6-d7 Qh6-h7 Kd7-d6
10    -93    410     874102 Kc4-b4 Qd5-d4 Kb4-a5 Kd6-c6 Qe1-h1 Kc6-c7 Qh1-h7
Kc7-d6 Qh7-h6 Kd6-d7 Qh6-h7 Kd7-d6 Qh7-h6 Kd6-d7 Qh6-h7 Kd7-d6
11    -77    925    2492214 Kc4-b4 Kd6-c6 Qe1-c1 Kc6xb6 Qc1-e3 Kb6-a6 Qe3-h6
Ka6-a7 Qh6-h8 Qd5-e4 Kb4-b3 Qe4-e3 Kb3-c4  b2-b3 Kc4-b4 Qe3-c1
11    -93   1239    3208832 Kc4-b4 Kd6-c6 Qe1-c1 Kc6xb6 Qc1-e3 Kb6-a6 Qe3-h6
Ka6-a7 Qh6-h8 Qd5-e4 Kb4-b3 Qe4-e3 Kb3-c4  b2-b3 Kc4-b4 Qe3-c1
12    -83   3329    9497139 Kc4-b4 Qd5-h5
12    -93   4235   11966063 Kc4-b4 Qd5-h5
13    -83   6901   19611793 Kc4-b4 Qd5-h5 Kb4-a5 Qh5-h2 Qe1-b4 Kd6-d7 Qb4-g4
Kd7-d6 Qg4-g6 Kd6-e5 Qg6-e8 Ke5-d4 Qe8-d7 Kd4-e4 Qd7-e6 Ke4-d4 Qe6-d7 Kd4-e4
Qd7-e6
13    -93   8785   23762024 Kc4-b4 Qd5-h5 Kb4-a5 Qh5-h2 Qe1-b4 Kd6-d7 Qb4-g4
Kd7-d6 Qg4-g6 Kd6-e5 Qg6-e8 Ke5-d4 Qe8-d7 Kd4-e4 Qd7-e6 Ke4-d4 Qe6-d7 Kd4-e4
Qd7-e6
14    -83  11473   31318839 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b4
14    -93  18701   51404514 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b4
15    -83  37829  115449584 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b4
15    -93  43739  131427831 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b4
16    -83  64254  198172462 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b3 Kd5-c5
Qb2-e5 Qa8-d5 Qe5xd5 Kc5xd5
16   -101  82395  240411979 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-a5 Qh4-d8 Ka5-a4 Qd8-a8 Ka4-b3 Kd5-c5
Qb2-e5 Qa8-d5 Qe5xd5 Kc5xd5
17    -91 123798  380511472 Kc4-b4 Qd5-h5 Qe1-d2 Kd6-c6 Qd2-c2 Kc6xb6 Qc2-f2
Kb6-c6 Qf2-f6 Kc6-d5 Qf6xb2 Qh5-h4 Kb4-b3 Qh4-e1 Kb3-a4 Qe1-d1 Ka4-a5 Kd5-e6
17      0 148957  435710910 Kc4-b4 Qd5-d3 Qe1-d2 Qd3xd2 Kb4-b3 Qd2-c3 Kb3-a2
b2-b4 Ka2-b1 Kd6-d5 Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5 Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5
Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5 Kb1-a2
18    -94 166681  490555663 Kc4-b4 Qd5-d3 Qe1-d2 Qd3xd2 Kb4-b3 Qd2-c3 Kb3-a2
b2-b4 Ka2-b1 Kd6-d5 Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5 Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5
Kb1-a2 Kd5-d6 Ka2-b1 Kd6-d5 Kb1-a2
18    -94 266081  767329483 Kc4-b4 Qd5-d3
19    -84 355693 1067485769 Kc4-b4 Qd5-d3 Qe1-a1 Qd3-c3
19 -15944 361554 1083095304 Kc4-b4 Qd5-d3 Qe1-a1 Qd3-c3

Retrieving all PV moves from the hash table has obviously failed.

Harald



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