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Subject: Re: Another tough mate in 5... or is it 4? (with analysis)

Author: Stan Arts

Date: 06:11:48 10/17/03

Go up one level in this thread


>>[D] 2br1R1R/8/1Ppp1br1/3B1k1P/Q1NP1P2/1N4BP/2P5/2Kn4 w - -
>>
>>   I got this one from the back pages of "Blackburne's Chess Games".
>> Interesting, because Blackburne himself claims a mate in 4.
>> This is his solution:
>>  1 Rh6 Rxh6
>>  2 Nc5 cd
>>  3 Qe8 Any
>>  4 white mates accordingly (his words).
>> I have'nt gone over it to find out where Blackburne went wrong, but
>> this is what CM9K with ss=0 has to say.
>>
>>  Lyn

Hi Lyn

Neurosis 1.4(next version) on slow pIII-550 with 64MB hash.

Legal moves: 49
Ply Score Time     Nodes      Best move and expected line
------------------------------------------------------------
2   2085  0        862        Rxf6+ Kxf6 Rxd8
3   2085  0        1127       Rxf6+ Kxf6 Rxd8
3   2112  0        1262       hxg6 < + > Nc3 Rxd8
3   2312  6        1557       hxg6 Rxf8 Rxf8
4   2268  39       30304      hxg6 < - > Rxf8 Bf3 Ke6
4   2176  44       33960      hxg6 Rxf8 Nxd6+ Kxg6 Rxf8
5   2226  143      116387     hxg6 < + > Bd7 Rxd8 Bxd8
5   2231  165      136481     hxg6 Rxf8 Rxf8 cxd5 Kxd1
6   2191  967      772187     hxg6 < - > Rxf8 h4 cxd5
6   2177  1066     852526     hxg6 Rxf8 Rxf8 cxd5 Nxd6+ Kxg6 Qe8+ Kh6
6   2178  3422     2681609    Qa7 < + > Be6 hxg6 Bc8
6   2269  3532     2782776    Qa7 cxd5 Qf7 Ke4 Qxg6+ Kf3 Rxd8
7   2269  4263     3341260    Qa7 cxd5 Qf7 Ke4 Bf2 Kf3
7   2270  6471     5215378    Qxc6 < + > Be6 hxg6 Rb8
7   2336  7124     5796998    Qxc6 Rxg3 Nxd6+ Kxf4 Rxf6+ Ke3 Rxd8
7   2349  15616    13106642   Rh6 < + > Rd7 hxg6 Nb2
7   2599  15934    13408438   Rh6 < + > c5 hxg6 Rd7
7   9991  19241    16197863   Rh6 (Mate in 5) Bb7 Rxg6 cxd5 Rf8xf6+ Ke4 Nc4-d2+
Ke3 Re6+
8   9991  35268    29735582   Rh6 (Mate in 5) Bb7 Rxg6 cxd5 Rf8xf6+ Ke4 Nc4-d2+
Ke3 Re6+
Total nodes:49502916 n/sec:83203  (Q-nodes:1429662 max depth:19)

And to "prove" there is no mate in 4, I let it do a brute force search (but with
check-
extentions etc.) on the position. And it doesn't return a mate in 4 in the depth
a mate
in 4 would be found.

2   2085  0        862        Rxf6+ Kxf6 Rxd8
3   2085  0        1127       Rxf6+ Kxf6 Rxd8
3   2112  0        1262       hxg6 < + > Nc3 Rxd8
3   2312  0        1557       hxg6 Rxf8 Rxf8
4   2268  38       30304      hxg6 < - > Rxf8 Bf3 Ke6
4   2176  44       34068      hxg6 Rxf8 Nxd6+ Kxg6 Rxf8
5   2231  181      151962     hxg6 Rxf8 Rxf8 cxd5 Kxd1
6   2191  1758     1501593    hxg6 < - > Rxf8 b7 cxd5
6   2177  1878     1606392    hxg6 Rxf8 Rxf8 cxd5 Nxd6+ Kxg6 Qe8+ Kh6
6   2178  5311     4410824    Qa7 < + > Be6 hxg6 Re8
6   2269  5481     4565681    Qa7 cxd5 Qf7 Ke4 Qxg6+ Kf3 Rxd8
7   2269  7794     6525596    Qa7 cxd5 Qf7 Ke4 Qxg6+ Kf3 Rxd8
7   2270  17664    14550680   Qxc6 < + > Re8 hxg6 Nc3
7   2336  19702    16367054   Qxc6 Rxg3 Nxd6+ Kxf4 Rxf6+ Ke3 Rxd8
7   2339  58776    48918486   Rh6 < + > c5 hxg6 Be6
7   2589  58973    49106074   Rh6 < + > Bb7 Nc5 dxc5
7   9991  60616    50513232   Rh6 (Mate in 5) Bb7 Rxg6 cxd5 Rf8xf6+ Ke4 Nc4-d2+
Ke3 Re6+
8   9991  85969    70885976   Rh6 (Mate in 5) Bb7 Rxg6 cxd5 Rf8xf6+ Ke4 Nc4-d2+
Ke3 Re6+
Total nodes:73527817 n/sec:82158  (Q-nodes:1124017 max depth:18)

Stan




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