Author: Richard A. Fowell (fowell@netcom.com)
Date: 12:20:27 12/19/99
Go up one level in this thread
On December 18, 1999 at 22:16:31, Vincent Lejeune wrote:
>
>7b/8/kq6/8/8/1N2R3/K2P4/8 w - - 0 1
>
>White play and draw !
>
>Interresting to test Stalemate/zugzwang and repetition detection of programs
>
>(all my surprise effect has desappear now :'( )
Well, that's a tougher one that the first one, since it is one ply deeper.
I only tried this one on Chessmaster 6000 Mac on my 180 MHz 604e, since it
scored the best on the easier problem (tied for first at 15 seconds to score
the latter position "0").
Chessmaster 6000 Mac got your "good position":
7b/8/kq6/8/8/1N2R3/K2P4/8 w - -
in a hair over 70 minutes:
*** Chessmaster 6000 Mac - 180 Mhz 604e ****
Time Depth Score Moves
--------------------------------------------------------------
00:36:56 10 -3.63 d2-d4 a6-b5 e3-h3 h8-f6 a2-b2 b5-b4 h3-f3
00:46:49 11 -3.66 d2-d4 a6-b5 e3-h3 h8-f6 a2-b2 b5-b4 h3-d3
01:10:13 11 0.00 b3-d4 h8-d4 e3-a3 a6-b5 a3-b3 b5-c4 b3-b6
01:12:15 12 0.00 b3-d4 h8-d4 e3-a3 a6-b5 a3-b3 b5-c4 b3-b6
Here's the ranking on your earlier problem:
7b/8/kq6/8/3N4/4R3/K2P4/8 b - -
Chessmaster 6000 - score of "0" at 15 seconds (7 ply)
Chessmaster 4000 - score of "0" at 15 seconds (7 ply?)
HIARCS 7.0 - score of "0" at 190 seconds (11 ply)
MacChess 5.01 - score of 202 at 2 min 44 sec (13 ply) down from 680)
Screamer B42 - score of -0.6 at 22 min 13 seconds (13 ply)
(down from -8.22 )
***********************************************************
**** Warning - solution follows ***************************
**** (in case you want to find it yourself ) **************
***********************************************************
- 5 -
- 4 -
- 3 -
- 2 -
- 1 -
- Solution -
The reason that Nb3-d4! draws is that it forces the
exchange of the Black Queen for the White Rook.
The move has these features:
1) It unblocks White's rook on the 3rd rank, creating the
threat of Ra3+ followed by Rb3, forcing the trade of the
Queen for the Rook by skewer or pin.
2) It guards the e6 square, creating the threat of Re6 pinning
the Queen to the king and forcing the exchange of the Queen
to the King.
Most of Black's moves (e.g., any king move, any bishop move, or any
move of the Queen on the 6th rank or to the a,b,c files that does not
put the Queen en prise) are met by one of the above motifs -
Rook to a3, b3, or e6.
The most obvious Black response - Qxd4, results in either draw by perpetual
check, as White shuttles the rook amongst a3, b3, c3, or by the stalemate
sacrifice of Rd3!! if Black moves his King to the d file. Since Rd3 then
pins Queen to King, and the reponse Qxd3 stalemates White, this scenario
is covered.
The remaining try for Black is Qd8. The idea is to try to sneak the King
away from the barrage of Rook checks as the Rook shuttles between
a3 and b3 without allowing the pin/skewer of the Queen.
This try fails due to the power of the Knight and its forks
for most attempted exits. One can draw an iron wall of squares that the
King dare not step on:
a4 - since the rook will always check at a3 whenever the King moves
to a5, the only entry to that square, since:
b5 - is covered by the Knight, and moving from the King from a5 to
b4 - is met by Nc6+ forking the Queen, and White actually wins
c5 - is met by Ne6+ forking the Queen and winning for White
c6 - is covered by the Knight
c7 - is met by Ne6+ forking the Queen and Black will be hard pressed to draw
This only leaves c8 as a potential exit. But ...
Kc8 - is met by Rb8+! Kxb8, Nc6+ forking the Queen, and when the board
clears, it is a draw, as Black has only a Bishop (insufficient mating
material).
In conclusion, the two most interesting lines for:
7b/8/kq6/8/8/1N2R3/K2P4/8 w - -
are:
1. Nd4 Qxd4 2. Ra3+ Kb5 3. Rb3+ Kc4 4. Rc3+ Kd5 5. Rd3 Qxd3 *
1. Nd4 Qd8 2. Ra3+ Kb7 3. Rb3+ Kc8 4. Rb8+ Kxb8 5. Nc6+ Kc8 6. Nxd8 Kxd8 *
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