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Subject: Re: Another example of very deep tactics that Computers cannot solve

Author: John Merlino

Date: 11:35:00 12/07/01

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On December 07, 2001 at 12:48:22, ALI MIRAFZALI wrote:

>The following position occured in one of the oldest Correspondence games
>played in America:
>[D] 2kr3r/ppp2ppp/1b3nq1/4p2b/1PB1P3/2P1B3/P1QN1PPP/R4RK1  b   - 0 1
>This game was played in 1840.
>Here black played 15...Rxd2!! Game finished with 16.Qxd2 Nxe4 17.Qc1 Bf3
>18.g3 h5! 19.Bd5 h4 20.Bxe4 Qxe4 21.Bxb6 Qg4 22.Qe3 axb6 23.R(f)-b1  e4
>24.Qe1 f5! 25.Rb2 f4 26.R(a)-b1  Black announced Mate in Some number of moves.
>Fritz 6 and chessmaster 8000 donot see 15...Rxd2!! No matter how long one runs
>the position.
>Does your program see 15...Rxd2!!!.Althuogh Tactics is the area that Computers
>are naturally strong ;it is interesting that one still runs into tactical
>positions which programs cannot solve.Please indicate your result.

Here's what Chessmaster 8000 sees. It seems quite happy with 15...Bxe3.

Time	Depth	Score	Positions	Moves
0:00	1/3	-0.51	1420		1...Bxe3 2.fxe3 Qg5 3.Rae1 Kb8
0:00	1/4	-0.42	3143		1...Bxe3 2.fxe3 Qg5 3.Rae1 Kb8
					4.Bb5
0:00	2/5	-0.48	13872		1...Bxe3 2.fxe3 Qh6 3.Rfe1 Qg5
					4.Bb5 Kb8
0:00	2/6	-0.43	35005		1...Bxe3 2.fxe3 Qh6 3.Rfe1 Kb8
					4.Bb5 c6
0:02	3/7	-0.63	171727		1...Bxe3 2.fxe3 Qg5 3.Rfe1 Kb8
					4.a4 Rhe8 5.Bb5
0:06	3/8	-0.54	415527		1...Bxe3 2.fxe3 Qg5 3.Rfe1 Kb8
					4.a4 Rhe8 5.Bb5 c6
0:24	4/9	-0.71	1686226		1...Bxe3 2.fxe3 Rd7 3.Rf2 Rhd8
					4.h3 Qg5 5.Re1 Qg3 6.Nf1 Qh4
1:08	4/10	-0.63	5029749		1...Bxe3 2.fxe3 Rd7 3.Rf2 Rhd8
					4.h3 Qg3 5.Nf1 Qh4 6.Bb5 c6
4:56	5/11	-1.08	22907929	1...Bxe3 2.fxe3 Qg5 3.Rfe1 Rd7
					4.Nf1 Rhd8 5.Bb5 c6 6.Be2 Bg6 7.Bf3
					Qh4

It appears that the hard move for CM8000 to find is 18...h5. Even after setting
up that position, CM8000 doesn't find it in a five minute search on my PIII-600.
It does find 18...Rd8, however, which it is eventually happy with:

Time	Depth	Score	Positions	Moves
0:00	1/3	-0.51	1347		4...Qc6 5.Bxb6 Qxc4
0:00	1/4	-0.48	3077		4...Qc6 5.Bxb6 Qxc4 6.Qe3 Qxc3
					7.Bxa7
0:00	2/5	-0.48	11825		4...Qc6 5.Bxb6 Qxc4 6.Qe3 Qxc3
					7.Bxa7
0:01	2/5	-0.96	33888		4...Qf5 5.Re1 Nxf2 6.Kxf2 Bd5+
					7.Kg1 Bxc4 8.Bxb6 axb6
0:01	2/6	-0.58	40996		4...Qf5 5.Re1 Nxf2 6.Bxf2 Bxf2+
					7.Kxf2 Bd5+ 8.Kg1 Bxc4 9.Qe3
0:02	3/7	-0.58	114102		4...Qf5 5.Re1 Nxf2 6.Bxf2 Bxf2+
					7.Kxf2 Bd5+ 8.Kg1 Bxc4 9.Qe3
0:07	3/8	-0.22	524430		4...Qf5 5.Re1 Nxf2 6.Bxf2 Bxf2+
					7.Kxf2 Bd5+ 8.Kg1 Bxc4 9.Qe3 Re8
					10.Qxa7
0:14	3/8	-0.32	1035443		4...Rd8 5.Re1 Kb8 6.a4 Nd6 7.Qd2
					Qe4 8.Bxb6 Qxc4
1:02	4/9	-0.50	4534803		4...Rd8 5.Re1 Rd2 6.Bxd2 Bxf2+
					7.Kf1 Bxg3 8.Rxe4 Bxh2 9.Bg5 Qxe4
					10.Kf2 Qg4 11.Bxf7
4:01	4/10	-1.13	18891292	4...Rd8 5.Re1 Rd2 6.Qxd2 Nxd2 7.Bxd2
					Qc2 8.Be3 Qxc3 9.Rac1 Qxb4 10.Bxb6
					axb6 11.Rxe5

From my testing, it appears that CM8000 would find the move once it reached
depth 18. But this could take many hours.

After 26.Rab1, it is a Mate in 4.

jm



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