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Subject: Re: Engine Test.........Mate in 23

Author: John Merlino

Date: 10:27:07 03/05/05

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On March 05, 2005 at 12:19:53, Rob Basham wrote:

>[D]r1bqr3/pp1k2pp/3b1n2/4R1Bn/2Q1P3/P1N5/1PP2PPP/1B1R2K1 w - - 0 1
>
>Fritz 8 takes about 58 seconds to find..
>Rxd6+...!
>
>This move mates in about 23 moves..not sure...:-)
>
>If any program announces mate at move one, that would be exciting too...
>
>rob

CMX Yoda v25 finds Rxd6+ in two seconds on a P4-2.4, but there is no mate
announcement after more than 10 minutes.

After forcing:

1.Rxd6+ Kxd6 2.Qc5+ Kd7 3.Rd5+ Ke6 {Nxd5 leads to a mate in no more than twelve
moves} 4.Rxd8 Ke7 {the only move that does not lead to a quick mate}

...things get a bit fuzzy. There are four potential best moves here: Rxc8, Bxf6,
Ba2+ and Rxe8 -- all of which lead to very high scores.

[D]r1bRr3/pp3kpp/5n2/2Q3Bn/4P3/P1N5/1PP2PPP/1B4K1 w - - 0 5

So, it took a little while, almost 20 minutes, but we (Yoda and I :-) finally
got this:

Time	Depth	Score	Positions	Moves
0:00	1/5	14.57	25939		5.Ba2+ Be6 6.Bxf6 Raxd8 7.Bxd8
					Bxa2 8.Qxh5+ Kf8
0:00	1/6	14.67	96330		5.Ba2+ Be6 6.Bxf6 Raxd8 7.Bxd8
					Bxa2 8.Qxh5+ Kf8 9.Bc7
0:01	1/7	14.91	280990		5.Ba2+ Be6 6.Bxf6 Raxd8 7.Bxe6+
					Rxe6 8.Bxd8 Nf4 9.Qxa7
0:03	1/8	14.87	845889		5.Ba2+ Be6 6.Bxf6 Raxd8 7.Bxe6+
					Kxe6 8.Qf5+ Kf7 9.Bxd8+ Kg8 10.Bg5
					g6
0:05	1/8	15.05	1182525		5.Bxf6 Nxf6 6.Ba2+ Kg6 7.Rxe8 Nxe8
					8.Qe7 Nf6 9.Bf7+ Kh6 10.Qe5 Bf5
					11.Qxf5
0:07	1/9	16.46	1865439		5.Bxf6 Nxf6 6.Ba2+ Kg6 7.Rxe8 Nxe8
					8.h4 h6 9.h5+ Kh7 10.Qf8 Nf6 11.Bf7
					Bf5 12.Qxa8
0:16	1/9	17.16	4054262		5.Rxc8 Kg8 6.Rxa8 Rxa8 7.e5 Re8
					8.Bd2 b6 9.Qd4 Re6 10.exf6 Nxf6
0:19	1/10	17.58	4988993		5.Rxc8 Kg8 6.Rxa8 Rxa8 7.e5 Re8
					8.Be3 a6 9.g4 Kh8 10.gxh5
0:43	1/11	18.55	11578240	5.Rxc8 Kg8 6.Rxa8 Rxa8 7.e5 Re8
					8.Ba2+ Kh8 9.Bf7 Ra8 10.Qd6 h6
					11.exf6 hxg5 12.Bxh5
1:41	2/12	18.86	28921154	5.Rxc8 Kg8 6.Rxa8 Rxa8 7.e5 Kh8
					8.exf6 gxf6 9.Bxf6+ Nxf6 10.Qe5
					Rf8 11.Qe7 Nd7 12.Qxd7 b6 13.Qxa7
5:25	2/12	26.08	96936342	5.Rxe8 Kxe8 6.Ba2 Nf4 7.Bxf4 Be6
					8.Bxe6 Rd8 9.Qc7 Rd7 10.Bxd7+ Nxd7
					11.Bd6 g5 12.Qc8+ Kf7 13.Qxd7+
					Kg6 14.Qxb7
19:48	2/13	Mate12	381094649	5.Rxe8 Kxe8 6.Ba2 Bg4 7.Nd5 Nxd5
					8.Qxd5 Nf6 9.Qf7+ Kd8 10.Qxg7 Kc8
					11.Qxf6 Kd7 12.Qe7+ Kc6 13.Bd5+
					Kb6 14.Qxb7+ Ka5 15.Qb4+ Ka6 16.Bc4#

So, I have determined that Rxd6 leads to a mate in no more than 16 moves.

jm



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