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Subject: Re: A test position for chess programs

Author: Howard Exner

Date: 15:53:46 12/29/00

Go up one level in this thread


On December 29, 2000 at 12:00:41, Uri Blass wrote:

>This position is similiar to the position that crafty had no problem to solve
>
>[D]R7/8/6k1/4n3/5p2/5P2/5r1p/7K b - - 0 1
>
>The test is to avoid Nxf3 that is leading to a draw.
>Another test is to see the draw after Nxf3.

Again I tested Tiger13, Century3 and Crafty17.14.
In the original where Kf5 was the best move Crafty's time was 1:16, Rebel's was
8:42 and Tiger's was unsolved after 10 minutes.

For this revised position Rebel is 2:55, Crafty 6:20, and Tiger unsolved after
10 minutes. Athlon 900. None post a draw score. Crafty's score cange from
Nxf3 to Rxf3 is a miniscule .01
00:02:59.4	-7.26	15	77073974	Nxf3 Ra6+ Kg5 Rg6+ Kf5 Rf6+ Ke5 Rf5+ Kd6 Rf6+ Kc5
Rf5+ Kb6 Rf6+ Kb5 Rf5+ Ka6 Rf6+ Kb7 Rf7+ Kc6 Rf6+ Kd5 Rxf4

00:06:20.5	-7.27	15	208372603	Rxf3 Kxh2 Ng4+ Kg2 Rg3+ Kh1 Rd3 Rg8+ Kh5 Rh8+ Kg5
Rg8+ Kh4 Re8 Kg3 Re1 Nf2+ Kg1 Nh3+ Kf1 f3

Rebel's is a greater change of about 1.00. Can get the exact numbers if you
want.

Might a clue to handling this position be reducing the eval when detecting that
the defending side can check perform rook checks directly beside the enemy king
( ie checking Rf6 when the king is on f5) over a series of checks?
Playing the odds as I'm sure there are exceptions when the king can move to a
spot where the perpetual checks cease, but usually these draws hold up.



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