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Subject: Re: end-game teaser

Author: Uri Blass

Date: 23:35:22 01/23/05

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On January 24, 2005 at 01:40:44, Will Singleton wrote:

>[d]8/5p2/6p1/5k1p/5P1P/6PK/5rB1/8 b - - bm Rxg2
>
>Amateur finds this in < 3 sec, faster than some others.  A null-move issue?
>
>14 255 198 911657 Rc2 Bd5 f6 Bf7 Rb2 Bd5 Re2 Bc6 Rd2
>15 255 236 1091636 Rc2 Bd5 f6 Bf7 Rb2 Bd5 Re2 Bc6 Rd2
>15 328 277 1280278 Rxg2 Kxg2 Kg4 Kf2 Kh3 Kf3 f5 Kf2 Kh2 Kf3 Kg1 g4 hxg4
>16 264 289 1341561 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf4 Kg2 Kxf5 Kxg3
>17 334 312 1455185 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf4 Kg2 Kxf5 Kxg3
>18 344 340 1592589 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf2 Kg4 Kg2 f4
>19 348 389 1826593 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf2 Kg4 Kg2 f4
>20 348 457 2147297 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf2 Kg4 Kg2 f4
>21 431 569 2673404 Rxg2 Kxg2 Kg4 Kf2 Kh3 f5 gxf5 Kf3 f6 Kf2 Kg4 Kg2 f4

No null move because almost no program use null move pruning in pawn endgames.

I guess that it is evaluation issue and most programs do not have special
evaluation for pawn endgame and they need some plies to evaluate the following
lines as more than +2.5 for black

Rxg2 Kxg2 Kg4 Kf2 Kh3 Kf3 f5 Kf2 Kh2 Kf3 Kg1 g4

Movei needs 6 plies after the following line to see a score that can convince it
to play Rxg2.

Uri



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