Author: blass uri
Date: 17:26:08 10/02/98
Go up one level in this thread
On October 02, 1998 at 18:36:45, Robert Hyatt wrote: >On October 02, 1998 at 15:23:11, blass uri wrote: > >> >>On October 02, 1998 at 13:12:02, Robert Hyatt wrote: >> >>> >>>In this position. crafty says Be4+ Mat34, with a 2 second search. How did >>>it do that? like this: >>> >>> 8 2.03 Mat34 1. Be4+ Ka7 2. Bxb8+ Ka6 3. Bb7+ Qxb7 >>> 4. Rxb7 Kxb7 >>> 8-> 3.27 Mat34 1. Be4+ Ka7 2. Bxb8+ Ka6 3. Bb7+ Qxb7 >>> 4. Rxb7 Kxb7 >>> >>>What it did was to search deeply enough to see that it could trade bishop >>>and rook for the opponent's rook and queen, leaving it in a KBN vs K position. >>>And after searching the 8 plies into the future (as it did above) it then found >>>the endgame database position and said "aha, Mate in N from this point." >> >> >>> >>>This is why my current version (15.21) won't play Rxb2, because it can see >>>deeply enough into the future to see the white king eating the black pawns >>>and that gives "mate in N". >> >>If it could see this then without tablebases the evaluation was instead of -0.xx >>big advantage for white because it could not see the mate but could see the >>position of KPP against K >> >> Or in some variations it sees one black and one >>>white pawn being traded, and that also leads to mate in N. >> >>I do not think that there are logical lines to go to KP against KP in the >>example that I gave >> >> >> >>Uri > > >Look at the final position in the short variation you gave. White's king >is 3 files closer to the pawns than the black king is, and black gets to >watch while the white king penetrates the black kingside and shreds it... > >So I'm not sure what you aren't "seeing" there... In the final position it is easy to see that white is winning the problem is in the position before trading rooks. I checked the position with crafty after Rxb2 Kxb2 without tablebases and it needs to go 18 plies deep to see that the position is worse than -2.xx It is easy to compute many plies deep in a pawn ending but the real problem is before the pawn ending and I do not understand how hash tables can help and how can you compute 15 plies deep in rook ending when my pentium200MMX cannot finish 12 plies in 20 minutes. Uri
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