Author: Tim Foden
Date: 08:12:35 11/13/01
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On November 13, 2001 at 10:03:39, Dieter Buerssner wrote: >Thanks a lot Paul. > >Did Ernst A. Heinz comment on some unusual cases? For example this nice position >from Tarrasch, "Das Schachspiel": > >[D] 4N3/8/6p1/8/8/7p/5K1k/8 b - - > >1...Kh1 2. Nf6 Kh2 3. Ng4+ Kh1 4. Kf1 g5 5. Kf2 h2 6. Ne3 g4 7. Nf1 g3+ 8. Nxg3# >(White to move, also wins) > >The mate position is KNKP, where in your list this is not considered. No, doubt, >this will not play a role in practical games. However it leaves a (very small) >ungood feeling, when you know, that you make your program purposley blind for >some special study like positions. I think, this would be no problem for an eval >function, to give N vs. P(s) allways a positive score for the P (which I am >actually doing). This will heal itself by the search. However, when you cut in >the search too early, it will be blind for this forever. > >BTW. If you ever should be the black side of this position on an internet chess >server. Just don't move. After some time, you will see the message: "game drawn, >Black runs out of time, and White has not enough mating material", or similar >:-) > >Did Heinz also mention, how he handles the stalemate problem for the "allways >won" cases? > >And at last, I have found a very small improvement. For w/d/l cases, it seems to >be assumed, that 4 positions are encoded in one byte, while it is possible, to >store 5 positions in the same space. > >Regards, >Dieter Hi Deiter, Hienz's book says the following about the KNKP engame table "KBKP, KNKP. The endgames KBKP and KNKP are generally drawn. Nevertheless, there exist hundreds of thousands of KBKP / KNKP positions that represent wins for the KP side. Because these KP wins evade and easy recognition, we encode them as database values with a single bit per position (see Table 6.1): 0 = KP side does not win, 1 = KP side wins. The remaining exceptions of non-drawn KBKP / KNKP position occur if the KB / KN side has the rare opportunity to let its single minor piece mate the opponent. We handle the exceptional positions by means of a few recognition rules (see Section 6.4) which require no more database values for our knowledgeable encoding of KBKP and KNKP." The book makes interesting reading. :) Cheers, Tim.
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