Author: blass uri
Date: 12:17:43 10/09/98
Go up one level in this thread
On October 09, 1998 at 14:56:46, José de Jesús García Ruvalcaba wrote: >On October 09, 1998 at 13:04:53, John Coffey wrote: > >>On October 09, 1998 at 09:38:35, Robert Hyatt wrote: >> >>>On October 09, 1998 at 02:11:19, Jouni Uski wrote: >>> >>>>I have feeling, that using 3-5 pieces tablebases don't give any measurable >>>>rating gain - may be 2-10 points maximum = no real gain. >>>> >>>>Jouni >>> >>> >>>I would disagree here, as I see KRP vs KR regularly. In fact, in long >>>games on ICC, I'd bet I see this about every 10 games or so. Lonnie >>>can comment because he has played against Crafty a lot. And it is quite >>>often for two computers to end up a pawn up or down, in the ending, and >>>if one knows about this, it will win more, or draw when it should lose, >>>than without them. >>> >>>ditto for endings like KRB vs KR... where it knows to trade into that >>>when it can be drawn... >> >>Fritz5 has KRP vs KR and KQ vs KR. Not sure if it has anything else. >> >>I wanted to create a tablebase with all the possible K + 2 pawns (or less) >>vs all the K + pawn positions. I figured that the number of possible positions >>is around 489 million, but if I were to store it 2 bits per position >>(win/loss/draw/unknown) then I could get it in 128 megs. >> >>John Coffey > >To make a tablebase, you need all of its descendants first. The direct sons of >KPPKP are: >KPKP (black captures one white pawn) >KPPK (white captures the black pawn) >KQPKP (white promotes to a queen) >KRPKP (white promotes to a rook) >KBPKP (white promotes to a bishop) >KNPKP (white promotes to a knight) >KPPKQ (black promotes to a queen) >KPPKR (black promotes to a rook) >KPPKB (black promotes to a bishop) >KPPKN (black promotes to a knight) > And each one of these has its own sons, which must be calculated first, until >you reach KK, KBK or KNK (which are drawn). So, your storage requirements might >be a little higher. > With so many pawns, a tablebase with little information (like the one you want >to make), could be useful, as you can search only the branches which do not >decrease the exact score for the side to move. I think that practically you can do some assumptions to decrease the number of endings. for example KQPKP if white to move and the black only P is not close to be a queen is a win for white. white promotes only to a queen and not to a rook,bishop or knight practically the cases when white is winning this endgame by underpromotion are very rare. Uri
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