Author: Robert Hyatt
Date: 08:08:48 01/13/05
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On January 13, 2005 at 05:36:41, Tony Werten wrote: >Hi all, > > >when checking my own tables, I found out that the following (illegal ) position, >causes the Nalimov code( rather, the decompresssion code ) disabled further egtb >probes. > >No problem for normal use, just when you're doing something without checking if >the position is legal, it goes wrong. > >The position looks like it might have been optimized away, causing a probe >beyond the uncompressed size of the filechunck just read in, causing an >"invalid" flag on the tablebase, resulting in a disabling of the KNNkp >tablebase. > >[D]4K3/8/8/k7/8/1N6/p7/N7 w - - 0 0 > >Tony I believe this has always been a restriction. Since one way to compress the database (before the raw compression algorithm) is to weed out positions that are not possible, such as two kings on adjancent squares, both kings in check, pawns on illegal squares, etc. I suppose the probe code could be modified to do all the legality checks, but then it would have to be able to generate moves to see if a king is in check and the other side is on move, etc. It makes more sense for the chess engine to do that stuff since it knows about legality issues anyway... Perhaps Eugene will comment further...
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