Author: Guido
Date: 06:35:58 08/30/99
I downloaded the Nalimov's tablebases generator (ftp://ftp.cis.uab.edu/pub/hyatt/TB/tbgen.zip) and tried to compile and execute, that happened without problems under an old Linux version (Slackware 1.2.13), installed on an Intel P133. By the way I observe that compiling with gcc option -fomit-frame-pointer saves about 10% in execution time since this option adds an extra register for local (register) variables. As I wrote a similar program that generates tablebases, I was interested in comparing results. Analyzing randomly single positions I found coincident answers in terms of number of moves to mate or to lose, but statistics differ between tbgen and my program, except for kpk and kppk endings. For all the other endings I obtain the same maximum number of moves for victory or defeat, but the number of positions, won or lost, versus number of moves, are a little different, always with larger values for tbgen in respect to my program, and therefore the total number of valid positions (no. bytes of the file - broken positions?) differs too. I suppose that my program should be wrong in analyzing symmetry or checks, eliminating positions that should have been considered. Now I would like to find the error and therefore I ask if somebody can kindly help me. I found the simplest example of inconsistency in the file kqkn.tbs where I notice that White moves and wins in 21 moves in 4 positions, while my program indicates that such positions, keeping into account symmetry, are only 3, and exactly: 1. White: Ka1, Qb1 Black: Kc3, Nc2 White moves 2. White: Kb1, Qb2 Black: Kd3, Nc3 White moves 3. White: Kd1, Qe2 Black: Kc3, Nb2 White moves I checked these positions successfully with the command tbgen -q, but I don't know how to find the missing one, without trying more than one million positions. Does a program exist to extract positions with the same result from Nalimov's tablebases? Knowing the fourth position I hope to have a good hint to detect the error. Thanks in advance Guido
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