Author: David Eppstein
Date: 15:46:36 10/09/98
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On October 09, 1998 at 15:24:26, Robert Hyatt wrote: >This doesn't matter however, because *every* possible position must be accounted >for, with an exact distance to mate for the side on move with that specific >piece configuration. So they *all* have to be computed to build the next one >after them... You don't need distance to mate if you are searching from a non-tablebase position trying to reach a tablebase position (and aren't worried about the 50 move rule, but you must not be since you're using distance to mate). If the actual game reaches a won tablebase position, you need some way to force progress, but it doesn't have to be distance to mate. If you can always search deeply enough to find a conversion (capture or pawn move), you can use distance to conversion, and only store win/loss/draw in the tablebase. In any KXP-KP or KX-KPP endgame, searching deeply enough to find a conversion should be easy (there are fewer than a million distinct positions in which at most one pawn has moved, so you can load just that part of the tablebase into memory and use the hashtable to do the search quickly no matter how deep it is). But I agree with your main point, that the heuristics suggested by the poster you were responding to aren't good enough -- the information needs to be exact, and you need to compute lots of other tablebases before you can think about KPP-KP.
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