Author: Pat King
Date: 16:16:39 12/03/02
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On December 03, 2002 at 17:49:01, Robert Hyatt wrote: >On December 03, 2002 at 13:09:42, Pat King wrote: > >>On December 03, 2002 at 11:29:56, Robert Hyatt wrote: >> [snip] >>Perhaps there's a middle ground here. You can sort the scores of the fail-lows >>at the root, cost O(B^2) at worst, and then probe the hash table for the >>corresponding variations. You'd know the PV was worth (say) exactly 314, >>variation 1 < 271, variation 2 < 141, etc. As a practical matter, how useful are >>those less-than scores? >>[snip] >> >>Pat > > >How can you do that? You don't know _exact_ scores for the moves that failed >low. You >only know an upper bound on each, as the real scores for each of those moves >could be even >worse had the entire sub-tree been searched. > I understand that. I can see a user, however, being interested in knowing that what he views as the best move is at least (say) half a pawn worse, or that several moves may have scores nearly equal to the PV's. What could be the killer is thinking that sorting on those upper bounds means anything. >Fail-low scores don't contain any information that can be compared between them, So your position would be that sorting them, and presenting (say) the "top five", would be invalid. >all >they are useful for is to compare against the best move... and we already know >and have >proven they are worse, just not by how much. We've proven at LEAST how much. That could be useful while doing interactive analysis. What seems dodgy to me, perhaps, is assigning any merit to the resulting order.
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