Author: Robert Hyatt
Date: 10:34:48 01/25/99
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On January 25, 1999 at 12:22:25, KarinsDad wrote: >On January 24, 1999 at 16:42:03, Robert Hyatt wrote: > >[snip] > >> >>>Is it OK to start probing the table at the first ply beyond the root? >> >>yes, because you now have a move played at the root.. and you can play that >>if the EXACT score comes up at ply=2 > >This confuses me (probably since I'm still new to this). > >This implies that you do not clear out your hash table immediately after the >program makes a move (i.e. during your opponent's time). For example: > Correct... I only clear it (and then only the score part) if something changes so drastically at the root that I alter my piece/square tables. One example is that after castling, my pawn advance stuff is modified, now that I know where the king is going to 'live'. >D E F G > \ / \ / > B C > \ / > A > >If you make move B, my thought was to remove all nodes C, F, and G assuming no >transpositions there. If a transposition was found, the count of times found >would just be decremented. > >If you do clear out the hash, then you should not be able to find a >transposition until ply 4 (i.e. e4 e5 is the same as e3 e6, e4 e5). The >transposition was not found until a ply 4 search (not a ply 2, that's just the >first time it was found). > >So if you do clear out the hash, then transpositions could not be found until >ply 4. If you do not clear out the hash, then transpositions could be found at >ply 1. The strange thing to me here is that if you do not clear out the hash, >you may find a few transpositions at ply 1 (from 3 ply moves ago), but it would >seem that this is not worth the effort since you would be saving information in >your table that is at least 3 ply old (and mostly next to worthless). > >I suddenly realized that maybe the phrase "root" meant not the original >position, but any position passed to the search algorithm. If so, disregard my >ramblings above. > 'root' is the initial position... from this position you have to find a move to play... which is why I don't probe at ply=1, because I need to search each move to find which is best, not find that they all fail low or whatever... But it is a moot point.. probing won't hurt just so you know how to handle the case where you reach search at ply=1 with alpha and beta set, you do a probe and get a value < alpha, or > beta before you search anything... >KarinsDad > >[snip]
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