Re: [computer-go] RE: Scalability

[Don Dailey <drd@xxxxxxx>]

You are right of course.  The 1 ply extend idea of mine doesn't really capture
the spirit of quiescence.

- Don


   > -----Original Message-----
   > From: Don Dailey [mailto:drd@xxxxxxxxxxxxxxxxx]


   > From your email, it occured to me that YOUR quiecence search could
   > simply be:  Add 1 ply to the leaf if the move resulting in the leaf
   > position increased the score by some margin.

   This is almost the same as a 2-ply search with iterative deepening, if I
   understand you correctly. After the first 1-ply a program would try to
   search as many moves as possible to two ply, using a move order based on
   the score from the 1st ply search. "Highest score first" would of course
   include all moves larger than the margin proposed.

   By using the same local move heuristics for move ordering at the second
   ply, then most moves would be refuted immediately. But every time there
   is no beta cut all the legal moves will be searched, assuming normal
   alfa beta.

   Right now my program searches at most about 2-3 N moves (N = number of
   legal moves, (and many moves are never searched)). But if a better move
   than alfa is found 6 times then there will be more than 6N evaluations.

   But the worst problem is what to do with all moves at the second ply
   that is also "disturbing"? The same simple solution cannot be used
   recursively for infinity.

   Restraining the 2nd ply to only local responses is therefore perhaps the
   simplest and most effective solution (but in principle to restrictive
   since a reply to a forcing move is often a forcing move itself).
   Especially for my program where not even a 1-ply search is feasible late
   in the middlegame. It will sometimes barely search 20 moves (but up to
   10 moves 2ply locally for both colors) in positions with 150 legal
   moves.

   Only playing local moves then becomes analogical to exchanges in chess
   where the disturbing material simply is captured. In go, the aji of
   shape defects disappears when many stones are played in a local
   exchange.

   Interesting discussion! I do not think my way of doing is the best. I
   think it is too restrictive. It cannot handle situations where the best
   response is non-local. Because by "local" my program only count the
   moves very close the last played stone. The proper way of thinking about
   locality is at the group level and in the cases of semeais this is all
   weak groups recursively adjacent to the group under attack... which in
   the worst case is almost every legal move on the board...

   Regards
   Magnus
   --
   Magnus Persson
   Center for Adaptive Behavior and Cognition
   Tel: +49-(30)-82406-350
   Cell phone: +49 163 6639868

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