Author: Sune Fischer
Date: 05:25:03 03/05/03
Go up one level in this thread
On March 05, 2003 at 07:37:26, Georg v. Zimmermann wrote: >On March 04, 2003 at 07:12:21, Sune Fischer wrote: > >>On March 04, 2003 at 05:45:53, Georg v. Zimmermann wrote: >> >>>>While on the subject, how does one detect singular moves? >>>> >>>>-S. >>> >>>Shallower search for all possible moves on that node (Overhead). If all but 1 >>>move fall under a certain thereshold, that 1 is singular. >>> >>>Georg >> >>I just don't see how that works with alpha-beta. Is it a low-level minimax? >> >>-S. > >Why not ? Maybe I am missing smth. > >After you get the best move or fail high at a node you search all other moves >with a lower depth and a window at beta- margin (like 1.2 pawns). >If none of those searches fail high, they are all worse than the found move => >you research the best move with depth+singular_extension. > >The only situation where this fails is when you failed high on (i.e.) the 2nd >best move and during the depth-reduced search find the "real best move", which >of course fails high. Now you skip the singular extension even if the real best >move was actually singular, because it is much better than the first best move >found. But that case can be ignored since in such a situation the side to move >is already doing so well (2 ways to fail high, 1 of them even much better) it is >probably not a relevant node. I don't see any reason to extend a move I fail high on, unless there is a threat further down. In that case I would prefer a heuristic that extends on threats directly. Extending singular moves like PxQ where there is no threat involved is a waste of time as far as I can tell. But thanks for your technical explanation :) -S. >Georg
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