Author: Robert Hyatt
Date: 08:31:06 01/21/00
Go up one level in this thread
On January 21, 2000 at 11:23:19, José Carlos wrote: > Averno has a very slow move generation. Although I know I have to face this >problem soon, I'd like to try some methods to avoid the horizont effect, that >causes me lots of headaches. > How did old machines (Forte/Super Forte, Mephisto Almeria/Portorose, etc...) >that ran in very slow hardware avoid this problem? > I don't think null move can help me, since my prog sees 4-6 plys in midgame, >so I can't apply null move at so shallow depth (am I wrong about this?). I >implemeted hash tables, that improves move ordering, but hash tables are not >magic. > About extensions, I implemented checks and recaptures, but since my prog had >problems in long series of captures, I define recapture as a capture after >another, not necessaryly reestablishing the material imbalance. As well, I >extend a full ply in recaptures, since in a so shallow depth, it is very >difficult to find four captures (most people extend 3/4 ply in recaptures, >right?). > Extensions help, but I still got problems with horizont effect. > > Any suggestions? > > Thanks in advance. > > José C. > >PS.: I use PVS and Aspiration search. The solution to the horizon effect is depth. And extensions. The most common horizon effect type of move is a check, which constrains the opponent to react to the check, and removes 2 plies from the depth. Extend on the check and you cut the loss by 1 ply. A capture/recapture is the next most likely cause, as a capture must either be followed by the recapture, a different capture to maintain material balance, or a check. Again you lose 2 plies. And extending on a capture/recapture pair will recover one of those plies. The capture, check, get out of check, recapture group of moves is harder of course...
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