Author: Sune Fischer
Date: 07:06:47 06/15/03
Go up one level in this thread
On June 15, 2003 at 09:06:50, Bo Persson wrote: >On June 15, 2003 at 04:48:58, Sune Fischer wrote: > >>On June 14, 2003 at 23:57:41, Russell Reagan wrote: >> >>>On June 14, 2003 at 19:34:12, Magoo wrote: >>> >>>>"Maybe it is possible not to check for check at all and just check if a capture >>>>removes the king one ply later." >>>> >>>>Yes this is possible, but as i discoverd its really slow, in the early stages of >>>>my program i did just what you say. The thing is if you are going to do a search >>>>to depth D, you are really doing a search to depth D+1, which is much much >>>>slower than doing a search to depth D and calling in_check() after each move. >>> >>>I think if you use the "capture the king" method of detecting illegal moves, you >>>have to sort the move list first, and put "captures of the king" at the very >>>top. Then if your program moves a piece that was pinned (exposing the king, >>>illegal), the very first next move you will search will be the capture of the >>>king. So you only visit one extra node, not one extra ply. If you don't sort the >>>illegal moves to the top of your legal move list, then you will do a LOT of >>>searching before you find the illegal move, and your program will probably be >>>slow. >> >>Actually you don't need to make any of the moves or even sort the list to see if >>the king is captured. You can start by scanning the movelist for a king capture. > >And if you already have a MVV/LVA routine, it will pop up there automatically if >you just score it higher than PxQ. > > >>The problem is that you generated moves in a illegal position (because your last >>move was illegal), and that is just pure no good for nothing overhead. > >Except if it is faster than *always* verifiying the legality first. :-) > >The extra move generation (captures only?) will happen just sometimes, the >legality check will be needed for every move. Which is fastest? Yes, I mentioned that somewhere. It is about the frequency of illegal moves versus the cost. The thing that makes really makes it worth it IMO, is if you make a special check evade generator. -S.
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