Author: Sune Fischer
Date: 04:57:07 08/24/03
Go up one level in this thread
On August 24, 2003 at 07:35:28, Omid David Tabibi wrote: >On August 24, 2003 at 07:19:55, Sune Fischer wrote: > >>On August 24, 2003 at 06:41:28, Omid David Tabibi wrote: >> >>>On August 23, 2003 at 20:53:40, Sune Fischer wrote: >>> >>>>On August 23, 2003 at 20:28:02, Omid David Tabibi wrote: >>>> >>>>>How do you find out how many pieces of a kind attack a square? E.g., how do you >>>>>calculate the number of rooks that attack a square? >>>> >>>>If you just want the number this is not the fastest, you need to popcount. >>>>However, I don't really see what good such a number would be. >>> >>>If you want to update your table dynamically, you need to know how many pieces >>>of a kind attack a certain square. >> >>You don't need the number as such, what you need to know is exactly who does the >>attacking, cause those are the ones that needs to be updated. >>Howelse do you do *incremental* update? > >I know how many pieces of a kind attack each square. So, when for example I move >a piece out of e4 and find out that e4 is attacked by one rook, I check to find >out which rook was the attacker. Yes and it is _this_ check that you save with the table, it's a lookup. >> >>> E.g., you move a piece out of e4, and you >>>know that e4 is attacked by rook. Rook is a sliding piece and know that attack >>>table should be updated. If you don't know by _how many_ rooks is e4 attacked, >>>then you have to check all your rooks to check whether they attack e4. If you >>>exactly know the number of attacking rooks however, you can stop as soon as you >>>find the appropriate number. >> >>So lets say there are 2 rooks attacking e4, then what? >>Where are these two rooks and how does this move change their attack status. > >What about 2 queens attacking e4? Huh? Same problem, every sliding attacker to that square needs to be updated (with a few exceptions). -S.
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