Author: Omid David Tabibi
Date: 04:35:28 08/24/03
Go up one level in this thread
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. > >> 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? >The number of rooks is not needed afaik. > >>>Their directions and/or squares would be more valuable information I thought, so >>>that was what I went for. >>> >>>The real trick is probably to somehow make due without all this :) >>> >>>> >>>>> >>>>>I'm not really sure it is that great an idea, probably it is better to stick to >>>>>just using bitboards with squares. The index layer is not really needed as far >>>>>as I can tell. >>>> >>>>That is what I thought; if you are using 1 bit per piece, then why not just use >>>>bitboards... >>> >>>Because it's twice the space and takes longer to undo when you copy. >> >>Yes, these are the two things I hate about bitboards: the costly copy, and far >>more importantly, the annoying popcount for extracting the most simple >>information. > >I think re-shuffling a piece list at every capture is not so pretty either :) > >-S. >>>-S.
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