Author: Bruce Moreland
Date: 23:02:28 06/25/02
Go up one level in this thread
On June 25, 2002 at 05:26:34, Sune Fischer wrote:
>On June 24, 2002 at 20:33:32, Russell Reagan wrote:
>
>>I am not an experienced bitboard user. I've been thinking about trying them out
>>just to see how they work in comparison with my current 0x88 implementation. Is
>>there any potential problem in mixing the two approaches? One problem that I can
>>see would be that if you have an index for a bitboard, it's not going to index
>>into the same square in your 0x88 array. I suppose the only real reason to keep
>>0x88 would be for efficient edge detection. Do bitboards offer a solution to
>>edge detection? Or do they even need edge detection when using bitboards (ex.
>>using the BSF asm instuction would seem to avoid edge detection altogheter)?
>>
>>Thanks,
>>Russell
>
>For edge detection you can do this:
>
>if (((uint64)1<<square)&0xFF818181818181FF)
> ...
>
>it will tell you when you are on the first and last file or rank.
>I use that in my SEE to raytrace behind the attacking piece, something like
>
>while (!(((uint64)1<<square)&0xFF818181818181FF)) {
> square+=direction;
> if (there-is-an-attacker-on-square)
> add-it-to-the-list-of-attackers
>}
>
That shift has to be lots of fun for the processor.
bruce
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