Author: Bas Hamstra
Date: 16:33:50 12/23/02
Go up one level in this thread
On December 23, 2002 at 19:07:51, Gerd Isenberg wrote:
>On December 23, 2002 at 16:13:21, Bas Hamstra wrote:
>
>>Gerd,
>>
>>Those fill routines are really neat. I have a few tiny enhancements and am
>>working on more. How about this:
>>
>>// determine where white pawns can go safely, with a floodfill up:
>>WSafePath = FFillUp(WPawns, ~(AllPawns|BDominated) );
>>
>>// now we can calc "pawn-defendable" more accurately:
>>WDefendable = ((WPawnAttacksRight >> 16) & WSafePath) << 7 |
>> ((WPawnAttacksLeft >> 16) & WSafePath) << 9 ;
>>
>>// to be used in backward pawns:
>>WBackWard = ((~AllPawns & BDominated) >> 8) & WPawns & ~WDefendable;
>>
>>Best regards,
>>Bas.
>
>Hi Bas,
>
>Wow, absolutely great!!!
>Pawn-defendable is really more accurate.
>
>I guess FFillUp(g, p) is Steffan's FillUpOccluded and WPawns are therefore
>member of WSafePath.
Yes, that is 100% correct. I played with this routines to check the speed of the
non-mmx versions, but it seems then I have a "wrap-around" problem?
>BitBoard FFillUp(BitBoard g, BitBoard p)
>{
> g |= p & (g << 8);
> p &= (p << 8);
> g |= p & (g << 16);
> p &= (p << 16);
> return g | (p & (g << 32));
>}
>
>What do you think about (2.rank) pawns thay may push safely one step foreward,
>but became backward afterwards?
Yes, I have been thinking about this too, but it gave me a headache :-) Because,
what to say about pawns that become backward if 3 squares advanced? What is the
definition of backward pawn, in fact? Is a pawn on the third rank counted as
backward if it would be backward if 2 squares advanced?
WELL??
:-)
Best regards,
Bas.
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