Author: Bas Hamstra
Date: 17:31:46 12/23/02
Go up one level in this thread
On December 23, 2002 at 19:33:50, Bas Hamstra wrote:
>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.
- - - - - - - -
- - B B B B - -
- - - - - - - -
- - - W W - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
Are these 2 white backward pawns? Neither can advance, neither be defended.
- - - - - - - -
- - - B - - - -
- - - - - - - -
- - - - W - - -
- - - - B - - -
- - - - - - - -
- - - W - - - -
- - - - - - - -
How many backward white pawns?
- - - - - - - -
- - - B - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
- - - - W - - -
- - - - - - - -
Is this a backward white pawn? Can backward pawns ueberhaupt be isolated?
I have had this more often. I keep seeing complications and eventually I don't
even know what a backward pawn actually is and therefore chose a trivial
definition. In books you typically see only this.
- - - - - - - -
- - - - - - B -
- - - - - B - -
- - - W - - - -
- - - - W - - -
- - - - - - - -
- - - - - - - -
- - - - - - - -
Best regards,
Bas.
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