Author: Miguel A. Ballicora
Date: 20:14:45 12/23/02
Go up one level in this thread
On December 23, 2002 at 20:31:46, Bas Hamstra wrote:
>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.
No.
>- - - - - - - -
>- - - B - - - -
>- - - - - - - -
>- - - - W - - -
>- - - - B - - -
>- - - - - - - -
>- - - W - - - -
>- - - - - - - -
>
>How many backward white pawns?
None!
>- - - - - - - -
>- - - B - - - -
>- - - - - - - -
>- - - - - - - -
>- - - - - - - -
>- - - - - - - -
>- - - - W - - -
>- - - - - - - -
>
>Is this a backward white pawn? Can backward pawns ueberhaupt be isolated?
No.
>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 - - -
>- - - - - - - -
>- - - - - - - -
>- - - - - - - -
e4 is a backward pawn. Backward pawn is a pawn
1) that is in an semi open column
2) that the next square is attacked by an opponent pawn.
3) that could be strong because it had the potential to be defended, since it
has a friendly pawn in a neighbor column, but the structure is not right to
happen with just simple pawn moves.
e4 not a backward pawn:
- - - - - - - -
- - - - - - B -
- - - - - B - -
- - - W - - - -
- - - - W - - -
- - - - - - - -
- - - - - W - -
e4 is a backward pawn:
- - - - - - - -
- - - - - - - -
- - - - - B - -
- - - W - - - -
- - - - W - - -
- - - - - B - -
- - - - - W - -
- - - - - - - -
e4 is a tough call, but generally it is not called in that way.
- - - - - - - -
- - - - - - - -
- - - - - B - -
- - - W - - - -
- - - - W - B -
- - - - - - - -
- - - - - W - -
- - - - - - - -
That is just semantics, but is what it has been generally understood.
Miguel
>
>
>
>Best regards,
>Bas.
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