Author: Robert Hyatt
Date: 21:22:30 12/23/02
Go up one level in this thread
On December 23, 2002 at 23:14:45, Miguel A. Ballicora wrote:
>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!
I would count _both_ as "weak" which is the super-class that contains
backward as well. The e pawn for white is just as bad as if it fit the
classic definition of backward. It isn't defended by a pawn. It can't
be defended by a pawn. It can't advance without being lost.
>
>>- - - - - - - -
>>- - - 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.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.