Author: Gerd Isenberg
Date: 15:57:20 12/17/02
Go up one level in this thread
<snip>
>>Hi Uri,
>>
>>OK you have pawnBB[2] with white pawns pawnBB[WHITE] and black pawns
>>pawnBB[BLACK]. "allPawns" combines both sets by or.
>>
>>Some pawn-patterns on the fly (I'm at work and can't look to my sources):
>>
>
>Thanks for the information
>
>I thoughtabout your post and understood part of it.
>Here are my comments when I tried to explain it to myself.
>At this moment I did not understand what is the meaning of duo
>and there were some other things that I did not understand.
OK, i made some mistakes on the fly and try to correct or comment.
Some of the terms are german introduced by the austrian Chess Master H.Kmoch in
"Die Kunst der Bauernführung".
Widder, Hebel and Duo:
[D] 8/6pp/8/1p2p3/1P1P4/6PP/8/8 w - -
>
>>pawnAttacksAH[WHITE] = (pawnBB[WHITE] << 9) & 0xfefefefefefefefe;
>
>
>for me a1=0... h1=7 a2=8...h8=63
Yes.
pawnAttacksAH[WHITE] = (pawnBB[WHITE] << 9) & NOTFILEABB;
... all white pawn attacks from a to h direction. Due to wrap around of pawns
from h to a-file by shift up (<<8) and left (<<1, means board right here from
whites point of view!) it is necessary to clear these possible wrapped bits by
anding with a not a-file bitboard.
With mmx-registers anding with NOTFILEABB is not necessary due to bytewise
(rankwise) add (paddb mm1,mm1) instead of shift left one.
>
>suppose we are in the opening position
>I guess pawnBB[WHITE]=(1<<8)+(1<<9)+...(1<<15)
>
>pawnsBB[white]<<9=(1<<17)+(1<<18)+...(1<<24)
>0xfefefefefefefefe helps to get rid of the 1<<24 because fe mean 1 only at files
>b-h
>>pawnAttacksHA[WHITE] = (pawnBB[WHITE] << 7) & 0x7f7f7f7f7f7f7f7f;
>
>here we need to get rid of h4 that is not attacked
>
>7f is 1 in files a-g so it help for this target.
>
>>pawnAttacks[WHITE] = pawnAttacksAH[WHITE] | pawnAttacksHA[WHITE];
>>pawnDblAttacks[WHITE] = pawnAttacksAH[WHITE] & pawnAttacksHA[WHITE];
>
>understood
>
>squares that are attacked by 1 pawn and squares that are attacked by 2 pawns.
>
>>
>>hebel[WHITE] = pawnAttacks[WHITE] & pawnBB[BLACK];
>
>black pawns that are attacked by white pawns.
Yes, but my definition was wrong. That are the black "hebel"-pawns.
hebel[WHITE] = pawnBB[WHITE] & pawnAttacks[BLACK];
hebel[BLACK] = pawnBB[BLACK] & pawnAttacks[WHITE];
>
>>widder[WHITE] = (pawnBB[WHITE] << 8) & pawnBB[BLACK]
>
>
>If I understand correctly blocked white pawns by black pawns with distance of
>one square.
Yes, i also changed colors here
widder[WHITE] = pawnBB[WHITE] & (pawnBB[BLACK] >> 8);
widder[BLACK] = pawnBB[BLACK] & (pawnBB[WHITE] << 8);
>
>> /* & ~hebel[WHITE] */;
>>defended[WHITE] = pawnAttacks[WHITE] & pawnBB[WHITE];
>
>understood.
>>duo[WHITE] = ((pawnBB[WHITE]<<8)& pawnAttacks[WHITE]
>> & ~pawnDblAttacks[WHITE]) >> 8;
>
>What does it mean?
Duos are two pawns of same color on neighboared files and same rank.
A duo-pawn is a pawn whose advance square is controlled exactly by one (but not
two) neighboared pawn.
>>
>>Some helpfull routines:
>>
>>BitBoard fillUp(BitBoard bb)
>>{
>> bb |= (bb<<8);
>> bb |= (bb<<16);
>> bb |= (bb<<32);
>> return bb;
>>}
>>
>>BitBoard fillDown(BitBoard bb)
>>{
>> bb |= (bb>>8);
>> bb |= (bb>>16);
>> bb |= (bb>>32);
>> return bb;
>>}
Kogge-Stone generator routines introduced by Steffan Westcott.
I give two epd-strings representing the source bb and the return bitboard for
fillUp:
[D] 8/8/8/1P6/4PP2/8/7P/8 w - -
[D] 1Q2QQ1Q/1Q2QQ1Q/1Q2QQ1Q/1P2QQ1Q/4PP1Q/7Q/7P/8 w - -
>
>I guess that fillup(pawnBB[WHITE]) gives me all the squares that white pawn can
>visit without captures by pawns
>I will say later in this post that these are the squares that the white pawns
>"see" when filldown(pawnBB[BLACK]) are the square that black pawns "see"
>correct?
>
>
<snip>
>I do not understand why white pawns cannot be in these files.
>
>Uri
OK, forgot the last errornous routines, this should be better and easier:
openPawns[WHITE] = pawnBB[WHITE] & ~filldown(allPawns);
passedPawns[WHITE] = pawnBB[WHITE] & ~filldown(allPawns|pawnAttacks[BLACK]);
notDefendable[WHITE] = pawnBB[WHITE] & fillup(pawnAttacks[WHITE]);
OpenPawns: All pawns without own or opposite pawns infront on same file.
Backward pawns:
First we need all squares dominated by sides pawn attacks:
pawnDomination[side] = (pawnDblAttacks[side] & ~pawnDblAttacks[other(side)])
| (pawnAttacks[side] & ~pawnAttacks[other(side)]);
backWard1[WHITE] = notDefendable[WHITE] & (pawnDomination[BLACK] >> 8);
backWard2[WHITE] = backWard1[WHITE] & openPawns[WHITE];
I hope this helps a bit and gives you an impression of the compution of
pawn-bitboard pattern. Your questions 4) affects more singular properties of a
pawn.
But even here Kogge-Stone-Up/Down fill (the passers as generator g, own attacks
as propagator p) may be helpfull to get a set of the closest possible defenders
(for each passer simultaniously).
Steffan Westcott's routines for this purpose:
BitBoard FillUpOccluded(BitBoard g, BitBoard p)
{
g |= p & (g << 8);
p &= (p << 8);
g |= p & (g << 16);
p &= (p << 16);
return g |= p & (g << 32);
}
BitBoard FillDownOccluded(BitBoard g, BitBoard p)
{
g |= p & (g >> 8);
p &= (p >> 8);
g |= p & (g >> 16);
p &= (p >> 16);
return g |= p & (g >> 32);
}
Question 5 is a bit unclear to me, i guess you mean candidates?
May you post some sample epd-strings?
Gerd
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