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'''[[Main Page|Home]] * [[Board Representation]] * [[Bitboards]] * [[Pawn Pattern and Properties]] * Open Pawns'''
'''Open Pawns''' have no mechanical obstruction - an opponent pawn in front. They are at least half-free or even free [[Passed Pawn|passers]]. Thus, open pawns are a superset of passed pawns and half-free pawns like [[Candidate Passed Pawn|candidates]] but also weak pawns like the half-free [[Backward Pawns (Bitboards)#Straggler|straggler]] ([[Backward Pawn|backward pawn]] ) or half-free [[Isolated Pawn|isolanis]]. Open pawns are vulnerable from opponent rook-attacks on [[Half-open file|half-open files]].
=Open Single Pawn=
Working in the ''square centric'' world of the board, thus using a square index of '''one''' particular pawn, likely from [[Bitboard Serialization|bitboard traversal]], to lookup pre-calculated pattern.
For a single pawn we need to access a lookup-table to get all squares on the same file in front of the pawn. If the intersection of the fronspan with the set of opponent pawns is empty, it is a open pawn.
<pre>
U64 arrFrontSpans[2][64];
if ( (arrFrontSpans[white][sqOfWhitePawn] & pawnBB[black]) == 0 ) -> pawn open
</pre>
<pre>
arrFrontSpan[white][d4]
. . . 1 . . . .
. . . 1 . . . .
. . . 1 . . . .
. . . 1 . . . .
. . . p . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
</pre>
<span id="OpenPawnsSetwise"></span>
=Open Pawns set-wise=
Working in the ''bitboard centric'' world to determine pawn related pattern ''set-wise''.
Open Pawns have no mechanical obstruction in front - an opponent pawn as member of the own [[Pawn Fills|frontfill]] or [[Pawn Spans|frontspan]]. A relative complement with the opponents frontspans is sufficient to determine open pawns:
<pre>
U64 wOpenPawns(U64 wpawns, U64 bpawns) {
return wpawns & ~bFrontSpan(bpawns);
}
U64 bOpenPawns(U64 bpawns, U64 wpawns) {
return bpawns & ~wFrontSpan(wpawns);
}
</pre>
=See also=
* [[Candidates (Bitboards)|Candidates]]
* [[Passed Pawns (Bitboards)|Passed Pawns]]
* [[Backward Pawns (Bitboards)#Straggler|Straggler]]
* [[Unfree Pawns (Bitboards)|Unfree Pawns]]
'''[[Pawn Pattern and Properties|Up one Level]]'''
'''Open Pawns''' have no mechanical obstruction - an opponent pawn in front. They are at least half-free or even free [[Passed Pawn|passers]]. Thus, open pawns are a superset of passed pawns and half-free pawns like [[Candidate Passed Pawn|candidates]] but also weak pawns like the half-free [[Backward Pawns (Bitboards)#Straggler|straggler]] ([[Backward Pawn|backward pawn]] ) or half-free [[Isolated Pawn|isolanis]]. Open pawns are vulnerable from opponent rook-attacks on [[Half-open file|half-open files]].
=Open Single Pawn=
Working in the ''square centric'' world of the board, thus using a square index of '''one''' particular pawn, likely from [[Bitboard Serialization|bitboard traversal]], to lookup pre-calculated pattern.
For a single pawn we need to access a lookup-table to get all squares on the same file in front of the pawn. If the intersection of the fronspan with the set of opponent pawns is empty, it is a open pawn.
<pre>
U64 arrFrontSpans[2][64];
if ( (arrFrontSpans[white][sqOfWhitePawn] & pawnBB[black]) == 0 ) -> pawn open
</pre>
<pre>
arrFrontSpan[white][d4]
. . . 1 . . . .
. . . 1 . . . .
. . . 1 . . . .
. . . 1 . . . .
. . . p . . . .
. . . . . . . .
. . . . . . . .
. . . . . . . .
</pre>
<span id="OpenPawnsSetwise"></span>
=Open Pawns set-wise=
Working in the ''bitboard centric'' world to determine pawn related pattern ''set-wise''.
Open Pawns have no mechanical obstruction in front - an opponent pawn as member of the own [[Pawn Fills|frontfill]] or [[Pawn Spans|frontspan]]. A relative complement with the opponents frontspans is sufficient to determine open pawns:
<pre>
U64 wOpenPawns(U64 wpawns, U64 bpawns) {
return wpawns & ~bFrontSpan(bpawns);
}
U64 bOpenPawns(U64 bpawns, U64 wpawns) {
return bpawns & ~wFrontSpan(wpawns);
}
</pre>
=See also=
* [[Candidates (Bitboards)|Candidates]]
* [[Passed Pawns (Bitboards)|Passed Pawns]]
* [[Backward Pawns (Bitboards)#Straggler|Straggler]]
* [[Unfree Pawns (Bitboards)|Unfree Pawns]]
'''[[Pawn Pattern and Properties|Up one Level]]'''
