Isolated+Pawns+(Bitboards)

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 * Home * Board Representation * Bitboards * Pawn Pattern and Properties * Isolated Pawns**

An Isolated Pawn or **Isolani** has no friendly pawns on adjacent files.  =Isolani by Square= To determine whether a pawn is isolated, we simply lookup an array with neighboring file-masks. If the intersection of neighbored files with own pawns is empty, the pawn is isolated. This symmetrical property appears to be equal for white and black pawns. code format="cpp" if ( (arrNeighborFiles[sqOfWhitePawn] & pawnBB[white]) == 0 ) -> pawn is isolated code

code arrNeighborFiles[d*] . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . . . 1 . 1 . . . code The arrNeighborFiles might be condensed to eight bitboards only, instead of 64 - if we index by code format="cpp" file(sq) == sq & 7 code instead of square.  =Isolanis and Half-isolanis set-wise= Isolated pawns are the relative complement of pawns with the union of their own attack fills over the whole file. To keep disjoint pawns with no neighbor on either east or west adjacent files has the advantage of greater versatility. Isolanis are the intersection of them, half-isolanis the exclusive or: code format="cpp" U64 noNeighborOnEastFile (U64 pawns) { return pawns & ~westAttackFileFill(pawns); }

U64 noNeighborOnWestFile (U64 pawns) { return pawns & ~eastAttackFileFill(pawns); }

U64 isolanis(U64 pawns) { return noNeighborOnEastFile(pawns) & noNeighborOnWestFile(pawns); }

U64 halfIsolanis(U64 pawns) { return noNeighborOnEastFile(pawns) ^ noNeighborOnWestFile(pawns); } code  =Hanging pawns= Hanging pawns are a duo of open and half-isolated pawns. code format="cpp" U64 wHangingPawns(U64 wpawns, U64 bpawns) { return wOpenPawns(wpawns, bpawns) & halfIsolanis(wpawns) & duo(wpawns); } code =What links here?= include page="Isolated Pawns (Bitboards)" component="backlinks" limit="20"
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