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Created page with "'''Home * Board Representation * Bitboards * Sliding Piece Attacks * Rotated Indices''' FILE:Mittman_Yellow_Cherries.jpg|border|right|thumb|link=h..."
'''[[Main Page|Home]] * [[Board Representation]] * [[Bitboards]] * [[Sliding Piece Attacks]] * Rotated Indices'''
[[FILE:Mittman_Yellow_Cherries.jpg|border|right|thumb|link=http://www.barbaramittman.com/Site/Yellow_Cherries.html| [[Arts#Mittman|Barbara Mittman]], Yellow Cherries <ref>[http://www.barbaramittman.com/Site/Still_Lifes.html Still Lifes] by [[Arts#Mittman|Barbara Mittman]]</ref> ]]
'''Rotated indices''',<br/>
a deconcentrated version of [[Rotated Bitboards|rotated bitboards]], proposed by [[Alessandro Damiani]] <ref>[http://groups.google.com/group/rec.games.chess.computer/msg/5c1c40a08c7176f8 Re: Rotated bitboards] by [[Alessandro Damiani]], [[Computer Chess Forums|rgcc]], October 31, 1997</ref> as used in his engine [[Fortress (Engine)|Fortress]]. Instead of using rotated bitboards with packed 15 [[Diagonals|diagonals]] and 15 [[Anti-Diagonals|anti-diagonals]] each, Alessandro applies an [[Array|array]] of 16 + 30 rotated indices for all 16 orthogonal and 30 diagonal lines on the board. Those indices are [[Incremental Updates|incrementally updated]] during [[Make Move|make]]/[[Unmake Move|unmake]], which takes a tad more effort - but once updated, the rotated indices pay off, the more often they are used inside a [[Node|node]] of the [[Search|search]]. No further computation is required to look up attacks, pure indexed memory accesses.
The possible disadvantage - rotated indices, similar or slightly worse than rotated bitboards, are not as versatile as techniques relying on one occupancy bitboard only - if it is about a temporary change of the occupancy on the fly for [[X-ray Attacks (Bitboards)|x-rays]] and [[Pin|pinned pieces]] etc..
=See also=
* [[Flipping Mirroring and Rotating]]
* [[Fortress (Engine)|Fortress]]
* [[Rotated Bitboards]]
* [[Gk#SlidingAttacks|Rotated Indices in Gk]]
=Forum Posts=
* [http://groups.google.com/group/rec.games.chess.computer/msg/5c1c40a08c7176f8 Re: Rotated bitboards] by [[Alessandro Damiani]], [[Computer Chess Forums|rgcc]], October 31, 1997
* [https://www.stmintz.com/ccc/index.php?id=342812 Re: Resources about rotated bitboards] by [[Alessandro Damiani]], [[CCC]], January 16, 2004
=References=
<references />
'''[[Sliding Piece Attacks|Up one Level]]'''
[[Category:Barbara Mittman]]
[[FILE:Mittman_Yellow_Cherries.jpg|border|right|thumb|link=http://www.barbaramittman.com/Site/Yellow_Cherries.html| [[Arts#Mittman|Barbara Mittman]], Yellow Cherries <ref>[http://www.barbaramittman.com/Site/Still_Lifes.html Still Lifes] by [[Arts#Mittman|Barbara Mittman]]</ref> ]]
'''Rotated indices''',<br/>
a deconcentrated version of [[Rotated Bitboards|rotated bitboards]], proposed by [[Alessandro Damiani]] <ref>[http://groups.google.com/group/rec.games.chess.computer/msg/5c1c40a08c7176f8 Re: Rotated bitboards] by [[Alessandro Damiani]], [[Computer Chess Forums|rgcc]], October 31, 1997</ref> as used in his engine [[Fortress (Engine)|Fortress]]. Instead of using rotated bitboards with packed 15 [[Diagonals|diagonals]] and 15 [[Anti-Diagonals|anti-diagonals]] each, Alessandro applies an [[Array|array]] of 16 + 30 rotated indices for all 16 orthogonal and 30 diagonal lines on the board. Those indices are [[Incremental Updates|incrementally updated]] during [[Make Move|make]]/[[Unmake Move|unmake]], which takes a tad more effort - but once updated, the rotated indices pay off, the more often they are used inside a [[Node|node]] of the [[Search|search]]. No further computation is required to look up attacks, pure indexed memory accesses.
The possible disadvantage - rotated indices, similar or slightly worse than rotated bitboards, are not as versatile as techniques relying on one occupancy bitboard only - if it is about a temporary change of the occupancy on the fly for [[X-ray Attacks (Bitboards)|x-rays]] and [[Pin|pinned pieces]] etc..
=See also=
* [[Flipping Mirroring and Rotating]]
* [[Fortress (Engine)|Fortress]]
* [[Rotated Bitboards]]
* [[Gk#SlidingAttacks|Rotated Indices in Gk]]
=Forum Posts=
* [http://groups.google.com/group/rec.games.chess.computer/msg/5c1c40a08c7176f8 Re: Rotated bitboards] by [[Alessandro Damiani]], [[Computer Chess Forums|rgcc]], October 31, 1997
* [https://www.stmintz.com/ccc/index.php?id=342812 Re: Resources about rotated bitboards] by [[Alessandro Damiani]], [[CCC]], January 16, 2004
=References=
<references />
'''[[Sliding Piece Attacks|Up one Level]]'''
[[Category:Barbara Mittman]]
