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Created page with "'''Home * Chess * Squares * Occupancy''' FILE:ZappaBesetzt20160916.JPG|border|right|thumb|Occupied <ref>[https://de-de.facebook.com/umspannwerk.reckli..."
'''[[Main Page|Home]] * [[Chess]] * [[Squares]] * Occupancy'''
[[FILE:ZappaBesetzt20160916.JPG|border|right|thumb|Occupied <ref>[https://de-de.facebook.com/umspannwerk.recklinghausen/posts/10153757793891429 Besetzt!] (Occupied) - [https://en.wikipedia.org/wiki/Toilet Toilet] exhibition at [https://de.wikipedia.org/wiki/Umspannwerk_Recklinghausen Umspannwerk Recklinghausen], today [https://en.wikipedia.org/wiki/RWE RWE] [https://en.wikipedia.org/wiki/Technology_museum Technology museum] in [https://en.wikipedia.org/wiki/Recklinghausen Recklinghausen], Germany, and part of [[Arts#IndustrialHeritageTrail|The Industrial Heritage Trail]] of the [https://en.wikipedia.org/wiki/Ruhr Ruhr area] - [https://en.wikipedia.org/wiki/Toilet#Others Portable toilet] labeled Rock:Klo with [[Videos#FrankZappa|Frank Zappa]] [http://wiki.killuglyradio.com/wiki/The_Toilet_Poster Toilet Poster] inside, Photo by [[Gerd Isenberg]], September 16, 2016</ref> ]]
The '''Occupancy''' refers to the boolean property of a square. It is occupied if any [[Pieces|piece]] exclusively resides on that square, otherwise the square is empty. In [[Bitboards|bitboards]], the occupancy or ''occupied bitboard'' refers the set of all squares occupied by any piece. Thus, it is the [[General Setwise Operations#Union|union]] of all [[Bitboard Board-Definition|piece bitboards]], which is used for instance in calculating [[Sliding Piece Attacks|sliding piece attacks]]. Likely, while the piece bitboards are [[Incremental Updates|updated incrementally]], the occupancy is updated incrementally as well, rather than calculated from up to 12 piece bitboards each time.
Alternatively, if needed more often, the [[General Setwise Operations#ComplementSet|complement]] set of the occupancy, the set of '''all empty squares''' is exclusively kept inside the board-definition and a cheap not-instruction is done to calculate the occupancy on the fly. Other programs keep disjoint white and black pieces, to "or" them if the occupancy is actually needed. The appearance of multiple, redundant occupied bitboards, which are [[Flipping Mirroring and Rotating|flipped, mirrored or rotated]] are eponym of bitboard methods related to [[Sliding Piece Attacks|sliding piece attack generation]], most notably [[Rotated Bitboards|rotated]] and [[Reverse Bitboards|reverse bitboards]].
=See also=
* [[Sliding Piece Attacks]]
: [[Obstruction Difference]]
: [[Occupancy of any Line]]
: [[Reverse Bitboards]]
: [[Rotated Bitboards]]
=Forum Posts=
* [http://www.open-chess.org/viewtopic.php?f=5&t=2240 Occupancy Variations] by [[Christian Daley|CDaley11]], [[Computer Chess Forums|OpenChess Forum]], January 25, 2013 » [[Magic Bitboards]]
=External Links=
* [https://en.wikipedia.org/wiki/Occupancy Occupancy from Wikipedia]
* [https://en.wiktionary.org/wiki/occupancy occupancy - Wiktionary]
=References=
<references/>
'''[[Squares|Up one Level]]'''
[[FILE:ZappaBesetzt20160916.JPG|border|right|thumb|Occupied <ref>[https://de-de.facebook.com/umspannwerk.recklinghausen/posts/10153757793891429 Besetzt!] (Occupied) - [https://en.wikipedia.org/wiki/Toilet Toilet] exhibition at [https://de.wikipedia.org/wiki/Umspannwerk_Recklinghausen Umspannwerk Recklinghausen], today [https://en.wikipedia.org/wiki/RWE RWE] [https://en.wikipedia.org/wiki/Technology_museum Technology museum] in [https://en.wikipedia.org/wiki/Recklinghausen Recklinghausen], Germany, and part of [[Arts#IndustrialHeritageTrail|The Industrial Heritage Trail]] of the [https://en.wikipedia.org/wiki/Ruhr Ruhr area] - [https://en.wikipedia.org/wiki/Toilet#Others Portable toilet] labeled Rock:Klo with [[Videos#FrankZappa|Frank Zappa]] [http://wiki.killuglyradio.com/wiki/The_Toilet_Poster Toilet Poster] inside, Photo by [[Gerd Isenberg]], September 16, 2016</ref> ]]
The '''Occupancy''' refers to the boolean property of a square. It is occupied if any [[Pieces|piece]] exclusively resides on that square, otherwise the square is empty. In [[Bitboards|bitboards]], the occupancy or ''occupied bitboard'' refers the set of all squares occupied by any piece. Thus, it is the [[General Setwise Operations#Union|union]] of all [[Bitboard Board-Definition|piece bitboards]], which is used for instance in calculating [[Sliding Piece Attacks|sliding piece attacks]]. Likely, while the piece bitboards are [[Incremental Updates|updated incrementally]], the occupancy is updated incrementally as well, rather than calculated from up to 12 piece bitboards each time.
Alternatively, if needed more often, the [[General Setwise Operations#ComplementSet|complement]] set of the occupancy, the set of '''all empty squares''' is exclusively kept inside the board-definition and a cheap not-instruction is done to calculate the occupancy on the fly. Other programs keep disjoint white and black pieces, to "or" them if the occupancy is actually needed. The appearance of multiple, redundant occupied bitboards, which are [[Flipping Mirroring and Rotating|flipped, mirrored or rotated]] are eponym of bitboard methods related to [[Sliding Piece Attacks|sliding piece attack generation]], most notably [[Rotated Bitboards|rotated]] and [[Reverse Bitboards|reverse bitboards]].
=See also=
* [[Sliding Piece Attacks]]
: [[Obstruction Difference]]
: [[Occupancy of any Line]]
: [[Reverse Bitboards]]
: [[Rotated Bitboards]]
=Forum Posts=
* [http://www.open-chess.org/viewtopic.php?f=5&t=2240 Occupancy Variations] by [[Christian Daley|CDaley11]], [[Computer Chess Forums|OpenChess Forum]], January 25, 2013 » [[Magic Bitboards]]
=External Links=
* [https://en.wikipedia.org/wiki/Occupancy Occupancy from Wikipedia]
* [https://en.wiktionary.org/wiki/occupancy occupancy - Wiktionary]
=References=
<references/>
'''[[Squares|Up one Level]]'''
