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[[FILE:L'Ange du Foyeur.jpg|border|right|thumb|link=https://www.chessprogramming.org/File:L%27Ange_du_Foyeur.jpg|[[Arts#:Category:Max Ernst|Max Ernst]] - L'Ange du Foyer, 1937 <ref>[https://en.wikipedia.org/wiki/Max_Ernst Max Ernst from Wikipedia]</ref> ]]

determines whether a [[Squares|square]] is [[Attacks|attacked ]] and/or defended by various or specific [[Pieces|pieces]]. So far, as elaborated in [[Pawn Pattern and Properties|pawn]]-, [[Knight Pattern|knight]]- and [[King Pattern|king pattern]], as well as [[Sliding Piece Attacks|sliding piece attacks]], we are able to generate all attacks and target-sets of all pieces, sufficient to [[Move Generation|generate]] all [[Pseudo-Legal Move|pseudo legal moves]]. It is often useful to generate [[Attacks|attacks]] '''to''' a certain square, or to look whether [[Moves|moves]] retrieved elsewhere are pseudo legal or [[Legal Move|legal]]. Some programs maintain [[Incremental Updates|incremental updated]] [[Attack and Defend Maps|attack tables]] for that purpose. The techniques proposed on this page are intended to use on the fly.

A branch-less solution without any lookups and some parallel gain is likely too expensive on the fly and may at most used for initialization purposes<ref>[http://www.talkchess.com/forum3/viewtopic.php?f=7&t=12499&start=14 Re: Check idea + bittwiddler request] by [[Gerd Isenberg]], [[CCC]], April 06, 2007</ref>: