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[[FILE:IrvingAmenChessboard.jpg|border|right|thumb|link=http://www.irvingamen.com/works/Chessboard.htm|[[Arts#:Category:Irving Amen|Irving Amen]], - Chess Board <ref>[http://www.irvingamen.com/woodcutChess.htm Woodcuts with a Chess Theme] by [[Arts#:Category:Irving Amen|Irving Amen]]</ref> ]]

a set-wise representation with one bit for each [[Pieces|piece]] inside a one [[Double Word|32-bit word]]or two [[Word|16-bit words]] for each side. Piece-sets have some similarities with [[Bitboards|bitboards]], but each set bit does not directly associate a [[Squares|square]], but an index inside a [[Piece-Lists|piece-list]]. Thus to get the square, one additional indirection is necessary. Often the bit-position of a piece-set directly implies the information, what type and color the piece is - while bitboards usually maintains distinct sets for different pieces. That has advantages for instance in [[Static Exchange Evaluation|static exchange evaluation]], if one maintains an [[Attack and Defend Maps|attack-set]] as [[Incremental Updates|incremental updated]] [[Array|array]] or 64 piece-sets for each square.