Bad Bishop

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Bad bishop, a bishop whose mobility is restricted by own pawns. As opposed to normal mobility problems, this situation is semi-permanent (more so if the position is blocked), which fact justifies singling it out as another evaluation term. Bad bishop is not such a liability if it is placed outside the pawn chain (Bf5 in the Slav). For that reason some programs, like Crafty, score a bishop as bad only if its forward mobility is impaired.

For a bitboard-based program a feasible approach would be to create an array of 64 bitboards, indexed by a Bishop's position, and marking the pawn positions which would make our bishop bad.

=See also=
 * Pawn Rams (Bitboards)
 * Bishops of Opposite Colors
 * Color of a Square
 * Color Weakness

=Publications=
 * Matej Guid, Martin Možina, Jana Krivec, Aleksander Sadikov, Ivan Bratko (2008). Learning Positional Features for Annotating Chess Games: A Case Study. CG 2008, pdf

=Forum Posts=
 * Evaluating bad bishops by Tord Romstad, Winboard Programming Forum, May 15, 2006
 * Bad/good bishops in R3 and IPPOLIT/IvanHoe by Mark Watkins, Open Chess Programming Forum, November 30, 2010

=External Links=
 * Good bishop and bad bishop from Wikipedia
 * How Bad is a Bad Bishop? by Iryna Zenyuk, Chess.com, February 27, 2019
 * The Bishow's Show: Bad Bishop by Iryna Zenyuk, Chess.com, March 09, 2012

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