Wing

a WinBoard compliant chess engine by Stef Luijten written in C++, first released in October 2004. Initially influenced by Crafty, Wing was released as open source in December 2010 to demonstrate the basics of chess programming , shortly before Stef Luijten started his Winglet tutorial //Writing a Chess Program in 99 Steps//. || toc =Description=
 * Home * Engines * Wing**
 * [[image:320px-Lift-force-en.svg.png link="http://commons.wikimedia.org/wiki/File:Lift-force-en.svg"]] ||~ || **Wing**,
 * Forces acting on a wing ||~ ||^ ||

Board Representation
Wing is a bitboard engine and determines sliding piece attacks using rotated bitboards. The inner six bits optimization yields to four lookup tables of 64x64x8 bytes, that is 32-KiB each or 1/8 MiB in total for ranks, files, diagonals and anti-diagonals. Interestingly, this attack table layout was preserved in Winglet, when line-wise occupied states were rotated on the fly by magic multiplication and shift right.

Search
Wing performs a negamax alpha-beta search with conditional compiled (default on) PVS inside the iterative deepening framework without aspiration windows. The recent version has a always replace transposition table using Zobrist keys, while earlier versions used an additional depth-preferred replacement table. As stated by its author in 2006, Wing has gained over 100 ELO points from adding history pruning, while the published sources lack LMR.

Selectivity

 * Check Extensions
 * Null Move Pruning
 * Quiescence Search
 * Recapture Extensions
 * Passed Pawn Extensions
 * Threat Extensions
 * Futility Pruning
 * Extended Futility Pruning
 * Razoring

Move Ordering

 * Principal Variation Extraction from TT
 * Killer Heuristic
 * History Heuristic
 * MVV-LVA

Evaluation
> Backward Pawn > Doubled Pawn > Isolated Pawn > Passed Pawn > Connected Passed Pawns > Pawn Shield > King Tropism
 * Material Balance
 * Piece-Square Tables
 * Development
 * Mobility
 * Pawn Structure
 * Pawn Hash Table
 * Bishop Pair
 * Rook on Open File
 * King Safety in Opening, Middlegame
 * King Centralization in Endgame

=See also=
 * Crafty
 * Little Wing
 * Winglet

=Forum Posts=
 * [|Wing exit from Winboard!] by Pablo, Winboard Forum, October 25, 2004
 * [|wing engine files] by Adam Wilks, CCC], November 01, 2005
 * [|Hash table hit rate] by Stef Luijten, Winboard Forum, November 16, 2005 » Transposition Table
 * [|Re: history pruning/ late move pruning] by Stef Luijten, Winboard Forum, March 02, 2006

=External Links=

Chess Engine

 * [|Wing] from WBEC Ridderkerk
 * [|Index of /chess/engines/Jim Ablett/WING] by Jim Ablett, hosted by Kirill Kryukov

Chess

 * [|Wing Gambit from Wikipedia]

Misc
> Line-up: [|Thijs van Leer], Philip Catherine, [|Bert Ruiter], [|David Kemper] > media type="youtube" key="12L57vsovEc" width="560"
 * [|Wing from Wikipedia]
 * [|Wing (disambiguation) from Wikipedia]
 * [|Wing (building) from Wikipedia]
 * Focus - [|Angle Wings], Live at [|Old Grey Whistle Test] 1976, [|YouTube] Video

=References= =What links here?= include page="Wing" component="backlinks" limit="40"
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