Wing

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Forces acting on a wing

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 .

Description

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

• Material Balance
• Piece-Square Tables
• Development
• Mobility
• Pawn Structure

Backward Pawn

Doubled Pawn

Isolated Pawn

Passed Pawn

Connected Passed Pawns

• Pawn Hash Table
• Bishop Pair
• Rook on Open File
• King Safety in Opening, Middlegame

Pawn Shield

King Tropism

• 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 CCRL 40/4
• Download List from Ron Murawski's Computer-Chess Wiki
• Index of /chess/engines/Jim Ablett/WING by Jim Ablett, hosted by Kirill Kryukov

Chess

• Wing Gambit from Wikipedia

Misc

• Wing from Wikipedia
• Wing (disambiguation) from Wikipedia
• Wing (building) from Wikipedia
• Focus - Angle Wings, Live at Old Grey Whistle Test 1976, YouTube Video

Line-up: Thijs van Leer, Philip Catherine, Bert Ruiter, David Kemper

References

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