Wing

Forces acting on a wing 1 Forces acting on a wing ¹

Forces acting on a wing, thrust, lift, drag, and weight, Image by Bartosz Kosiorek, Bird flight from Wikipedia, Wikimedia Commons ↩︎

Wing,
a WinBoard compliant chess engine by Stef Luijten written in C++, first released in October 2004. Initially influenced by Crafty ¹, Wing was released as open source in December 2010 to demonstrate the basics of chess programming ², shortly before Stef Luijten started his Winglet tutorial Writing a Chess Program in 99 Steps ³.

Contents

Description
See also
Forum Posts
External Links
1. Chess Engine
2. Chess
3. Misc
References

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 ⁴. As stated by its author in 2006, Wing has gained over 100 ELO points from adding history pruning ⁵, while the published sources lack LMR.