Contents

REBEL (chess)

REBEL

Original author(s)	Ed Schröder
Initial release	1980
Stable release	16.3 / March 11, 2024; 4 months ago (2024-03-11)[1][2][3]
Type	Chess engine
License	GNU General Public License v3.0 (14 and after) proprietary commercial software (13 and before)
Website	rebel13.nl

This article is part of the series on
Chess programming
Board representations 0x88 Bitboards
Evaluation functions Deep neural networks (Transformers) Attention Efficiently updatable neural networks Handcrafted evaluation functions Piece-square tables Reinforcement learning Stochastic gradient descent Supervised learning Texel tuning Unsupervised learning
Graph and tree search algorithms Minimax Alpha-beta pruning Principal variation search Quiescence search Monte Carlo tree search
Chess computers Belle ChessMachine ChipTest Cray Blitz Deep Blue Deep Thought HiTech Hydra Mephisto Saitek
Chess engines AlphaZero Chess Tiger Crafty CuckooChess Deep Fritz Dragon by Komodo Chess Fairy-Max Fritz Fruit GNU Chess HIARCS Houdini Ikarus Junior KnightCap Komodo Leela Chess Zero MChess Pro Mittens MuZero Naum REBEL Rybka Shredder Sjeng SmarThink Stockfish Torch Turochamp Zappa
v t e

REBEL is a world champion chess program developed by Ed Schröder. Development of REBEL started in 1980 on a TRS-80, and it was ported many times to dedicated hardware and the fastest microprocessors of the day:

• 1980s – Running on a TRS-80, Apple II, and inside of Mephisto brand dedicated chess computers, it won the Dutch open computer chess championship four times.
• 1991 – Ported to the ARM ChessMachine and named Gideon, it won the World Microcomputer Chess Championship.
• 1992 – Gideon won the World Computer Chess Championship, the first time a microprocessor came ahead of a field of mainframes, supercomputers, and custom chess hardware.
• 1990s – REBEL was ported to MS-DOS and then Microsoft Windows and sold commercially
  • 1997 – REBEL won a match with GM Arthur Yusupov 10.5–6.5, the first successful challenge of a chess grandmaster by a commercial program.
  • 1998 – REBEL won a match with GM Viswanathan Anand 5–3 (but lost 0.5–1.5 in the standard time control section of the match). He was rated number two in the world at the time.
• 2004 – Ed Schröder retired, releasing the last version of REBEL as the freeware chess engine Pro Deo.
• 2022 - On January 12, 2022, Ed Schröder came out of retirement to release REBEL 14 as a free chess engine. It incorporates an efficiently updatable neural network in REBEL's evaluation function, along with a heavily modified version of Fruit's search.^[4][5]

• Fruit (software)

• "Ed's recollection of REBEL's history". Archived from the original on 6 November 2020.
• "Wealth of information on the inner workings of a professional program". Archived from the original on 26 April 2011.
• Schröder, Ed. "How REBEL Plays Chess" (PDF). Archived from the original (PDF) on 6 November 2020.
• Rebel (Chess Programming Wiki)