Orion

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Orion Constellation ¹

Orion,
an UCI compliant chess engine by David Carteau, written in C and first released in May 2014. In August 2020, David Carteau published results using an own AVX2 NNUE implementation, initially compatible with Stockfish NNUE nets, with a huge improvement in playing strength ¹. He has designed and trained his own NNUE-like approach published as Cerebrum open source library on GitHub ², first used within Orion 0.8, released in December 2020 ³.

Features

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Board Representation

• Bitboards
• Plain Magic Bitboards
• BMI2 - PEXT Bitboards

Search

• Lazy SMP (0.9)
• Iterative Deepening
• Aspiration Windows
• Alpha-Beta
• Principal Variation Search
• Transposition Table
• Selectivity
  • Adaptive Null Move Pruning
  • Static Null Move Pruning
  • Late Move Reductions
  • Futility Pruning
  • Razoring
  • Quiescence Search
  • Delta Pruning
  • SEE Pruning
• Move Ordering
  • Hash Move, even Quiet Moves in Quiescence
  • Static Exchange Evaluation
  • History Heuristic

Evaluation

• NNUE (0.7.nnue)
• NNUE-like Cerebrum (0.8)
• Automated Tuning by Linear Regression using Python scikit-learn (0.6) ⁵
• Automated Tuning by PBIL (pre 0.6)
• Pawn Structure
  • Isolated Pawns etc ...
  • Passed Pawns
• Mobility
• Square Control
• Space
• King Safety
• Attacking King Zone

Misc

• Syzygy Bases (removed in 0.8)

Forum Posts

2014 ...

• New free engine - Orion by Graham Banks, CCC, May 24, 2014
• New Orion release : v0.3 ! by David Carteau, CCC, April 03, 2016
• New Orion release : v0.4 ! by David Carteau, CCC, October 15, 2017
• New Orion release : v0.5 ! by David Carteau, CCC, June 21, 2018
• New Orion release : v0.6 ! by David Carteau, CCC, June 01, 2019

2020 ...

• Orion 0.7 release by David Carteau, CCC, July 04, 2020
• Orion 0.7 : NNUE experiment by David Carteau, CCC, August 19, 2020
• Re: You've trained a brilliant NN(UE) King-Piece Network. Now what? by David Carteau, CCC, November 19, 2020 » NNUE
• Orion 0.8 + The Cerebrum release by David Carteau, CCC, December 01, 2020
• Orion 0.9 release by David Carteau, CCC, April 12, 2022

External Links

Chess Engine

• Orion UCI chess engine
• GitHub - david-carteau/cerebrum: The Cerebrum library
• Orion (Schachprogramm) – Wikipedia.de (German)
• Orion in CCRL Blitz

Misc

• Orion from Wikipedia
• Orion (mythology) from Wikipedia
• Orion (constellation) from Wikipedia
• Orion (comics) from Wikipedia
• Orion (sculpture) from Wikipedia » University of Michigan
• Steps Ahead - Orion, Yin-Yang (1992), YouTube Video

lineup: Mike Mainieri, Steve Smith, Jeff Andrews, Bendik Hofseth, Rachel Z

Watch on YouTube

References