Orion

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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. He has designed and trained his own NNUE-like approach published as Cerebrum open source library on GitHub, first used within Orion 0.8, released in December 2020.

=Features=

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)
 * 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

=References= Up one level