Scorpio

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Scorpio, a sophisticated open source chess engine by Daniel Shawul, written in C++ and compliant to the Chess Engine Communication Protocol with builds running under Windows and Linux. Scorpio participated at the CCT9, CCT11 and CCT12 online tournaments, and played the ICT 2007 over the board. It is base of Daniel's general game playing engine Nebiyu, able to play Chess variants, Checkers, Reversi, Go and Amazons.

=Description=

Board Representation
Scorpio combines Bitboards with a 0x88 board representation, and the coordinate transformation in scanning bits along with the lookup of the De Bruijn multiplication. The "unique" 64-bit routine was generated with the help of the De Bruijn Sequence Generator passing Daniel's birth date. Magic bitboard implementation by Pradu Kannan. Thanks for the acknowledgment of both!

Distributed Search
Scorpio performs a distributed search around an iterative depth-first search framework : Scorpio uses a decentralized approach (p2p) where neither memory nor jobs are centralized. Each host could have multiple processors in which case shared memory search (centralized search with threads) will be used. One processor per node will be started by mpirun, then each process at each node will create enough threads to engage all its processors.

MCTS
Scorpio 2.7.9, released in December 2017, optionally features a Monte-Carlo Tree Search (MCTS). Scorpio 2.8 in February 2018, MCTS with alpha-beta rollouts as suggested Bojun Huang. The parallel search for MCTS uses virtual loss to distribute work among threads in standard MCTS rollouts, and ABDADA like BUSY flag for alpha-beta rollouts. ABDADA and parallel MCTS from the Go world are very similar in nature.

Evaluation
Scorpio's evaluation includes following features and techniques :
 * NNUE (3.0.9)
 * Candidate Passed Pawn
 * Evaluation Hash Table
 * King Safety
 * Lazy Evaluation
 * Material
 * Mobility of bishops and knights
 * Outposts
 * Passed Pawn
 * Pawn Hash Table
 * Pawn Structure
 * Piece-Square Tables
 * Rook on Open File
 * Rook on Seventh
 * Tapered Eval
 * Trapped Pieces

Bitbases
see main article Scorpio Bitbases

Scorpio has its own endgame bitbase format, which might be probed by other programs via a shared library egbbdll.

ScorpioNN
The neural network version of Scorpio 2.9.0 (2019) works using egbbdll shared library that provides neural network inference via TensorFlow and/or TensorRT backends.

ScorpioNNUE
With the the advent of NNUE and its huge success in Stockfish NNUE, CFish NNUE and other engines, Daniel Shawul added NNUE support à la CFish into his egbbdll probing library, and reported more than 400 Elo out of his implementation with a shared library with Scorpio 3.0.9.

=See also=
 * BBC NNUE
 * DanChess
 * Nebiyu

=Dedicated Namesake=
 * Novag Scorpio 68000 from Schachcomputer.info Wiki » Novag, David Kittinger

=Forum Posts=

2005 ...

 * Scorpio chess engine by Daniel Shawul by Dann Corbit, CCC, April 18, 2005
 * Scorpio chess engine by Daniel Shawul by Dann Corbit, Winboard Forum, April 19, 2005
 * Gauntlet Scorpio v1.0 - games - new entry! by Karl-Heinz Söntges, CCC, April 21, 2005
 * Gauntlet Scorpio v1.1 - games - replaced DanChess by Karl-Heinz Söntges, CCC, June 02, 2005
 * Scorpio 1.3 looks promising by Dann Corbit, CCC, June 29, 2005
 * Scorpio 1.5 is very strong! by Ómar Skúlason, CCC, August 22, 2005
 * Has anyone tried the Scorpio engine? by Lance Perkins, CCC, October 05, 2005
 * Standardgauntlet - Scorpio is fighting for a place in the sun ! by Karl-Heinz Söntges, CCC, February 26, 2006
 * Special Scorpio 1.91 build for Core2Duo/Quad/Xeon by Jim Ablett, CCC, July 21, 2007
 * Scorpio 2.0 Windows x64 build available by Jim Ablett, CCC, December 22, 2007
 * Scorpio 64 bit questions by Denis P. Mendoza, CCC, December 23, 2007
 * Interesting Scorpio design by Kerwin Medina, Winboard Forum, November 05, 2008 » Iterative Search
 * Scorpio 202 Under Linux Resolved by Joshua Shriver, CCC, October 03, 2008

2010 ...

 * asynchronous search by Daniel Shawul, CCC, April 6, 2010
 * Scorpio 2.6 JA available by Jim Ablett, CCC, June 25, 2010
 * Scorpio 2.7 Linux by Jon Dart, CCC, December 02, 2011
 * Scorpio Chess 2.7 by Jim Ablett is out by Norbert Raimund Leisner, CCC, January 24, 2012

2015 ...
2018 2019
 * scorpio can run on 8192 cores by Daniel Shawul, CCC, August 22, 2015
 * Scorpio 2.7.7 by Krzysztof Grzelak, CCC, March 21, 2016
 * Happy halloween - scorpio 2.7.8 by Daniel Shawul, CCC, October 31, 2017
 * Scorpio 2.7.9 by Daniel Shawul, CCC, December 16, 2017
 * Alpha-Beta as a rollouts algorithm by Daniel Shawul, CCC, January 25, 2018 » Alpha-Beta, MCαβ, Monte-Carlo Tree Search
 * Scorpio 2.8 by Daniel Shawul, CCC, February 10, 2018
 * comparing minimax and averaging MCTS with alphabeta rollouts by Daniel Shawul, CCC, March 20, 2018 » Monte-Carlo Tree Search
 * Instruction for running Scorpio with neural network on linux by Daniel Shawul, CCC, August 01, 2018 » Neural Networks
 * Multithreaded batching on GPU for montecarlo and also alpha-beta by Daniel Shawul, CCC, September 03, 2018
 * Scorpio 2.8.7 MCTS+NN windows version by Daniel Shawul, CCC, September 08, 2018
 * Scorpio 2.8.9 with TensorRT support by Daniel Shawul, CCC, October 07, 2018
 * How to get ScorpioNN to work? by Torsten Schoop, CCC, July 16, 2019
 * Scorpio 3.0 by Daniel Shawul, CCC, August 16, 2019
 * Scorpio 3.0.2 by Werner Schüle, CCC, October 06, 2019

2020 ...

 * Re: Hacking around CFish NNUE by Daniel Shawul, CCC, October 15, 2020
 * Re: How to scale stockfish NNUE score? by Daniel Shawul, CCC, October 17, 2020
 * NNUE scoring (egbb lib) by Desperado, CCC, May 19, 2021 » NNUE,Scorpio NNUE

=External Links=

Chess Engine

 * Scorpio Chess and Nebiyu Alien
 * dshawul/Scorpio · GitHub
 * GitHub - dshawul/egbbdll: Probing code for scorpio bitbases
 * GitHub - dshawul/nn-probe: Library for probing neural networks
 * GitHub - dshawul/nnue-probe: for probing NNUE
 * Engine: Scorpio from WBEC Ridderkerk
 * The chess games of Scorpio from chessgames.com

Misc

 * Scorpio (astrology) from Wikipedia
 * Scorpius from Wikipedia
 * Scorpion from Wikipedia
 * Scorpion (disambiguation) from Wikipedia
 * Arthur Jones - Scorpio (1969), YouTube Video
 * feat. Beb Guérin and Claude Delcloo

=References=

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