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. Scorpio 2.7.9, released in December 2017, optionally features a Monte-Carlo Tree Search.

=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 2.8, released in February 2018 optionally provides a Monte-Carlo Tree Search using 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 :
 * 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.

=See also=
 * Arthropod
 * Astronomy
 * DanChess
 * Mythology

=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
 * 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 ...

 * 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

=External Links=

Chess Engine

 * Scorpio Chess and Nebiyu Alien
 * dshawul/Scorpio · GitHub
 * Engine: Scorpio from WBEC Ridderkerk
 * Update: scorpio 2.5 debian package (unofficial), Linux and Chess, March 13, 2010
 * The chess games of Scorpio from chessgames.com

Misc

 * Scorpio (astrology) from Wikipedia
 * Scorpius from Wikipedia
 * Scorpion from Wikipedia
 * Scorpion (disambiguation) from Wikipedia

=References=

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