Andscacs

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Andscacs, an UCI compliant chess engine by Daniel José Queraltó. Its development started in September 2013, and the first release was published in February 2014. Andscacs soon evolved to a top engine, becoming runner-up at the IGWT III losing the final from Chiron with the narrowest margin of 4½ - 5½, but taking revenge one year later at the IGWT IV, this time with 6½ - 5½ to its favour. At the Tenth Annual ACCA World Computer Rapid Chess Championship 2016, Andscacs emphasized its ambitions, and  became runner-up without losing a single game, but 12 wins and 3 draws, and thus the only program preventing later winner Komodo from a 100% score.

=Description= Being a bitboard engine, Andscacs determines sliding piece attacks ray-wise, quite similar to the classical approach. Since version 0.70, Andscacs uses magic bitboards to speed the attack calculations.

Search
Andscacs applies a principal variation search with tranposition table inside an iterative deepening framework with aspiration windows. Beside quiescence, selectivity is due to adaptive null move pruning, late move reductions, check extensions, singular extensions, razoring and futility pruning. Move ordering is further improved by the killer heuristic, IID and static exchange evaluation, the latter also used to prune bad captures in quiescence and futile moves near the horizon. Since version 0.70, a hash move is tried in quiescence search even if it’s a quiet move. Trying only captures and promotions was clearly weaker. Version 0.80 in Apil 2015 introduced a threaded parallel search, a Lazy SMP approach.

Evaluation
The evaluation considers material imbalances, and has piece-square tables for middlegame and endgame, piece values adapted by type of positions (open, closed), different types of piece mobility, king safety and sophisticated pawn structure evaluation with focus on passed pawns, most features smoothed out between game phases by a tapered eval. Since version 0.62u, evaluation scores are cached with a small evaluation hash table.

Tuning
The about 200 evaluation features were tuned with 750.000 positions to minimize the standard deviation of Stockfish's and Andscacs' static evaluation, which initially added a nice Elo boost to Andscacs, without playing too similar.

=Forum Posts=

2014

 * New engine - Andscacs by Daniel José Queraltó, CCC, February 06, 2014
 * Andscacs - New version by Daniel José Queraltó, CCC, February 09, 2014
 * Andscacs - New version by Daniel José Queraltó, CCC, March 03, 2014
 * Andscacs - New version 0.62w by Daniel José Queraltó, CCC, April 10, 2014
 * Andscacs - New version 0.62x by Daniel José Queraltó, CCC, May 05, 2014
 * Andscacs - New version 0.64 by Daniel José Queraltó, CCC, June 07, 2014
 * Andscacs - New version 0.70 by Daniel José Queraltó, CCC, November 05, 2014
 * Changes in Andscacs 0.70 by Daniel José Queraltó, CCC, November 08, 2014
 * Andscacs - New version 0.71 by Daniel José Queraltó, CCC, December 17, 2014
 * Changes in Andscacs 0.71 by Daniel José Queraltó, CCC, December 19, 2014

2015

 * Andscacs - New version 0.72 by Daniel José Queraltó, CCC, February 01, 2015
 * Andscacs - Test version 74024 by Daniel José Queraltó, CCC, April 09, 2015
 * Trying to improve lazy smp by Daniel José Queraltó, CCC, April 11, 2015 » Lazy SMP
 * Empirical results with Lazy SMP, YBWC, DTS by Kai Laskos, CCC, April 16, 2015 » Lazy SMP, YBWC, DTS
 * Andscacs - New version 0.80 by Daniel José Queraltó, CCC, April 17, 2015
 * Andscacs - New version 0.81 by Daniel José Queraltó, CCC, June 20, 2015
 * Andscacs - New version 0.81 - Detailed changes by Daniel José Queraltó, CCC, June 20, 2015


 * Andscacs - New version 0.82 by Daniel José Queraltó, CCC, August 16, 2015
 * Andscacs - New version 0.83 by Daniel José Queraltó, CCC, November 10, 2015
 * Andscacs - New version 0.84 by Daniel José Queraltó, CCC, December 07, 2015
 * Re: Why computing K that minimizes the sigmoid func. value? by Daniel José Queraltó, CCC, December 07, 2015 » Texel's Tuning Method

2016

 * Andscacs - New version 0.85 by Daniel José Queraltó, CCC, January 22, 2016
 * Andscacs - New version 0.86 by Daniel José Queraltó, CCC, March 24, 2016
 * Singular extension by Daniel José Queraltó, CCC, June 11, 2016 » Singular Extensions
 * Andscacs 0.86.196 BMI2 is available ... by Frank Quisinsky, June 15, 2016 » BMI2
 * Andscacs - New version 0.87 by Daniel José Queraltó, CCC, June 19, 2016
 * Andscacs - New version 0.872 by Daniel José Queraltó, CCC, July 23, 2016
 * Detailed changes in Andscacs from 0.86 to 0.872 by Daniel José Queraltó, CCC, July 25, 2016
 * Andscacs, developing version by Daniel José Queraltó, CCC, October 22, 2016
 * Andscacs - New version 0.88 by Daniel José Queraltó, CCC, October 28, 2016

2017

 * Andscacs - New version 0.90 by Daniel José Queraltó, CCC, March 25, 2017
 * Andscacs - New version 0.91 by Daniel José Queraltó, CCC, May 09, 2017
 * Andscacs new PH feature: first impressions by Rodolfo Leoni, CCC, July 08, 2017 » Persistent Hash Table
 * Andscacs - New version 0.92 by Daniel José Queraltó, CCC, September 17, 2017
 * Andscacs - New version 0.921 with source by Daniel José Queraltó, CCC, November 04, 2017
 * Re: Andscacs - New version 0.921 with source by Jon Dart, CCC, November 09, 2017 » TCEC Season 10
 * Re: Andscacs - New version 0.921 with source by Ronald de Man, CCC, November 11, 2017


 * Andscacs delta += delta / 3 + 4 by Alvaro Cardoso, CCC, December 27, 2017
 * Andscacs, test version by Daniel José Queraltó, CCC, December 31, 2017

2018

 * Andscacs - New version 0.93 by Daniel José Queraltó, CCC, January 14, 2018
 * Andscacs - New version 0.94 by Daniel José Queraltó, CCC, July 11, 2018
 * Andscacs - New version 0.95 by Daniel José Queraltó, CCC, December 17, 2018

2020

 * Andscacs by menniepals, CCC, February 14, 2020
 * Re: Andscacs by Daniel José Queraltó, CCC, February 15, 2020


 * Andscacs (34 versions) available ... by Frank Quisinsky, CCC, August 13, 2020

2021

 * Andscacs nnue 0.1 by Daniel José Queraltó, CCC, January 17, 2021 » NNUE

=External Links=

Chess Engine

 * Andscacs Homepage (Wayback Machine)
 * Andscacs in CCRL 40/40

Misc

 * Jorge Retamoza Cuarteto - La Cachila, Andorra Jazz Hivern Fest 2013, YouTube Video
 * Claudio Constantini, Alejandro Di Costanzo, Hernán Hock, Jorge Retamoza

=References= Up one level