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Sjaak ^[1],
an open source engine under the GNU General Public Licence written in C by Evert Glebbeek as younger sibling of Jazz, but able to play chess variants on various board sizes compliant to the Chess Engine Communication Protocol. Sjaak was first released in January 2011, not to confused with Ronald de Man's older private engine with the same name ^{[2] [3]}. The further extended SjaakII, released in early 2015, supports even more variants and protocols , and runs best under XBoard/WinBoard, version 4.8 (or better) ^[4] .

Variants

• Amazon Chess, where the queen moves as an amazon (needs to be played as variant "fairy" in XBoard).
• Berolina Chess, where pawns move one square diagonal and capture straight ahead.
• Burmese Chess, working but not tested fully.
• Capablanca Chess, a variant played on a 10x8 board with two extra pieces.
• Capablanca Random Chess
• Chess960 (Fischer Random Chess)
• Chinese Chess
• Courier Chess, a medieval variant played on a 12x8 board.
• Crazyhouse
• Gothic Chess, the same as Capablanca Chess but with a different starting position.
• Grand Chess, on a 10x10 board.
  Indian Grand Chess, or possibly Turkish Grand Chess. On a 10x10 with four extra pieces.
• Knightmate, where the king moves as a knight and the knights move as a king.
• Makruk, the Thai version of Chess.
• Normal chess
• Pocket Knight, like normal chess, but players have an extra knight they can drop on the board.
• Shatranj, a historic precursor of modern chess.
• Shogi ^[5]
• Spartan Chess, where black and white play with different armies and black has two kings
• The Maharaja and the Sepoys, where white has only one piece (the Maharaja) (needs to be played as variant "fairy" in XBoard).

Description

Board Representation

Despite boards exceeding 64 squares, like 10x8, 12x8, and 10x10, Sjaak is a native bitboard engine, utilizing either GCC's __int128 ^[6] extenstion on 64-bit platforms such as x86-64 or 128 bit vectors of integers on 32-bit platforms, the latter supporting SSE2 if available. Sjaak applies Kindergarten Bitboards to determine sliding piece attacks ^[7].

Search

Sjaak uses a fail-soft alpha-beta principal variation search with quiescence, null move pruning, late move reductions and check extensions inside an iterative deepening framework with transposition table ^[8]. Move ordering considers the killer, countermove and history heuristics. A modified version of a SEE routine from Jazz is used to evaluate captures .

Evaluation

Sjaak's static evaluation takes material balance, static piece-square tables derived from heuristics based on how pieces move, mobility and king safety into account, the latter only in chess variants with one king per side ^[9].

Namesake

• Sjaak (TrojanKnight) by Ronald de Man

See also

• Given Name
• Jazz
• Leonidas
• Sjakk

Forum Posts

2010 ...

• New Spartan-Chess engine: Sjaak by Harm Geert Muller, CCC, January 20, 2011
• Sjaak 263 by Evert Glebbeek, CCC, October 31, 2011
• Xiangqi chase algorithm by Evert Glebbeek, CCC, November 16, 2011 » Chinese Chess
• Sjaak 342 - new variants by Evert Glebbeek, CCC, November 16, 2011
• Sjaak 437 by Evert Glebbeek, CCC, December 11, 2011
• Sjaak 468 JA available by Jim Ablett, CCC, January 23, 2012
• Sjaak updated (revision 506) by Evert Glebbeek, CCC, February 01, 2013
• Shogi by Evert Glebbeek, CCC, October 20, 2014 » Shogi
• Xiangqi chase - again by Evert Glebbeek, CCC, November 06, 2014 » Chinese Chess
• Sjaak II - beta release! by Evert Glebbeek, CCC, November 19, 2014

2015 ...

• SjaakII 1.0 RC1 by Evert Glebbeek, CCC, January 29, 2015
• SjaakII 1.0.0 by Evert Glebbeek, CCC, March 18, 2015

2016

• SjaakII 1.2 RC1 by Evert Glebbeek, CCC, January 02, 2016
  SjaakII 1.2.0 is out! by Evert Glebbeek, CCC, January 08, 2016
  SjaakII 1.2.1 is out! by Evert Glebbeek, CCC, January 10, 2016
• Sjaak II question by Harm Geert Muller CCC, March 16, 2016
• SjaakII 1.3.0 (the happy easter edition) by Evert Glebbeek, CCC, March 26, 2016
• Question about Sjaak by Michel Van den Bergh, CCC, April 01, 2016
• Sjaak II, Wa Shogi and XBoard 4.9 by Harm Geert Muller, CCC, April 25, 2016 » Shogi, XBoard
• SjaakII 1.3.1 by Evert Glebbeek, CCC, July 05, 2016
• SjaakII 1.4.0 by Evert Glebbeek, CCC, November 27, 2016
• Sjaak II 1.4.1 and Shogi by Harm Geert Muller, CCC, December 14, 2016 » Shogi

2017

• I hate this hobby... by Evert Glebbeek, CCC, January 20, 2017 » Shogi

External Links

Chess Engine

• Chess (Jazz & Sjaak) home
• Chess (Jazz & Sjaak) downloads
• Sjaak 399 in CCRL 40/4

Misc

• Sjaak from Wikipedia
• Sjaak from Wikipedia.nl (Dutch)
• Willem Breuker, Pierre Courbois, Victor Kaihatu - Wonderful Girl of 17 Springs (1966), YouTube Video
  

References

1. ^ Sjaak - Dutch given name derived from Jacob, pronunciation similar to Schaak
2. ^ ICGA: Losing Chess by Guy Haworth
3. ^ Re: New Spartan-Chess engine: Sjaak by Vladimir Xern, CCC, January 21, 2011
4. ^ SjaakII 1.0.0 by Evert Glebbeek, CCC, March 18, 2015
5. ^ Shogi by Evert Glebbeek, CCC, October 20, 2014
6. ^ __int128 - Using the GNU Compiler Collection (GCC)
7. ^ Chess (Jazz & Sjaak) design
8. ^ Chess (Jazz & Sjaak) search
9. ^ Chess (Jazz & Sjaak) evaluation

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