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'''[[Main Page|Home]] * [[Engines]] * chess22k'''
'''chess22k''',<br/>
an [[UCI]] compliant [[:Category:Open Source|open source chess engine]] by [[Sander Maassen vd Brink]], written in [[Java]] first released in January 2017 <ref> [http://open-chess.org/viewtopic.php?t=3068 chess22k v1.0] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], January 13, 2017</ref>. While already in the 2400 Elo range using a 64-bit [https://en.wikipedia.org/wiki/Java_virtual_machine Java Runtime Environment (JRE)], it has not initially implemented a [[Tapered Eval|tapered evaluation]], but abrupt transition based on piece counts per side to distinguish between [[Middlegame|middlegame]] and [[Endgame|endgame]] terms <ref>public boolean isEndGame(int color) in [https://github.com/sandermvdb/chess22k/blob/master/src/main/java/nl/s22k/chess/ChessBoard.java chess22k/ChessBoard.java at master · sandermvdb/chess22k · GitHub]</ref> <ref>isEndGame used in [https://github.com/sandermvdb/chess22k/blob/master/src/main/java/nl/s22k/chess/eval/EvalUtil.java chess22k/EvalUtil.java at master · sandermvdb/chess22k · GitHub]</ref>. However, tapered evaluation was implemented in chess22k '''1.5''' along with new evaluation terms adjusted by [[Texel's Tuning Method|Texel's tuning method]] <ref>[http://www.talkchess.com/forum/viewtopic.php?t=64869 chess22k 1.5 released] by [[Sander Maassen vd Brink]], [[CCC]], August 12, 2017</ref>. In November 2017, chess22k had its over the board tournament debut, version '''1.6''' played the [[CSVN]] [[PT 52]] in Leiden, quite successful - shared 4th place with 6/9. Soon released afterwards, chess22k '''1.6''' requires [[Java#9|Java 9]] <ref>[http://www.talkchess.com/forum/viewtopic.php?t=65714 chess22k 1.6 released] by [[Sander Maassen vd Brink]], [[CCC]], November 13, 2017</ref>.
=Features=
<ref>Based on readme and [https://github.com/sandermvdb/chess22k GitHub - sandermvdb/chess22k]</ref>
==[[Board Representation]]==
* [[Bitboards]]
* [[Magic Bitboards]]
==[[Search]]==
* [[Lazy SMP]] (1.10)
* [[Iterative Deepening]]
* [[Aspiration Windows]]
* [[Principal Variation Search]]
* [[Transposition Table]]
* [[Move Ordering]]
** [[History Heuristic]]
** [[Internal Iterative Deepening]]
** [[Killer Heuristic]]
* [[Selectivity]]
** [[Null Move Pruning]]
** [[Late Move Reductions]]
** [[Razoring]]
** [[Futility Pruning]]
** [[Static Exchange Evaluation|SEE Pruning]]
==[[Evaluation]]==
* [[Evaluation Hash Table]]
* [[Tapered Eval]] 1.5
* [[Material]]
* [[Bishop Pair]]
* [[Piece-Square Tables]]
* [[Mobility]]
** [[Trapped Pieces]]
** [[Rook on Open File|Rooks on (Semi) Open Files]]
* [[Outposts]]
* [[Pawn Hash Table]]
* [[Pawn Structure]]
** [[Doubled Pawn]]
** [[Isolated Pawn]]
** [[Passed Pawn]]
* [[King Safety]]
** [[King Safety#PawnShield|Pawn Shelter]]
* [[Tactics|Tactical Penalties]]
** [[Check|In Check]]
** [[Hanging Piece|Hanging Pieces]]
** [[Pin|Pinnned Pieces]]
* [[Texel's Tuning Method]]
=Forum Posts=
==2017==
* [http://open-chess.org/viewtopic.php?t=3068 chess22k v1.0] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], January 13, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63118 New release: chess22k v1.1] by [[Sander Maassen vd Brink]], [[CCC]], February 09, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63496 chess22k 1.2 released] by [[Sander Maassen vd Brink]], [[CCC]], March 19, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63835 chess22k 1.3 released] by [[Sander Maassen vd Brink]], [[CCC]], April 26, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64189 Texel tuning method question] by [[Sander Maassen vd Brink]], [[CCC]], June 05, 2017 » [[Texel's Tuning Method]]
* [http://www.talkchess.com/forum/viewtopic.php?t=64310 Impressive Texel-tuning results] by [[Sander Maassen vd Brink]], [[CCC]], June 16, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64337 chess22k 1.4 released] by [[Sander Maassen vd Brink]], [[CCC]], June 18, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64869 chess22k 1.5 released] by [[Sander Maassen vd Brink]], [[CCC]], August 12, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=65714 chess22k 1.6 released] by [[Sander Maassen vd Brink]], [[CCC]], November 13, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=66171 chess22k 1.7 released] by [[Sander Maassen vd Brink]], December 28, 2017
==2018==
* [http://www.talkchess.com/forum/viewtopic.php?t=66282 chess22k progress overview] by [[Sander Maassen vd Brink]], January 09, 2018
* [http://www.talkchess.com/forum/viewtopic.php?t=66727 chess22k 1.8 released] by [[Sander Maassen vd Brink]], [[CCC]], March 04, 2018
* [http://www.talkchess.com/forum/viewtopic.php?t=67206 chess22k 1.9 released] by [[Sander Maassen vd Brink]], [[CCC]], April 23, 2018
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=67941 chess22k 1.10 released] by [[Sander Maassen vd Brink]], [[CCC]], July 09, 2018
=External Links=
* [https://github.com/sandermvdb/chess22k GitHub - sandermvdb/chess22k]
* [http://www.computerchess.org.uk/ccrl/404/cgi/engine_details.cgi?print=Details&eng=chess22k%201.4%2064-bit chess22k 1.4 64-bit] in [[CCRL|CCRL 40/4]]
=References=
<references />
'''[[Engines|Up one Level]]'''
[[Category:UCI]]
[[Category:Open Source]]
[[Category:Java]]
'''chess22k''',<br/>
an [[UCI]] compliant [[:Category:Open Source|open source chess engine]] by [[Sander Maassen vd Brink]], written in [[Java]] first released in January 2017 <ref> [http://open-chess.org/viewtopic.php?t=3068 chess22k v1.0] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], January 13, 2017</ref>. While already in the 2400 Elo range using a 64-bit [https://en.wikipedia.org/wiki/Java_virtual_machine Java Runtime Environment (JRE)], it has not initially implemented a [[Tapered Eval|tapered evaluation]], but abrupt transition based on piece counts per side to distinguish between [[Middlegame|middlegame]] and [[Endgame|endgame]] terms <ref>public boolean isEndGame(int color) in [https://github.com/sandermvdb/chess22k/blob/master/src/main/java/nl/s22k/chess/ChessBoard.java chess22k/ChessBoard.java at master · sandermvdb/chess22k · GitHub]</ref> <ref>isEndGame used in [https://github.com/sandermvdb/chess22k/blob/master/src/main/java/nl/s22k/chess/eval/EvalUtil.java chess22k/EvalUtil.java at master · sandermvdb/chess22k · GitHub]</ref>. However, tapered evaluation was implemented in chess22k '''1.5''' along with new evaluation terms adjusted by [[Texel's Tuning Method|Texel's tuning method]] <ref>[http://www.talkchess.com/forum/viewtopic.php?t=64869 chess22k 1.5 released] by [[Sander Maassen vd Brink]], [[CCC]], August 12, 2017</ref>. In November 2017, chess22k had its over the board tournament debut, version '''1.6''' played the [[CSVN]] [[PT 52]] in Leiden, quite successful - shared 4th place with 6/9. Soon released afterwards, chess22k '''1.6''' requires [[Java#9|Java 9]] <ref>[http://www.talkchess.com/forum/viewtopic.php?t=65714 chess22k 1.6 released] by [[Sander Maassen vd Brink]], [[CCC]], November 13, 2017</ref>.
=Features=
<ref>Based on readme and [https://github.com/sandermvdb/chess22k GitHub - sandermvdb/chess22k]</ref>
==[[Board Representation]]==
* [[Bitboards]]
* [[Magic Bitboards]]
==[[Search]]==
* [[Lazy SMP]] (1.10)
* [[Iterative Deepening]]
* [[Aspiration Windows]]
* [[Principal Variation Search]]
* [[Transposition Table]]
* [[Move Ordering]]
** [[History Heuristic]]
** [[Internal Iterative Deepening]]
** [[Killer Heuristic]]
* [[Selectivity]]
** [[Null Move Pruning]]
** [[Late Move Reductions]]
** [[Razoring]]
** [[Futility Pruning]]
** [[Static Exchange Evaluation|SEE Pruning]]
==[[Evaluation]]==
* [[Evaluation Hash Table]]
* [[Tapered Eval]] 1.5
* [[Material]]
* [[Bishop Pair]]
* [[Piece-Square Tables]]
* [[Mobility]]
** [[Trapped Pieces]]
** [[Rook on Open File|Rooks on (Semi) Open Files]]
* [[Outposts]]
* [[Pawn Hash Table]]
* [[Pawn Structure]]
** [[Doubled Pawn]]
** [[Isolated Pawn]]
** [[Passed Pawn]]
* [[King Safety]]
** [[King Safety#PawnShield|Pawn Shelter]]
* [[Tactics|Tactical Penalties]]
** [[Check|In Check]]
** [[Hanging Piece|Hanging Pieces]]
** [[Pin|Pinnned Pieces]]
* [[Texel's Tuning Method]]
=Forum Posts=
==2017==
* [http://open-chess.org/viewtopic.php?t=3068 chess22k v1.0] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], January 13, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63118 New release: chess22k v1.1] by [[Sander Maassen vd Brink]], [[CCC]], February 09, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63496 chess22k 1.2 released] by [[Sander Maassen vd Brink]], [[CCC]], March 19, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=63835 chess22k 1.3 released] by [[Sander Maassen vd Brink]], [[CCC]], April 26, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64189 Texel tuning method question] by [[Sander Maassen vd Brink]], [[CCC]], June 05, 2017 » [[Texel's Tuning Method]]
* [http://www.talkchess.com/forum/viewtopic.php?t=64310 Impressive Texel-tuning results] by [[Sander Maassen vd Brink]], [[CCC]], June 16, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64337 chess22k 1.4 released] by [[Sander Maassen vd Brink]], [[CCC]], June 18, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=64869 chess22k 1.5 released] by [[Sander Maassen vd Brink]], [[CCC]], August 12, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=65714 chess22k 1.6 released] by [[Sander Maassen vd Brink]], [[CCC]], November 13, 2017
* [http://www.talkchess.com/forum/viewtopic.php?t=66171 chess22k 1.7 released] by [[Sander Maassen vd Brink]], December 28, 2017
==2018==
* [http://www.talkchess.com/forum/viewtopic.php?t=66282 chess22k progress overview] by [[Sander Maassen vd Brink]], January 09, 2018
* [http://www.talkchess.com/forum/viewtopic.php?t=66727 chess22k 1.8 released] by [[Sander Maassen vd Brink]], [[CCC]], March 04, 2018
* [http://www.talkchess.com/forum/viewtopic.php?t=67206 chess22k 1.9 released] by [[Sander Maassen vd Brink]], [[CCC]], April 23, 2018
* [http://www.talkchess.com/forum3/viewtopic.php?f=2&t=67941 chess22k 1.10 released] by [[Sander Maassen vd Brink]], [[CCC]], July 09, 2018
=External Links=
* [https://github.com/sandermvdb/chess22k GitHub - sandermvdb/chess22k]
* [http://www.computerchess.org.uk/ccrl/404/cgi/engine_details.cgi?print=Details&eng=chess22k%201.4%2064-bit chess22k 1.4 64-bit] in [[CCRL|CCRL 40/4]]
=References=
<references />
'''[[Engines|Up one Level]]'''
[[Category:UCI]]
[[Category:Open Source]]
[[Category:Java]]
