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'''[[Main Page|Home]] * [[Engines]] * Querg'''
[[FILE:Singular dwarf by Frølich.jpg|border|right|thumb|Dwarf <ref>A singular, small depiction of a rather gnarly-looking [https://en.wikipedia.org/wiki/Dwarf_(mythology) dwarf] appearing with the list of dwarves in the [https://en.wikipedia.org/wiki/Poetic_Edda Poetic Edda] poem [https://en.wikipedia.org/wiki/V%C3%B6lusp%C3%A1 Völuspá], Painting by [https://en.wikipedia.org/wiki/Lorenz_Fr%C3%B8lich Lorenz Frølich] in [https://en.wikipedia.org/wiki/Karl_Adolph_Gjellerup Karl Gjellerup] ('''1895'''). ''[https://archive.org/details/denldreeddasgud00saemgoog Den ældre Eddas Gudesange]''.</ref> ]]
'''Querg''',<br/>
a series of [[Private Engines|private chess programs]] written by [[John F. White]] in [[6502]] [[Assembly|assembly]] to run on an 64K [[Atari 8-bit|Atari 130XE]], as described in the [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]], 1988 <ref>[[John F. White]] ('''1988'''). ''Querg Chess''. [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]]</ref>. Versions mentioned in the article were dubbed ''NovaQuerg'' and ''SuperQuerg''. In his second [[ICGA Journal#13_1|ICCA Journal]] article, White describes how to store and retrieve moves of an [[Opening Book|opening book]] <ref>[[John F. White]] ('''1990'''). ''The Amateur's Book-Opening Routine''. [[ICGA Journal#13_1|ICCA Journal, Vol. 13, No. 1]]</ref>.
=Etymology=
The name Querg <ref>In the German [https://en.wikipedia.org/wiki/Colognian_dialect Colognian dialect]] a Querg appeared to be a [https://en.wikipedia.org/wiki/Dwarf_(mythology) dwarf] or [https://en.wikipedia.org/wiki/Heinzelm%C3%A4nnchen Heinzelmännchen], [http://woerterbuchnetz.de/RhWB/call_wbgui_py_from_form?sigle=RhWB&mode=Volltextsuche&hitlist=&patternlist=&lemid=RQ00937 Wörterbuchnetz - Rheinisches Wörterbuch] (German)</ref> has no meaning, the ''Querg P Quigel'' fictional character <ref>[http://pathfinderfl.wordpress.com/2011/02/26/i-querg-p-quigel/ I, Querg P Quigel « Pathfinder's Federation Log]</ref> from [https://en.wikipedia.org/wiki/Star_Trek:_Voyager Star Trek Voyager] [https://en.wikipedia.org/wiki/Pathfinder_%28Star_Trek:_Voyager%29 Pathfinder] appeared some years later.
=Description=
==Move Generation==
Most versions of Querg use a [[Mailbox|mailbox]] based offset [[Move Generation|move generation]], [[0x88]] techniques coupled with offset move generation are mentioned in the article, and that this technique has advantages for in [[Check#Detection|check detection]] as applied in [[Paul Wiereyn|Paul Wiereyn's]] mate finding program <ref>[[Paul Wiereyn]] ('''1985'''). ''Inventive Problem Solving''. [[ICGA Journal#8_4|ICCA Journal, Vol. 8, No. 4]]</ref>. The experiments with [[Incremental Updates|incremental updated]] [[Move List|movelists]] were not that successful.
==Check Detection==
[[Check|Checks]] were first [[Check#Detection|detected]] by a variant of the method given by Wiereyn, modified to suit a cylindrical representation of the chess board, and rather slower than the original described - the 12 x 10 board is not well suited to implementation of this procedure. The alternative method to delay check detection until a king has been captured saved time in positions where checks are rare, but was inefficient if kings are vulnerable to checks. Finally, White came up with a technique to determine whether pieces give check during generation time.
==Search==
Querg applies [[Principal Variation Search|PVS]] with [[Aspiration Windows|Aspiration windows]] within an [[Iterative Deepening|iterative deepening]] framework, where the [[Principal Variation|principal variation]] is 'fed over' into the next iteration. Two [[Killer Move|killer moves]] were stored and used to [[Killer Heuristic|reject moves]]. Lazy move generation of [[PV-Move|PV-]] and killer moves before constructing a whole move list failed to provide any benefit. Forcing moves, that is [[Check|checks]] and replies to check, [[Promotions|promotions]], threats of promotions by the side not to move, and [[Captures|captures]], are [[Extensions|extended]] by a maximum of three additional plies in the whole path. A special routine ''HIPL'' (high-ply-[[Pruning|pruning]]) avoids the unnecessary sequence [[Make Move|make move]] -> [[Evaluation|evaluate]] -> [[Unmake Move|unmake move]] at [[Frontier Nodes|frontier nodes]] for none forcing moves.
==Evaluation==
The [[Evaluation|evaluation]] relies largely on first-order terms <ref>[[Jan Eric Larsson]] ('''1987'''). ''Challenging that Mobility is Fundamental''. [[ICGA Journal#10_3|ICCA Journal, Vol. 10, No. 3]]</ref>, considering [[Material|material]], pieces left [[En prise|en prise]], [[Mobility|mobility]] as number of moves plus information from [[Piece-Square Tables|piece-square tables]], and [[Pawn Structure|pawn structure]].
=Performance=
Performance was determined by [[Test-Positions|test-positions]] and games played versus programs running on the same 8-bit Atari, such as [[Cyrus]], [[Colossus Chess|Colossus 3.0]], the old [[Sargon|Sargon 2.5]], and others, where ''NovaQuerg'' finished with 6.5 points out of 14. However, Querg has not played any official tournaments.
=See also=
* [[Various Classifications#Startrek|Star Trek]]
* [[Quark]]
=Publications=
<ref>[http://ilk.uvt.nl/icga/journal/docs/References.pdf ICGA Reference Database] (pdf)</ref>
* [[John F. White]] ('''1988'''). ''Querg Chess''. [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]]
* [[John F. White]] ('''1990'''). ''The Amateur's Book-Opening Routine''. [[ICGA Journal#13_1|ICCA Journal, Vol. 13, No. 1]]
=External Links=
* [http://www.mobygames.com/game/querg-draughts Querg Draughts for Atari ST (1994) - MobyGames]
* [http://pathfinderfl.wordpress.com/2011/02/26/i-querg-p-quigel/ I, Querg P Quigel « Pathfinder's Federation Log]
* [http://pathfinderfl.wordpress.com/stotoons/querg/ Lt Cmd Querg « Pathfinder's Federation Log]
=References=
<references />
'''[[Engines|Up one level]]'''
[[FILE:Singular dwarf by Frølich.jpg|border|right|thumb|Dwarf <ref>A singular, small depiction of a rather gnarly-looking [https://en.wikipedia.org/wiki/Dwarf_(mythology) dwarf] appearing with the list of dwarves in the [https://en.wikipedia.org/wiki/Poetic_Edda Poetic Edda] poem [https://en.wikipedia.org/wiki/V%C3%B6lusp%C3%A1 Völuspá], Painting by [https://en.wikipedia.org/wiki/Lorenz_Fr%C3%B8lich Lorenz Frølich] in [https://en.wikipedia.org/wiki/Karl_Adolph_Gjellerup Karl Gjellerup] ('''1895'''). ''[https://archive.org/details/denldreeddasgud00saemgoog Den ældre Eddas Gudesange]''.</ref> ]]
'''Querg''',<br/>
a series of [[Private Engines|private chess programs]] written by [[John F. White]] in [[6502]] [[Assembly|assembly]] to run on an 64K [[Atari 8-bit|Atari 130XE]], as described in the [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]], 1988 <ref>[[John F. White]] ('''1988'''). ''Querg Chess''. [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]]</ref>. Versions mentioned in the article were dubbed ''NovaQuerg'' and ''SuperQuerg''. In his second [[ICGA Journal#13_1|ICCA Journal]] article, White describes how to store and retrieve moves of an [[Opening Book|opening book]] <ref>[[John F. White]] ('''1990'''). ''The Amateur's Book-Opening Routine''. [[ICGA Journal#13_1|ICCA Journal, Vol. 13, No. 1]]</ref>.
=Etymology=
The name Querg <ref>In the German [https://en.wikipedia.org/wiki/Colognian_dialect Colognian dialect]] a Querg appeared to be a [https://en.wikipedia.org/wiki/Dwarf_(mythology) dwarf] or [https://en.wikipedia.org/wiki/Heinzelm%C3%A4nnchen Heinzelmännchen], [http://woerterbuchnetz.de/RhWB/call_wbgui_py_from_form?sigle=RhWB&mode=Volltextsuche&hitlist=&patternlist=&lemid=RQ00937 Wörterbuchnetz - Rheinisches Wörterbuch] (German)</ref> has no meaning, the ''Querg P Quigel'' fictional character <ref>[http://pathfinderfl.wordpress.com/2011/02/26/i-querg-p-quigel/ I, Querg P Quigel « Pathfinder's Federation Log]</ref> from [https://en.wikipedia.org/wiki/Star_Trek:_Voyager Star Trek Voyager] [https://en.wikipedia.org/wiki/Pathfinder_%28Star_Trek:_Voyager%29 Pathfinder] appeared some years later.
=Description=
==Move Generation==
Most versions of Querg use a [[Mailbox|mailbox]] based offset [[Move Generation|move generation]], [[0x88]] techniques coupled with offset move generation are mentioned in the article, and that this technique has advantages for in [[Check#Detection|check detection]] as applied in [[Paul Wiereyn|Paul Wiereyn's]] mate finding program <ref>[[Paul Wiereyn]] ('''1985'''). ''Inventive Problem Solving''. [[ICGA Journal#8_4|ICCA Journal, Vol. 8, No. 4]]</ref>. The experiments with [[Incremental Updates|incremental updated]] [[Move List|movelists]] were not that successful.
==Check Detection==
[[Check|Checks]] were first [[Check#Detection|detected]] by a variant of the method given by Wiereyn, modified to suit a cylindrical representation of the chess board, and rather slower than the original described - the 12 x 10 board is not well suited to implementation of this procedure. The alternative method to delay check detection until a king has been captured saved time in positions where checks are rare, but was inefficient if kings are vulnerable to checks. Finally, White came up with a technique to determine whether pieces give check during generation time.
==Search==
Querg applies [[Principal Variation Search|PVS]] with [[Aspiration Windows|Aspiration windows]] within an [[Iterative Deepening|iterative deepening]] framework, where the [[Principal Variation|principal variation]] is 'fed over' into the next iteration. Two [[Killer Move|killer moves]] were stored and used to [[Killer Heuristic|reject moves]]. Lazy move generation of [[PV-Move|PV-]] and killer moves before constructing a whole move list failed to provide any benefit. Forcing moves, that is [[Check|checks]] and replies to check, [[Promotions|promotions]], threats of promotions by the side not to move, and [[Captures|captures]], are [[Extensions|extended]] by a maximum of three additional plies in the whole path. A special routine ''HIPL'' (high-ply-[[Pruning|pruning]]) avoids the unnecessary sequence [[Make Move|make move]] -> [[Evaluation|evaluate]] -> [[Unmake Move|unmake move]] at [[Frontier Nodes|frontier nodes]] for none forcing moves.
==Evaluation==
The [[Evaluation|evaluation]] relies largely on first-order terms <ref>[[Jan Eric Larsson]] ('''1987'''). ''Challenging that Mobility is Fundamental''. [[ICGA Journal#10_3|ICCA Journal, Vol. 10, No. 3]]</ref>, considering [[Material|material]], pieces left [[En prise|en prise]], [[Mobility|mobility]] as number of moves plus information from [[Piece-Square Tables|piece-square tables]], and [[Pawn Structure|pawn structure]].
=Performance=
Performance was determined by [[Test-Positions|test-positions]] and games played versus programs running on the same 8-bit Atari, such as [[Cyrus]], [[Colossus Chess|Colossus 3.0]], the old [[Sargon|Sargon 2.5]], and others, where ''NovaQuerg'' finished with 6.5 points out of 14. However, Querg has not played any official tournaments.
=See also=
* [[Various Classifications#Startrek|Star Trek]]
* [[Quark]]
=Publications=
<ref>[http://ilk.uvt.nl/icga/journal/docs/References.pdf ICGA Reference Database] (pdf)</ref>
* [[John F. White]] ('''1988'''). ''Querg Chess''. [[ICGA Journal#11_23|ICCA Journal, Vol. 11, Nos. 2/3]]
* [[John F. White]] ('''1990'''). ''The Amateur's Book-Opening Routine''. [[ICGA Journal#13_1|ICCA Journal, Vol. 13, No. 1]]
=External Links=
* [http://www.mobygames.com/game/querg-draughts Querg Draughts for Atari ST (1994) - MobyGames]
* [http://pathfinderfl.wordpress.com/2011/02/26/i-querg-p-quigel/ I, Querg P Quigel « Pathfinder's Federation Log]
* [http://pathfinderfl.wordpress.com/stotoons/querg/ Lt Cmd Querg « Pathfinder's Federation Log]
=References=
<references />
'''[[Engines|Up one level]]'''
