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'''[[Main Page|Home]] * [[People]] * Markian Hlynka'''
[[FILE:markian.jpg|border|right|thumb|link=http://webdocs.cs.ualberta.ca/~darse/Photos/Friends/| Markian Hlynka <ref>[http://webdocs.cs.ualberta.ca/~darse/Photos/Friends/ Photo Gallery: Friends and Peers] by [[Darse Billings]]</ref> ]]
'''Markian Hlynka''',<br/>
a Canadian computer scientist and systems analyst at [[University of Alberta]]. Along with [[Jonathan Schaeffer]] et al., Markian Hlynka researched and published on [[Search|search]] enhancements and [[Temporal Difference Learning|temporal difference learning]].
<span id="PreSearching"></span>
=Pre-Search=
<ref>[[Markian Hlynka]], [[Jonathan Schaeffer]] ('''2004'''). ''Pre-Searching''. [[ICGA Journal#27_4|ICGA Journal, Vol. 27, No. 4]]</ref>
==Abstract==
This paper introduces the idea of pre-searching a position — searching it before [[Alpha-Beta|αβ]] determines that it needs to be searched. Consider the case where an iteration of αβ search comes across a position p that needs to be searched to [[Depth|depth]] d1, and the [[Transposition Table|transposition table]] reveals that p will likely need to be searched later in that iteration to depth d2 greater than d1. Pre-searching involves speculatively searching p to depth d2, even though it has not been demonstrated that search to this depth is needed. If the gamble is successful, then additional accuracy is introduced to the search (using a result with extra search depth d2 − d1). While any search extension scheme is not without some risk, empirical results indicate that the impact on the αβ search tree size is small, but the additional accuracy that is introduced improves program performance.
==Pseudo Code==
<pre>
// Assumptions:
// * search depth counts down to 0 (leaf node)
// * IDDepth is the iterative deepening search depth
// * searches are to a fixed depth
int AlphaBeta( state, depth, alpha, beta, presearch ) {
if( TerminalNode( state ) || depth == 0 )
return( Evaluate( state ) );
save_alpha = alpha;
save_beta = beta;
tt_found = TTLook( state, &tt_depth, &tt_value, &tt_bound, &tt_iteration );
if( tt_found == TRUE && tt_depth >= depth ) { if( tt_bound == LOWER ) alpha = MAX( alpha, tt_score ); if( tt_bound == UPPER ) beta = MIN( beta, tt_score ); if( tt_bound == ACCURATE ) alpha = beta = tt_bound; if( alpha >= beta ) return( alpha ); } // Check for pre-search conditions if( tt_found && // node is in TT tt_iteration != IDDepth && // not updated this iteration // Check that entry has deeper search needs tt_depth + ( IDDepth - tt_iteration) >= depth ) { // Found a shallow node new_depth = tt_depth + ( IDDepth - tt_iteration ); if( presearchFilter( newdepth, depth, tt_depth, tt_iteration, presearch ) == YES ) { presearch = TRUE; depth = new_depth; } } score =Pre-SearchINFINITY; num_moves = Generate( state, moves[] ); for( i = 1; i <span id="PreSearching"num_moves; i++ ) { result = -AlphaBeta( state.moves[i], depth-1, -beta, -alpha, presearch ); score = MAX( score, result ); alpha = MAX( alpha, score ); if( alpha >= beta ) break; } // Normal TT update, but need to also save IDDepth TTUpdate( state, score, save_alpha, save_beta, depth, IDDepth ); return( score );}</span>''Abstract'' <refpre>=Fotos=[[Markian HlynkaFILE:Olympiad2005Go9x9.JPG|none|border|text-bottom|640px|link=http://www.iis.sinica.edu.tw/Conference/ICGA2005/icga/img/2005_09_04/slides/IMG_0255.html]], [[Jonathan Schaeffer10th Computer Olympiad]] ('''2004'''). ''Pre-Searching''. , [[ICGA Journal10th Computer Olympiad#27_4Go9x9|ICGA JournalGo 9x9]], Vol[https://en.wikipedia. 27org/wiki/Taipei Taipei] 2005, No. 4[[Shih-Chieh Huang]] and [[Markian Hlynka]]operating<br/ref> This paper introduces the idea of pre[https://www.game-ai-forum.org/icga-searching a position — searching it before αβ determines that it needs to be searchedtournaments/program. Consider the case where an iteration of αβ search comes across a position p that needs to be searched to depth d1, php?id=98 Go Intellect] and the transposition table reveals that p will likely need to be searched later in that iteration to depth d2 greater than d1[https://www.game-ai-forum. Preorg/icga-searching involves speculatively searching p to depth d2tournaments/program.php?id=104 NeuroGo], even though it has not been demonstrated that search to this depth is needed[[Fredrik Niemelä]] watching <ref>[http://www.iis.sinica.edu. If the gamble is successful, then additional accuracy is introduced to the search (using a result with extra search depth d2 − d1)tw/Conference/ICGA2005/icga/e1. While any search extension scheme is not without some riskhtm CO 10 and ACG 11], empirical results indicate that the impact on the αβ search tree size is small, but the additional accuracy that is introduced improves program performance. Pictures 09/04/2005</ref>
=Selected Publications=
<ref>[https://dblp.org/pers/hd/h/Hlynka:Markian .html dblp: Markian Hlynka]</ref>* [[Jonathan Schaeffer]], [[Markian Hlynka]], [[Vili Jussila]] ('''2001'''). ''[https://www.semanticscholar.org/paper/Temporal-Difference-Learning-Applied-to-a-Program-Schaeffer-Hlynka/85941af287e2158bd201a633cbcc763693652c7f Temporal Difference Learning Applied to a High-Performance Game-Playing Program]''. [http://www.informatik.uni-trier.de/~ley/db/conf/ijcai/ijcai2001.html[Conferences#SchaefferHJ01 IJCAI2001|CGW@IJCAI 2001]]
* [[Markian Hlynka]], [[Jonathan Schaeffer]] ('''2004'''). ''Pre-Searching''. [[ICGA Journal#27_4|ICGA Journal, Vol. 27, No. 4]], [http://webdocs.cs.ualberta.ca/~jonathan/publications/ai_publications/PreSearch.pdf pdf]
* [[Markian Hlynka]], [[Jonathan Schaeffer]] ('''2005'''). ''[httphttps://link.springer.com/chapter/10.1007/11922155_3 Automatic Generation of Search Engines]''. [[Advances in Computer Games 11]]
=External Links=
* [https://web.archive.org/web/20180727083721/https://ist.ualberta.ca/blog/culture/full-circle Markian Hlynka Full Circle | Information Services and Technology UoA]([https://en.wikipedia.org/wiki/Wayback_Machine Wayback Machine], July 2018)
=References=
<references />
'''[[People|Up one level]]'''
[[Category:Researcher|Hlynka]]
