Difference between revisions of "Aspiration Windows"
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'''[[Main Page|Home]] * [[Search]] * [[Alpha-Beta]] * Aspiration Windows''' | '''[[Main Page|Home]] * [[Search]] * [[Alpha-Beta]] * Aspiration Windows''' | ||
− | [[FILE:TheNon-EuclideanWindow.JPG|border|right|thumb|The Non-Euclidean Window <ref>[[ | + | [[FILE:TheNon-EuclideanWindow.JPG|border|right|thumb|The Non-Euclidean Window <ref>[[:Category:Gerhard Hoehme|Gerhard Hoehme]] - The Non-Euclidean Window (1964), mixed technique / wood on canvas, [[:Category:Art Museum Bochum|Art Museum]], [https://en.wikipedia.org/wiki/Bochum Bochum], [https://en.wikipedia.org/wiki/North_Rhine-Westphalia North Rhine-Westphalia], [https://en.wikipedia.org/wiki/Germany Germany], Photo by [[Gerd Isenberg]], October 30, 2016</ref> ]] |
'''Aspiration windows''' are a way to reduce the [[Search Space|search space]] in an alpha-beta search. The technique is to use a guess of the expected value (usually from the last iteration in [[Iterative Deepening|iterative deepening]]), and use a [[Window|window]] around this as the alpha-beta [[Bound|bounds]]. Because the window is narrower, more beta cutoffs are achieved, and the search takes a shorter time. The drawback is that if the true score is outside this window, then a costly re-search must be made. Typical window sizes are 1/2 to 1/4 of a pawn on either side of the guess. | '''Aspiration windows''' are a way to reduce the [[Search Space|search space]] in an alpha-beta search. The technique is to use a guess of the expected value (usually from the last iteration in [[Iterative Deepening|iterative deepening]]), and use a [[Window|window]] around this as the alpha-beta [[Bound|bounds]]. Because the window is narrower, more beta cutoffs are achieved, and the search takes a shorter time. The drawback is that if the true score is outside this window, then a costly re-search must be made. Typical window sizes are 1/2 to 1/4 of a pawn on either side of the guess. | ||
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instead. However, a fully fledged search is typically full of [[Search Instability|search instability]], and it will often happen that the above re-search will fail low! This is why it is best to only widen the bound that fails, and leave the other bound unchanged. | instead. However, a fully fledged search is typically full of [[Search Instability|search instability]], and it will often happen that the above re-search will fail low! This is why it is best to only widen the bound that fails, and leave the other bound unchanged. | ||
− | Modern engines, like [[ | + | Modern engines, like [[RobboLito]] or [[Stockfish]], start with a rather small aspiration window, and increase the bound that fails in an exponential fashion. |
=PVS and Aspiration= | =PVS and Aspiration= | ||
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* [http://www.talkchess.com/forum/viewtopic.php?t=46837 Aspiration Windows] by [[Jerry Donald]], [[CCC]], January 11, 2013 | * [http://www.talkchess.com/forum/viewtopic.php?t=46837 Aspiration Windows] by [[Jerry Donald]], [[CCC]], January 11, 2013 | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=47996 Aspiration windows] by [[Marco Pampaloni]], [[CCC]], May 14, 2013 | * [http://www.talkchess.com/forum/viewtopic.php?t=47996 Aspiration windows] by [[Marco Pampaloni]], [[CCC]], May 14, 2013 | ||
− | * [http://www.talkchess.com/forum/viewtopic.php?t=53972 Your experience with PVS + Aspiration window] by [[Fabio Gobbato]], [[CCC]], October 07, 2014 » [[Principal Variation Search]], [[PVS and | + | * [http://www.talkchess.com/forum/viewtopic.php?t=53972 Your experience with PVS + Aspiration window] by [[Fabio Gobbato]], [[CCC]], October 07, 2014 » [[Principal Variation Search]], [[PVS and Aspiration]] |
* [http://www.talkchess.com/forum/viewtopic.php?t=54241 Solving a fail low situation at the root] by [[Alberto Sanjuan]], [[CCC]], November 03, 2014 » [[Fail-Low]] | * [http://www.talkchess.com/forum/viewtopic.php?t=54241 Solving a fail low situation at the root] by [[Alberto Sanjuan]], [[CCC]], November 03, 2014 » [[Fail-Low]] | ||
==2015 ...== | ==2015 ...== | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=57113 Parallel aspiration windows] by [[Giuseppe Cannella]], [[CCC]], July 29, 2015 | * [http://www.talkchess.com/forum/viewtopic.php?t=57113 Parallel aspiration windows] by [[Giuseppe Cannella]], [[CCC]], July 29, 2015 | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=58542 Restarting iterative deepening] by [[Harm Geert Muller]], [[CCC]], December 09, 2015 » [[Fail-Low]], [[Iterative Deepening]] | * [http://www.talkchess.com/forum/viewtopic.php?t=58542 Restarting iterative deepening] by [[Harm Geert Muller]], [[CCC]], December 09, 2015 » [[Fail-Low]], [[Iterative Deepening]] | ||
− | |||
* [http://www.talkchess.com/forum/viewtopic.php?t=60285 Dynamic aspiration window] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], May 26, 2016 | * [http://www.talkchess.com/forum/viewtopic.php?t=60285 Dynamic aspiration window] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], May 26, 2016 | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=60402 Aspiration Windows on the root search -- Determining margin] by [[Andrew Grant]], [[CCC]], June 08, 2016 | * [http://www.talkchess.com/forum/viewtopic.php?t=60402 Aspiration Windows on the root search -- Determining margin] by [[Andrew Grant]], [[CCC]], June 08, 2016 | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=60916 Iterative Deepening Question] by [[David Cimbalista]], [[CCC]], July 23, 2016 » [[Iterative Deepening]] | * [http://www.talkchess.com/forum/viewtopic.php?t=60916 Iterative Deepening Question] by [[David Cimbalista]], [[CCC]], July 23, 2016 » [[Iterative Deepening]] | ||
* [http://www.open-chess.org/viewtopic.php?f=5&t=2995 Aspiration window with TT question] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], August 01, 2016 » [[Transposition Table]] | * [http://www.open-chess.org/viewtopic.php?f=5&t=2995 Aspiration window with TT question] by [[Sander Maassen vd Brink|sandermvdb]], [[Computer Chess Forums|OpenChess Forum]], August 01, 2016 » [[Transposition Table]] | ||
− | ''' | + | '''2017 ...''' |
* [http://www.talkchess.com/forum/viewtopic.php?t=63706 Conceptual question on aspiration windows] by Jacob Wilkins, [[CCC]], April 09, 2017 | * [http://www.talkchess.com/forum/viewtopic.php?t=63706 Conceptual question on aspiration windows] by Jacob Wilkins, [[CCC]], April 09, 2017 | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=64321 (I)ID and PV dropout] by [[Harm Geert Muller]], [[CCC]], June 17, 2017 » [[Fail-Low]], [[Internal Iterative Deepening]], [[Iterative Deepening]] | * [http://www.talkchess.com/forum/viewtopic.php?t=64321 (I)ID and PV dropout] by [[Harm Geert Muller]], [[CCC]], June 17, 2017 » [[Fail-Low]], [[Internal Iterative Deepening]], [[Iterative Deepening]] | ||
* [http://www.talkchess.com/forum/viewtopic.php?t=65589 Aspiration window problem] by [[Sander Maassen vd Brink]], [[CCC]], October 30, 2017 | * [http://www.talkchess.com/forum/viewtopic.php?t=65589 Aspiration window problem] by [[Sander Maassen vd Brink]], [[CCC]], October 30, 2017 | ||
+ | * [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=68278&start=16 Re: Lazy SMP ideas] by [[Folkert van Heusden]], [[CCC]], October 03, 2018 » [[Lazy SMP]] | ||
+ | * [http://www.talkchess.com/forum3/viewtopic.php?f=7&t=69627 Impact of Aspiration on tree size] by Frank Kopp, [[CCC]], January 16, 2019 | ||
=External Links= | =External Links= | ||
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'''[[Alpha-Beta|Up one level]]''' | '''[[Alpha-Beta|Up one level]]''' | ||
− | [[Category:Industrial | + | [[Category:Gerhard Hoehme]] |
+ | [[Category:Art Museum Bochum]] | ||
+ | [[Category:Industrial Heritage Trail]] |
Revision as of 10:41, 18 January 2019
Home * Search * Alpha-Beta * Aspiration Windows
Aspiration windows are a way to reduce the search space in an alpha-beta search. The technique is to use a guess of the expected value (usually from the last iteration in iterative deepening), and use a window around this as the alpha-beta bounds. Because the window is narrower, more beta cutoffs are achieved, and the search takes a shorter time. The drawback is that if the true score is outside this window, then a costly re-search must be made. Typical window sizes are 1/2 to 1/4 of a pawn on either side of the guess.
Contents
Gradual Widening
Some programs, such as Crafty, also use a gradual widening on re-searches. For instance, if the window is, in pawns:
[g - 1/4, g + 1/4]
and the search fails high, the next search would be
[g - 1/4, g + 1]
It's important to note that the bound that didn't fail is unchanged. In a basic alpha-beta without search instability, one could have done the next search on
[g + 1/4, g + 1]
instead. However, a fully fledged search is typically full of search instability, and it will often happen that the above re-search will fail low! This is why it is best to only widen the bound that fails, and leave the other bound unchanged.
Modern engines, like RobboLito or Stockfish, start with a rather small aspiration window, and increase the bound that fails in an exponential fashion.
PVS and Aspiration
Using aspiration windows together with the principal variation search (PVS) causes some additional complications.
See also
Publications
- Hermann Kaindl, Reza Shams, Helmut Horacek (1991). Minimax Search Algorithms with and without Aspiration Windows. IEEE Transactions on Pattern Analysis and Machine Intelligence, Vol. 13, No. 12
- Reza Shams, Hermann Kaindl, Helmut Horacek (1991). Using Aspiration Windows for Minimax Algorithms. IJCAI 1991, pdf
Forum Posts
1995 ...
- Question about aspiration window by Werner Inmann, CCC, August 14, 1998
- aspiration windows by James Long, CCC, November 27, 1998
- Aspiration Rules... by Chris Pile, rgcc, February 5, 1999
- Aspiration search by James Robertson, CCC, April 20, 1999
- Aspiration search by Scott Gasch, CCC, August 13, 1999
2000 ...
- Aspiration window by Bas Hamstra, CCC, January 20, 2002
- Exact value of second best move in AlphaBeta with aspiration Window by Martin Bauer, CCC, August 01, 2002
- Aspiration search, PVS by Russell Reagan, CCC, December 28, 2002
- Unstable aspiration search by Sune Fischer, CCC, February 10, 2003
- Question about aspiration search by Jaime Benito de Valle Ruiz, CCC, March 23, 2004
- What is a common Aspiration window? by Joachim Rang, CCC, March 26, 2004
- aspiration search question by Daniel Shawul, CCC, May 13, 2004
- Q. Aspiration, PVS, Fail-Soft by David B. Weller, CCC, July 02, 2004
- PVS and aspiration windows by Tord Romstad, CCC, August 06, 2004
2005 ...
- Aspiration Window sizes by Renze Steenhuisen, CCC, March 14, 2005
- Bounds for aspiration window re-search by Sven Schüle, CCC, March 17, 2009
- A way to improve PVS by Sergei S. Markoff, CCC, September 07, 2009
2010 ...
- Apiration window by Don Dailey, CCC, March 27, 2010
- A few general questions... by Bill Henry, CCC, January 29, 2012 » Root, Exact Score
- optimal aspiration window for stockfish question by Uri Blass, CCC, March 12, 2012 » Stockfish
- Aspiration Windows: Rubbish! by Matthew R. Brades, CCC, July 16, 2012
- Aspiration window - effect? Issue with hashtables?! by Jens Bæk Nielsen, CCC, December 28, 2012
- Aspiration Windows by Jerry Donald, CCC, January 11, 2013
- Aspiration windows by Marco Pampaloni, CCC, May 14, 2013
- Your experience with PVS + Aspiration window by Fabio Gobbato, CCC, October 07, 2014 » Principal Variation Search, PVS and Aspiration
- Solving a fail low situation at the root by Alberto Sanjuan, CCC, November 03, 2014 » Fail-Low
2015 ...
- Parallel aspiration windows by Giuseppe Cannella, CCC, July 29, 2015
- Restarting iterative deepening by Harm Geert Muller, CCC, December 09, 2015 » Fail-Low, Iterative Deepening
- Dynamic aspiration window by Sergei S. Markoff, CCC, May 26, 2016
- Aspiration Windows on the root search -- Determining margin by Andrew Grant, CCC, June 08, 2016
- Iterative Deepening Question by David Cimbalista, CCC, July 23, 2016 » Iterative Deepening
- Aspiration window with TT question by sandermvdb, OpenChess Forum, August 01, 2016 » Transposition Table
2017 ...
- Conceptual question on aspiration windows by Jacob Wilkins, CCC, April 09, 2017
- (I)ID and PV dropout by Harm Geert Muller, CCC, June 17, 2017 » Fail-Low, Internal Iterative Deepening, Iterative Deepening
- Aspiration window problem by Sander Maassen vd Brink, CCC, October 30, 2017
- Re: Lazy SMP ideas by Folkert van Heusden, CCC, October 03, 2018 » Lazy SMP
- Impact of Aspiration on tree size by Frank Kopp, CCC, January 16, 2019
External Links
- Aspiration Windows from Bruce Moreland's Programming Topics
- Aspiration from Wikipedia
- aspiration - Wiktionary
- aspire - Wiktionary
References
- ↑ Gerhard Hoehme - The Non-Euclidean Window (1964), mixed technique / wood on canvas, Art Museum, Bochum, North Rhine-Westphalia, Germany, Photo by Gerd Isenberg, October 30, 2016