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are domain-independent extensions introduced in 1988 by [[Thomas Anantharaman]], [[Murray Campbell]], and [[Feng-hsiung Hsu]] <ref>[[Thomas Anantharaman]], [[Murray Campbell]], [[Feng-hsiung Hsu]] ('''1988'''). ''Singular extensions: Adding Selectivity to Brute-Force Searching''. [[AAAI ]] Spring Symposium, Computer Game Playing, pp. 8-13. Also published also in [[ICGA Journal#11_4|ICCA Journal, Vol. 11, No. 4]], republished and ('''1990''') in [https://en.wikipedia.org/wiki/Artificial_Intelligence_%28journal%29 Artificial Intelligence], Vol. 43, No. 1, pp. 99-109. ISSN 0004-3702</ref>, as implemented in [[ChipTest]] <ref>[http://groups.google.com/group/rec.games.chess/browse_frm/thread/b3b584ef5a572d79# Feng's (Deep Thought) article in Scientific American (long)] by [[Feng-hsiung Hsu]], [[Computer Chess Forums|rgc]], October 19, 1990</ref> and [[Deep Thought]]. The idea is to extend the search at expected [[Node Types#PV|PV-]] and [[Node Types#CUT|Cut-Nodes]], if one move seems to be a lot better than all of the alternatives. The problem is that one does not know in advance, and therefore has to perform a reduced search with a [[Null Window|null window]] lowered by some significant margin. Only if all alternatives fail below that window, a singular move is detected, and that move is re-searched with an extended [[Depth|depth]]. While it sounds expensive, the initial publication in 1988 reported encouraging results in tactical positions. In 1991, Anantharaman re-considered SE in comparison and interaction with other extensions, and mentioned implementation issues related to the [[Transposition Table|transposition table]] <ref>[[Thomas Anantharaman]] ('''1991'''). ''Confidently Selecting a Search Heuristic.'' [[ICGA Journal#14_1|ICCA Journal, Vol. 14, No. 1]]</ref> <ref>[[Thomas Anantharaman]] ('''1991'''). ''Extension Heuristics''. [[ICGA Journal#14_2|ICCA Journal, Vol. 14, No. 2]]</ref>. A somehow "reversed" idea compared to SE is [[Yngvi Björnsson|Björnsson's]] [[Multi-Cut]] <ref>[[Yngvi Björnsson]], [[Tony Marsland]] ('''2001'''). ''Multi-cut Alpha-Beta Pruning in Game Tree Search.'' Theoretical Computer Science, Vol. 252, pp. 177-196. [http://www.ru.is/faculty/yngvi/pdf/BjornssonM01a.pdf pdf]</ref> , to prune if in a reduced search multiple moves may [[Fail-High|fail high]].

* [[Thomas Anantharaman]], [[Murray Campbell]], [[Feng-hsiung Hsu]] ('''1988'''). ''Singular extensions: Adding Selectivity to Brute-Force Searching''. [[AAAI ]] Spring Symposium, Computer Game Playing, pp. 8-13. Also published also in [[ICGA Journal#11_4|ICCA Journal, Vol. 11, No. 4]], republished and ('''1990''') in [https://en.wikipedia.org/wiki/Artificial_Intelligence_%28journal%29 Artificial Intelligence], Vol. 43, No. 1, pp. 99-109. ISSN 0004-3702. <ref>[http://www.talkchess.com/forum/viewtopic.php?t=53713 Paper "Singular Extensions" by Anantharaman, Campbell, and Hsu (1988)] by [[Roland Stuckardt]], [[CCC]], September 15, 2014</ref>* [[Thomas Anantharaman]], [[Murray Campbell]], [[Feng-hsiung Hsu]] ('''1990'''). ''Singular Extensions: Adding Selectivity to Brute-Force Searching''. Artif[https://en.wikipedia. Intellorg/wiki/Artificial_Intelligence_%28journal%29 Artificial Intelligence], Vol. 43(, No. 1): 99-109