Smith//IRV: Difference between revisions
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== Notes ==
Smith//IRV passes [[ISDA]] (Independence of Smith-dominated Alternatives) but fails mono-add-plump (adding in ballots that bullet vote the winner shouldn't make the winner lose), which is the opposite of several other Condorcet-IRV hybrids. <ref name="Green 2001 four">{{cite journal | last=Green-Armytage |first=J. |title=Four Condorcet-Hare hybrid methods for single-winner elections | journal=Voting matters | issue=29 | pages=1–14 | year=2011 | url=http://www.votingmatters.org.uk/ISSUE29/I29P1.pdf}}</ref>
Smith//IRV's [[summability criterion|precinct-summability]] depends on how large the Smith Set is: while a non-summable method like IRV requires O(c!) space in the worst case, Smith//IRV only requires O(k!), where k is the number of candidates in the Smith set. However, it's not possible to decide beforehand how large the Smith set will be; any such restriction will cause the method to violate universal domain. Thus, Smith//IRV is non-summable in full generality.
One hybrid of Smith//IRV and [[Benham's Method|Benham's method]] would be "eliminate everyone outside the Smith Set, then do IRV, but before each elimination, elect the Condorcet winner (based solely on pairwise matchups between uneliminated candidates) if there is one."
Some discussion on Smith//IRV
==See also==
*[[Instant-runoff voting]]
==References==
[[Category:Single-winner voting methods]]
[[Category:Preferential voting methods]]
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