[EM] Steph's Condorcet example
MIKE OSSIPOFF
nkklrp at hotmail.com
Mon Jan 13 21:56:40 PST 2003
There was a question about Condorcet returning a tie in this
example:
Input matrix
0 23 25 65
24 0 11 87
44 55 0 22
33 11 44 0
Initial defeats matrix:
0 0 0 65
24 0 0 87
44 55 0 0
0 0 44 0
When defeat-strengths are measured by winning votes:
When we deal with equal defeats by comparing their margins:
BeatpathWinner/CSSD chooses A
Ranked-Pairs chooses C
When we treat equal defeats as equal, instead of looking at margins:
BeatpathWinner/CSSD chooses A & C
Ranked-Pairs chooses C.
When Ranked-Pairs encounters 2 or more equally strongest unconsidered
defeats, and either we simply call those defeats equal, or
when we compare margins, they're equal too, I've proposed a way
for RP to deal with those equally strongest unconsidered defeats:
Call them the "tie-defeats". A tie defeat is "qualified" if it
isn't in a cycle consisting only of itself and some kept defeats.
Keep a qualified tie defeat if it isn't in a cycle consisting only
of itself and some combination of kept defeats and qualified defeats.
Mike Ossipoff
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