*To*: Ian Jackson <ijackson@chiark.greenend.org.uk>*Cc*: Michael Ossipoff <email9648742@gmail.com>, debian-vote@lists.debian.org*Subject*: Re: Norman Petry and I (Ossipoff) recommended CSSD, but Schwartz Woodall is a better voting system for Debian*From*: Kurt Roeckx <kurt@roeckx.be>*Date*: Thu, 9 May 2013 18:55:34 +0200*Message-id*: <20130509165534.GA32188@roeckx.be>*In-reply-to*: <20875.41028.602530.232404@chiark.greenend.org.uk>*References*: <CAOKDY5A1yqfArNJLiz3dwAkYEN_ZXGzJUKw6SWkNaRXfwryr7w@mail.gmail.com> <20875.41028.602530.232404@chiark.greenend.org.uk>

On Thu, May 09, 2013 at 02:10:28PM +0100, Ian Jackson wrote: > Michael Ossipoff writes ("Norman Petry and I (Ossipoff) recommended CSSD, but Schwartz Woodall is a better voting system for Debian"): > > Example 1: > > > > Sincere preferences: > > > > 99: A>B>>C > > 2: B>A>>C > > 100: C>>(A=B) > > > > The A voters rank sincerely, and the B voters defect: > > > > 99: A>B > > 2: B > > 3: C > > In Debian's system, this will result in A winning. Note that he corrected his example to 100: C > A vs B: > 99x "A>B" count as preferring A to B > 2x "B" count as preferring B to A > 3x "C" count as preferring neither A to B, nor B to A You are of course correct in this, for some reason I said B didn't compare to anything, but it would get the default value so that it's ranked lower than any voted value, and what it really says is: 99x: (A>B)>C 2x: (B)>(A=C) 100x: (C)>(A=B) > So A defeats B. > > A vs C: > 99x "A>B" count as preferring A to C > 2x "B" count as preferring neither A to C, nor C to A > 3x "C" count as preferring C to A > So A defeats C. So the corrected example would have 99 prefered A to C,en 100 C to A, making C the winner, so 1 more prefering C over A than A over C and making C defeat A. > The Schwartz set contains only A. The corrected example would contain C. > > ---------------------------- > > > > Here's another example in which the 3 factions are nearly equal in size: > > > > Sincere preferences: > > > > 33: A>B>>C > > 32: B>A>>C > > 34: C>>(A=B) > > > > Actual votes, when A voters co-operate and B voters defect: > > > > 33: A>B > > 32: B > > 34: C So that needs to be translated to: 33: A>B>C 32: B>(A=C) 34: C>(A=B) > A vs B: > 33x "A>B" count as A>B > 32x "B" count as B>A > 34x "C" count neither way > A defeats B by 33:32 > > A vs C: > 33x "A>B" count as A>C > 32x "B" count neither way > 34x "C" count as C>A > C defeats A by 34:33 > > B vs C: > 33x "A>B" count as B>C > 32x "B" count as B>C > 34x "C" count as C>B > B defeats C by 65:34 > > The Schwarz set contains A,B,C. We drop the weakest defeat, which is > A>B by one vote because 33<34. I think we shoud drop both both B and A because they are both defeated by 1. And C would be the winner. Note that A defeats B, which defeats C, which defeats A again. Kurt

**References**:**Norman Petry and I (Ossipoff) recommended CSSD, but Schwartz Woodall is a better voting system for Debian***From:*Michael Ossipoff <email9648742@gmail.com>

**Re: Norman Petry and I (Ossipoff) recommended CSSD, but Schwartz Woodall is a better voting system for Debian***From:*Ian Jackson <ijackson@chiark.greenend.org.uk>

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