[EM] SSD is not BeatpathWinner

Markus Schulze markus.schulze at alumni.tu-berlin.de
Tue Dec 23 05:58:02 PST 2003

Dear Mike,

you wrote (23 Dec 2003):

> Maybe when Markus names those methods as being the same as BeatpathWinner,
> he'd like to take credit for all of them (assuming for the moment that he
> really did invent BeatpathWinner). Yes he did describe CSSD after proposing
> BeatpathWinner, pointing out the equivalence. But I doubt that he proposed
> SSD. SSD was a colaboration from discussion with Steve Eppley. Neither of us
> knew of Markus's CSSD description at that time. Later, in a discussion in
> which a clone-independent method was desired, and in which someone else was
> proposing BeatpathWinner, a method not as obviously justified as SSD, I
> changed SSD to make it clone-independent--Cloneproof SSD (CSSD). Later I
> found out that Markus had described CSSD.

In the voting recommendation to the DEBIAN project, you can find a very
interesting comment to this question. Norman Petry wrote (6 Feb 2001):

> Regardless of what names we use when referring to these methods during our
> committee discussions, I think it is appropriate that if one of these
> variants is recommended to Debian that it be named SCHULZE'S METHOD.  This
> is because:
> 1. Schulze, version 1: The 'Beat-Or-Tie-path' method was first proposed by
> Markus Schulze on Sat, 4 Oct 1997 (see EM Archives, "Re: Condorect sub-cycle
> rule").  Unfortunately, eGroups has not archived this message, but it can be
> found at Rob's site, in this text file (but mistakenly referred to there as
> "Tideman's Method"): http://www.eskimo.com/~robla/em/archive/em.97q4
> 2. Schulze, version 2: The 'Schwartz Sequential Dropping' (SSD) method was
> first proposed by Markus Schulze on Mon, 10 Aug 1998.  His description can
> be found here:
> http://groups.yahoo.com/group/election-methods-list/message/673
> 3. Schulze, version 3: The 'Cloneproof SSD' method was first proposed by
> Markus Schulze on Sat, 14 Nov 1998.  See:
> http://groups.yahoo.com/group/election-methods-list/message/2291  As noted
> above, Markus' version of 'Cloneproof SSD' uses a slightly different (and
> imo better) tiebreaker than Mike's version, but the two methods are
> otherwise identical.
> 4. Beatpath Winner: This was not specifically proposed by Markus Schulze,
> but it is equivalent in terms of results to Cloneproof SSD.  It is the same
> as 'Beat-or-tie-path' winner, except that pairties in the matrix are zeroed
> out before paths are computed, so that tied values cannot be part of the
> paths used to determine the winner.
> Since Markus was the originator of the first three of these methods, and
> usually refers to all of them as "Schulze's Method", it seems appropriate to
> name them as he has done.

Another interesting question is: In so far as you considered neither
independence of clones nor reversal symmetry to be important, why
did you propose an election method that is more complicated than

Markus Schulze

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