Talk:Schulze method

MinMax set and prudence criteria

Stubs for these 2 criteria would be nice too. --Wat 20

I tried to add a Column for MinMax to the table, but changing the template is not changing it on the Schulze Method page. Not sure why. Schulze Method passes MinMax criterion but Ranked Pairs (Tideman) does not, and this table should include that information to help differentiate the two. --Owen — Preceding unsigned comment added by 71.201.20.135 (talk) 17:55, 28 May 2016 (UTC)

I am open to "MiniMax criterion". Is there a citation or reference to this criterion? I would like to understand better. My understanding of the MiniMax article is that the Minimax decision for a given player is the choice that will give the least worst outcome given the range of choices by the other players in a game; hence uncertainty is intrinsic to the principle, but I see a contradiction with regard to application to a preference aggregation algorithm where the voters preferences are certain. Meanwhile, my understanding with regard to preference aggregation algorithms, MiniMax is a heuristic that chooses the alternative with the least-worst pairwise defeat against other alternatives. However, I believe that Schulze returns different output than MiniMax voting methods, correct? If so, I am wondering how Schulze can satisfy "MiniMax"? Thanks for any clarification. Filingpro (talk) 18:23, 22 July 2016 (UTC)

NOTE: PROPOSAL TO REMOVE MINIMAX CRITERION

Summary of reasoning: Schulze returns different output than Minimax methods, while the MiniMax decision of a given player is different than a criterion for a voting system.

Will wait 3 weeks before removal.
Filingpro (talk) 07:45, 27 August 2016 (UTC)

Will not have time to return to do the removal for several months, if someone else would like to do so. Filingpro (talk) 03:27, 22 November 2016 (UTC)

Made change on template but not updating on Schulze method page. This needs to be fixed.Filingpro (talk) 18:43, 26 November 2016 (UTC)

Complete garbage

Sorry Schulze, you're completely obtuseness to include the "Tennessee example" and stubbornly stick with this obscure spiderweb map makes this method all but incomprehensible to all but the greatest autists. Sad really, as this would be an excellent method to elect single winner executive positions over IRV. And you wonder why the two round system/IRV/STV are used the world over infinitely more than your still confusing method. — Preceding unsigned comment added by 64.66.22.220 (talk) 19:09, 12 May 2016 (UTC)

As Albert Einstein said: "Make things as simple as possible, but not simpler." Markus Schulze 09:04, 13 May 2016 (UTC)

But the section beginning "An alternative, slower, way to describe the winner of the Schulze method" is vastly clearer to ordinary people - even people with, say, a PhD in physics. Sure, if you happen to already know graph theory then the system described above may be briefer. Most people do not know graph theory. The iterative process described is something anyone can follow. If it is correct (and as far as I can tell, it is), then it should be presented first.

To put it another way, it's like writing a tiny command-line utility in c, and #include-ing the whole gnu toolkit because using the data structures makes the elegance of the algorithm clearer and makes the program 1 line shorter... except, in this case, instead of including something easily acquired in a short time like the gnu toolkit, it takes a graduate-level course in math. -- Luke A Somers 2016-09-18 — Preceding unsigned comment added by 100.14.175.181 (talk) 15:07, 18 September 2016 (UTC)

A similar method called "Schulze" in an article

In this article on Medium, they use the term "Schulze" for a similar but much simpler method. They actually use the exact same example as here (starting at the third graph from the top, "Ok so here's another election..."), but they eliminate the weakest edge in the graph (E→A with strength 23), disregarding the longer but stronger path (E→D→C→B→A with strength 25). This produces a different winner. I assume they have just misunderstood what the Schulze method is, but the simplicity is alluring, so I just wanted to ask if the drawbacks of this simpler method have been assessed. 94.255.173.199 (talk) 11:01, 29 September 2018 (UTC)

In the Wikipedia article, the arrows always go from the winner to the loser of the respective pairwise contest. However, in the Medium article, the arrows always go from the loser to the winner of the respective pairwise contest. Therefore, the example in the Medium article is not the exact same example as here, it is the exact inversion of the example in the Wikipedia article. Markus Schulze 14:38, 1 October 2018 (UTC)

Something that I don't understand

The article says: "To avoid cluttering the diagram, an arrow has only been drawn from X to Y when d[X, Y] > d[Y, X] (i.e. the table cells with light green background), omitting the one in the opposite direction (the table cells with light red background)."

Why is it a legal move to ignore the opposite paths? I mean, I belive it, the article just doesn't explain it. — Preceding unsigned comment added by MainframeXYZ (talk • contribs) 19:28, 12 January 2019 (UTC)

Every pairwise win or tie (XY with d[X,Y] ≥ d[Y,X]) is stronger than every pairwise defeat (ZW with d[Z,W] < d[W,Z]).

For every pair of candidates AB, there is a path from A to B or a path from B to A that contains no pairwise defeat. This follows directly from the fact that already the link AB is a path from A to B that contains no pairwise defeat or the link BA is a path from B to A that contains no pairwise defeat.

Because of these considerations, the strength of a pairwise defeat cannot have an impact on the result of the election. Therefore, links that are pairwise defeats can be ignored. Markus Schulze 10:51, 13 January 2019 (UTC)

Schwartz-minimax explanation

I might be missing something, but it seems like the alternative implementations section could be summed up as applying minimax to the Schwartz set. Isn't this a much simpler way of explaining it? Thirsch7 (talk) 21:25, 11 February 2019 (UTC)

No, the Schulze method is not Schwartz-MinMax and the alternative implementation section doesn't claim this. Markus Schulze 10:18, 13 February 2019 (UTC)

I understand that this isn't what the alternative implementation section claims, but it seems equivalent to it. If you start with the Schwartz set and continuously remove the smallest defeats until one candidate's row is clear, the first candidate to have a clear row will be the one whose largest defeat is the smallest (the minimax winner). The fact that the Schwartz set is recalculated after each drop is irrelevant because only defeats are removed, and no candidate can be excluded from the Schwartz set after one of their defeats is removed. Maybe this alternative implementation is inaccurate or missing a step in the explanation? Thirsch7 (talk) 00:57, 14 February 2019 (UTC)

"The fact that the Schwartz set is recalculated after each drop is irrelevant because only defeats are removed, and no candidate can be excluded from the Schwartz set after one of their defeats is removed." Example: Suppose there are three alternatives A, B, C. Suppose there is a circular tie A > B > C > A. Then the Schwartz set is {A,B,C}. Suppose C > A is the weakest link. Then, when the link C > A is replaced by a pairwise tie C = A, the new Schwartz set is {A}. Markus Schulze 11:24, 17 February 2019 (UTC)