<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px"><div id="yui_3_16_0_1_1443699685883_16751"><span>Hi Marijn,</span></div><div id="yui_3_16_0_1_1443699685883_16750"><span><br></span></div><div id="yui_3_16_0_1_1443699685883_16749"><span>Yes, a few thoughts:</span></div><div id="yui_3_16_0_1_1443699685883_16748"><span id="yui_3_16_0_1_1443699685883_16747">1. The path tracing (propagation of votes through paths) may seem odd, and it does create problems if you want to create guarantees about the effect of a given ballot (like LNHarm or FBC). But path tracing can provide a useful framework for resolving clone situations or Condorcet cycles. I'd note also that the problem of "voting A>B can help C" is a problem common to many or most election methods.</span></div><div id="yui_3_16_0_1_1443699685883_16746"><span id="yui_3_16_0_1_1443699685883_16745">2. Regarding sensitivity to a small change in votes: I would suggest that this is true even with a two-way FPP election: a contest's win vs. loss is the most important thing, and considering the strength of the win at all is a novelty. But it's an interesting question, whether the single-direction flow of votes creates more tactical voting opportunities.</span></div><div dir="ltr" id="yui_3_16_0_1_1443699685883_16744"><span id="yui_3_16_0_1_1443699685883_16743">3. I call Schulze with votes flowing in both directions "Schulze(pairwise opposition)." The results can be less decisive. For example, suppose that candidate A has 45% of the vote (bullet votes, no lower preferences), and the rest of the votes are some combination of B, C, B>C, and C>B votes. Say there is an A>C>B>A cycle. It's likely that B and C will tie for the win because each received their greatest opposition from A. Whatever tiebreaker rule is used, if it elects C, and C has fewer preferences in total than A's 45% in first preferences, that would violate the Plurality criterion. Some of us would find that to be a bad outcome (i.e. hard to defend), so you may want to consider it.</span></div><div dir="ltr" id="yui_3_16_0_1_1443699685883_16810"><span><br></span></div><div dir="ltr" id="yui_3_16_0_1_1443699685883_16755"><span>Kevin</span></div><div id="yui_3_16_0_1_1443699685883_16742"><span><br></span></div><br> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12px;" id="yui_3_16_0_1_1443699685883_15947"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_1_1443699685883_15946"> <div dir="ltr" id="yui_3_16_0_1_1443699685883_15945"> <hr size="1"> <font size="2" face="Arial" id="yui_3_16_0_1_1443699685883_15944"> <b><span style="font-weight:bold;">De :</span></b> Marijn Stollenga <m.stollenga@gmail.com><br> <b><span style="font-weight: bold;">À :</span></b> Kevin Venzke <stepjak@yahoo.fr>; "election-methods@lists.electorama.com" <election-methods@lists.electorama.com> <br> <b><span style="font-weight: bold;">Envoyé le :</span></b> Jeudi 1 octobre 2015 4h21<br> <b><span style="font-weight: bold;">Objet :</span></b> Re: [EM] Voting Benchmark<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_1_1443699685883_15948"><br><div id="yiv6400222180"><div id="yui_3_16_0_1_1443699685883_15950">
<div class="yiv6400222180moz-cite-prefix" id="yui_3_16_0_1_1443699685883_15949">Yes, actually my main motivation was
the strange properties in Schulze that I didn't like. <br clear="none">
Firstly, the propagation of votes through beaten path sounds
interesting, but it is also pretty strange. By voting a dominance
of A over B, you might end up voting for C if some large other
group votes C over A a lot, even if you don't like C at all. This
leads to some complex tactical voting.<br clear="none">
<br clear="none">
Secondly, the votes only flow if A over B has more votes than B
over A say. On first sight this sounds good but introduces a
sensitivity in the method that can completely flip results with a
small change of votes, also leading to possible loss of votes and
tactical voting. Why can't votes simply flow both directions? In
my implementation I tried it and it still led to dominant results
in my experiments, but I guess it's needed for certain properties?<br clear="none">
<br clear="none">
Any thoughts?<br clear="none">
<br clear="none">
Marijn<br clear="none">
<br clear="none">
On 30/09/15 14:40, Kevin Venzke wrote:<br clear="none">
</div>
<div class="qtdSeparateBR"><br><br></div><div class="yiv6400222180yqt0931285326" id="yiv6400222180yqt97236"><blockquote type="cite">
<div style="color:#000;background-color:#fff;font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;">
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2747"><span>Hi Marijn,</span></div>
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2746"><span><br clear="none">
</span></div>
<div><span>I think you might start with the criteria that
motivated Schulze, or criteria that differentiate popular
methods.</span></div>
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2745"><span><br clear="none">
</span></div>
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2744"><span>For instance:</span></div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2743"><span>Schulze:
clone independence, monotonicity (mono-raise), Condorcet,
Schwartz</span></div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720"><span id="yiv6400222180yui_3_16_0_1_1443615021298_3009">IRV: clone
independence, later-no-harm, later-no-help</span></div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720">Approval:
participation, favorite betrayal (FBC)</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720"><br clear="none">
</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720">Unfortunately
it's not necessarily straightforward to demonstrate that a new
method satisfies or doesn't satisfy some criterion.</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720"><br clear="none">
</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720">Some of us
have simulations to attempt to gauge the incentives to use
specific strategies (e.g. compromise, truncation, burial). But
since simulations are based on the programmer's assumptions,
nothing is standardized.</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720"><br clear="none">
</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720">My hunch
(based on my own experiments from 10+ years ago) is that if
Schulze is your original inspiration or standard, and you make
your own rank method, you may make something that gives
similar results to Schulze, but most likely it won't satisfy
all of Schulze's technical criteria.</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720"><br clear="none">
</div>
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2720">Kevin</div>
<br clear="none">
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2636" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:12px;">
<div id="yiv6400222180yui_3_16_0_1_1443615021298_2635" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;">
<div dir="ltr" id="yiv6400222180yui_3_16_0_1_1443615021298_2634">
<hr id="yiv6400222180yui_3_16_0_1_1443615021298_3043" size="1"> <font id="yiv6400222180yui_3_16_0_1_1443615021298_2633" face="Arial" size="2"> <b><span style="font-weight:bold;">De :</span></b>
Marijn Stollenga <a rel="nofollow" shape="rect" class="yiv6400222180moz-txt-link-rfc2396E" ymailto="mailto:m.stollenga@gmail.com" target="_blank" href="mailto:m.stollenga@gmail.com"><m.stollenga@gmail.com></a><br clear="none">
<b><span style="font-weight:bold;">À :</span></b>
<a rel="nofollow" shape="rect" class="yiv6400222180moz-txt-link-rfc2396E" ymailto="mailto:election-methods@lists.electorama.com" target="_blank" href="mailto:election-methods@lists.electorama.com">"election-methods@lists.electorama.com"</a>
<a rel="nofollow" shape="rect" class="yiv6400222180moz-txt-link-rfc2396E" ymailto="mailto:election-methods@lists.electorama.com" target="_blank" href="mailto:election-methods@lists.electorama.com"><election-methods@lists.electorama.com></a> <br clear="none">
<b><span style="font-weight:bold;">Envoyé le :</span></b>
Mercredi 30 septembre 2015 4h12<br clear="none">
<b><span style="font-weight:bold;">Objet :</span></b>
[EM] Voting Benchmark<br clear="none">
</font> </div>
<div class="yiv6400222180y_msg_container" id="yiv6400222180yui_3_16_0_1_1443615021298_3044"><br clear="none">
Hello,<br clear="none">
<br clear="none">
I am implementing a new election method, after initially
playing with <br clear="none">
Schulze voting. In the process I really want to compare my
method to <br clear="none">
Schulze and other methods according to several types of
quality. Is <br clear="none">
there a good benchmark currently, that I can start from?<br clear="none">
<br clear="none">
Marijn<br clear="none">
<br clear="none">
----<br clear="none">
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info<br clear="none">
<br clear="none">
<br clear="none">
</div>
</div>
</div>
</div>
</blockquote></div>
<br clear="none">
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