[EM] Easy River definition (also my site is back up)

[Ted Stern]

I think your questions are answered here:

https://electowiki.org/wiki/River


On Sat, Mar 9, 2024 at 8:34 PM Michael Ossipoff <email9648742 at gmail.com>
wrote:

>
>
> On Sat, Mar 9, 2024 at 15:50 Closed Limelike Curves <
> closed.limelike.curves at gmail.com> wrote:
>
>> River is actually really easy to explain:
>> 1. List all pairwise matches from biggest to smallest margin of victory.
>> 2. If a candidate loses a match, cross them out (declare them to be a
>> loser). Cross out any redundant matches that involve them (anything that
>> would make them get eliminated twice).
>> 3. Cross out any elections that would create a cycle.
>>
>
> Could that be worded as:
>
> List the defeats, one at a time, stronger ones first.
>
> But skip any defeat that cycles with already-listed defeats.
>
> …& also skip any defeat whose defeated-candidate is defeated in an
> already-listed defeat.
>
> When all defeats have been listed or skipped, elect the candidate who
> isn’t beaten in a listed defeat.
>
>>
>>
>> On Sat, Mar 9, 2024 at 2:46 PM Michael Ossipoff <email9648742 at gmail.com>
>> wrote:
>>
>>> Wow. River doesn’t need the exhaustive pairwise-count? How does its
>>> count-time compare to that of RP?
>>>
>>> I didn’t know that about River. I believed that only Sequential-Pairwise
>>> was the only exception to the need for the exhaustive pairwise-count.
>>>
>>> The exhaustive count requires, per voter, counting one pairwise-vote for
>>> each possible pair of candidates.
>>>
>>> How many votes need to be counted per voter in River?
>>>
>>> If one only cares about finding the winner, rather than an
>>> output-ranking, could the count-instruction be written more briefly?
>>>
>>> As written, it’s much too complicated for a public-proposal.
>>>
>>> Someone said that River is better at deterring burial. I disagree. It
>>> seems to me that skipping a defeat if its defeated is defeated in an
>>> already-kept defeat undermines autodeterence.
>>>
>>> Only one of the CW’s defeats is kept. That means that every Bus but one
>>> can’t have its defeat dropped, so only one Bus survives.
>>>
>>> I like it if the exhaustive pairwise-count isn’t needed, but can the
>>> count-instructions be written more briefly, if only the winner is needed?
>>>
>>> On Sat, Mar 9, 2024 at 07:02 Kevin Venzke <stepjak at yahoo.fr> wrote:
>>>
>>>> Hi Mike and everyone,
>>>>
>>>> First off, if anyone was missing my site, it is back up. I had to find
>>>> different
>>>> hosting (a bit abruptly).
>>>>
>>>> Where I was trying to link right before the site went down:
>>>> votingmethods.net/cond
>>>> works out a given (or random) scenario for Schulze, RP, or River. You
>>>> just have to
>>>> expand sections at the bottom of the result. So it could be worth a
>>>> look.
>>>>
>>>> Mike wrote:
>>>> > Is River as easy to define &. explain as RP?.
>>>>
>>>> I see I should try to write out clearly how I suggest to understand
>>>> River.
>>>>
>>>> There is no "final ranking" in River. Instead every candidate begins
>>>> "below no one"
>>>> or "subordinated to no one." This is sort of a ranking but the "trees"
>>>> we make go
>>>> only one level down: you will never be able to ascend two positions
>>>> from a given
>>>> candidate.
>>>>
>>>> 1. Initially each candidate is subordinated to no one.
>>>> 2. Consider each pairwise defeat from strongest to weakest.
>>>> 3. When you consider a defeat, ask whether the loser is subordinated to
>>>> anyone?
>>>> If so: Ignore the defeat and proceed to the next.
>>>> If not, then ask:
>>>> 4. Is the defeat winner subordinated to the defeat loser? If so, ignore
>>>> the defeat
>>>> and go to the next.
>>>> 5. Is the defeat winner subordinated to someone else? If so, the defeat
>>>> loser, along
>>>> with everyone subordinated to them, becomes subordinated to the
>>>> candidate that the
>>>> defeat winner is subordinated to.
>>>> 6. Otherwise it must be that the defeat winner is subordinated to no
>>>> one. So here
>>>> the defeat loser, along with everyone subordinated to them, becomes
>>>> subordinated to
>>>> the defeat winner.
>>>> 7. End loop. Go to the next defeat.
>>>> 8. In the end, the candidates subordinated to no one are the winners.
>>>>
>>>> Alternatively instead of talking about subordination, you can say that
>>>> each
>>>> candidate has their own "bin" and starts in their own and may move to
>>>> another.
>>>> This would allow you to merge steps 4 and 5:
>>>> "4. The defeat loser, along with everyone *in the loser's bin*, moves
>>>> to whichever
>>>> bin the defeat winner is currently located in."
>>>> And if the latter bin happens to be the loser's bin, in effect nothing
>>>> happens. We
>>>> don't need a rule saying to ignore the defeat, because the bin movement
>>>> doesn't
>>>> change anything either.
>>>>
>>>> I can understand if a reader eyeballs all that and says this looks like
>>>> a mess and
>>>> it's not clearer than RP.
>>>>
>>>> But hear me out on the *ease* of it:
>>>>
>>>> 1. If you are programming River, you never actually check for a cycle,
>>>> whether a
>>>> proposed defeat would create one. And comparing to Schulze, you never
>>>> trace a
>>>> beatpath or find its strength, or (by its other algorithm) have to find
>>>> the Schwartz
>>>> set repeatedly.
>>>> 2. If you are solving it by hand, it would be enough to have a fridge
>>>> magnet for
>>>> each candidate, start them out in imaginary bins, and push the magnets
>>>> around in a
>>>> straightforward way to track who is subordinated to whom.
>>>>
>>>> It may be possible to define RP more concisely, but it takes some work
>>>> to figure out
>>>> what it is actually saying to do to solve it.
>>>>
>>>> Hopefully the above explains it better than I have before.
>>>>
>>>> Kevin
>>>> votingmethods.net
>>>>
>>> ----
>>> Election-Methods mailing list - see https://electorama.com/em for list
>>> info
>>>
>> ----
> Election-Methods mailing list - see https://electorama.com/em for list
> info
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20240311/fa7a38b5/attachment-0001.htm>