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

[Closed Limelike Curves]

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.



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
>>
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