Ankan
657d99202c
* bounding election provider with kian * multi phase implement bounded election provider * election provider blanket implementation * staking compiles * fix test for election provider support * fmt * fixing epmp tests, does not compile yet * fix epmp tests * fix staking tests * fmt * fix runtime tests * fmt * remove outdated wip tags * add enum error * sort and truncate supports * comment * error when unsupported number of election winners * compiling wip after kian's suggestions * fix TODOs * remove,fix tags * ensure validator count does not exceed maxwinners * clean up * some more clean up and todos * handle too many winners * rename parameter for mock * todo * add sort and truncate rule if there are too many winners * fmt * fail, not swallow emergency result bound not met * remove too many winners resolution as it can be guaranteed to be bounded * fix benchmark * give MaxWinners more contextual name * make ready solution generic over T * kian feedback * fix stuff * Kian's way of solvign this * comment fix * fix compile * remove use of BoundedExecution * fmt * comment out failing integrity test * cap validator count increment to max winners * dont panic * add test for bad data provider * Update frame/staking/src/pallet/impls.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * fix namespace conflict and add test for onchain max winners less than desired targets * defensive unwrap * early convert to bounded vec * fix syntax * fmt * fix doc * fix rustdoc * fmt * fix maxwinner count for benchmarking * add instant election for noelection * fmt * fix compile * pr feedbacks * always error at validator count exceeding max winners * add useful error message * pr comments * import fix * add checked_desired_targets * fmt * fmt * fix rust doc Co-authored-by: parity-processbot <> Co-authored-by: kianenigma <kian@parity.io> Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
A set of election algorithms to be used with a substrate runtime, typically within the staking sub-system. Notable implementation include:
- [
seq_phragmen]: Implements the Phragmén Sequential Method. An un-ranked, relatively fast election method that ensures PJR, but does not provide a constant factor approximation of the maximin problem. - [
phragmms]: Implements a hybrid approach inspired by Phragmén which is executed faster but it can achieve a constant factor approximation of the maximin problem, similar to that of the MMS algorithm. - [
balance_solution]: Implements the star balancing algorithm. This iterative process can push a solution toward being morebalanced, which in turn can increase its score.
Terminology
This crate uses context-independent words, not to be confused with staking. This is because the election algorithms of this crate, while designed for staking, can be used in other contexts as well.
Voter: The entity casting some votes to a number of Targets. This is the same as Nominator
in the context of staking. Target: The entities eligible to be voted upon. This is the same as
Validator in the context of staking. Edge: A mapping from a Voter to a Target.
The goal of an election algorithm is to provide an ElectionResult. A data composed of:
winners: A flat list of identifiers belonging to those who have won the election, usually ordered in some meaningful way. They are zipped with their total backing stake.assignment: A mapping from each voter to their winner-only targets, zipped with a ration denoting the amount of support given to that particular target.
// the winners.
let winners = vec![(1, 100), (2, 50)];
let assignments = vec![
// A voter, giving equal backing to both 1 and 2.
Assignment {
who: 10,
distribution: vec![(1, Perbill::from_percent(50)), (2, Perbill::from_percent(50))],
},
// A voter, Only backing 1.
Assignment { who: 20, distribution: vec![(1, Perbill::from_percent(100))] },
];
// the combination of the two makes the election result.
let election_result = ElectionResult { winners, assignments };
The Assignment field of the election result is voter-major, i.e. it is from the perspective of
the voter. The struct that represents the opposite is called a Support. This struct is usually
accessed in a map-like manner, i.e. keyed by voters, therefore it is stored as a mapping called
SupportMap.
Moreover, the support is built from absolute backing values, not ratios like the example above.
A struct similar to Assignment that has stake value instead of ratios is called an
StakedAssignment.
More information can be found at: https://arxiv.org/abs/2004.12990
License: Apache-2.0