Gonçalo Pestana
b793666ca5
* Abstracts elections-phragmen pallet to use NposSolver * Update frame/elections-phragmen/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Update frame/elections-phragmen/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * changes the name of the pallet; adds changelog * update changelog * Adds weight testing * Adds log macro_rules * renames elections-phragment dir to elections * weights rename * fixes typo in cargo toml * pre/post solve weight scafolding * refactor do_post_election * refactors into pre and post election solve for independent benchmarking * deconstructs PreElectionResults struct * updates benchmarking pre and post election solve; mock weights * Update frame/elections/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Update frame/elections/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * addresses PR comments * adds pre_solve and post_sove weights * Adds comments on election pallet id param name change * ".git/.scripts/bench-bot.sh" pallet dev pallet_elections * Finishes pre-post solve weights * Update frame/elections/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Update frame/elections/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Addresses PR comments: no panic in on_init path; nits * Fixes node build * Implements approval voting to use as a `NposSolver` (#13367) * Implements the approval voting methods in sp_npos_elections * fmt * remove unecessary file * comment clarification * re-run weights * fix typo * updates MaxVoters in tests for integrity_tests to pass * Refactors election provider support benchmarks outside its own crate (#13431) * Refactors election provider support benchmarks outside its own crate --------- Co-authored-by: command-bot <> --------- Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> Co-authored-by: parity-processbot <> Co-authored-by: Ross Bulat <ross@parity.io>
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