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Rename all the election operations (#6245)
* Rename and move sp-phragmen * More renames for equalise * Update main module doc * Fix line width * Line width
This commit is contained in:
Kian Paimani
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// This file is part of Substrate.
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// Copyright (C) 2019-2020 Parity Technologies (UK) Ltd.
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// SPDX-License-Identifier: Apache-2.0
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//! Mock file for npos-elections.
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#![cfg(test)]
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use crate::{seq_phragmen, ElectionResult, Assignment, VoteWeight, ExtendedBalance};
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use sp_arithmetic::{PerThing, traits::{SaturatedConversion, Zero, One}};
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use sp_std::collections::btree_map::BTreeMap;
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use sp_runtime::assert_eq_error_rate;
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#[derive(Default, Debug)]
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pub(crate) struct _Candidate<A> {
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who: A,
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score: f64,
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approval_stake: f64,
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elected: bool,
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}
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#[derive(Default, Debug)]
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pub(crate) struct _Voter<A> {
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who: A,
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edges: Vec<_Edge<A>>,
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budget: f64,
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load: f64,
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}
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#[derive(Default, Debug)]
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pub(crate) struct _Edge<A> {
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who: A,
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load: f64,
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candidate_index: usize,
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}
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#[derive(Default, Debug, PartialEq)]
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pub(crate) struct _Support<A> {
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pub own: f64,
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pub total: f64,
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pub others: Vec<_PhragmenAssignment<A>>,
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}
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pub(crate) type _PhragmenAssignment<A> = (A, f64);
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pub(crate) type _SupportMap<A> = BTreeMap<A, _Support<A>>;
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pub(crate) type AccountId = u64;
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#[derive(Debug, Clone)]
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pub(crate) struct _PhragmenResult<A: Clone> {
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pub winners: Vec<(A, ExtendedBalance)>,
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pub assignments: Vec<(A, Vec<_PhragmenAssignment<A>>)>
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}
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pub(crate) fn auto_generate_self_voters<A: Clone>(candidates: &[A]) -> Vec<(A, Vec<A>)> {
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candidates.iter().map(|c| (c.clone(), vec![c.clone()])).collect()
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}
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pub(crate) fn elect_float<A, FS>(
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candidate_count: usize,
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minimum_candidate_count: usize,
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initial_candidates: Vec<A>,
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initial_voters: Vec<(A, Vec<A>)>,
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stake_of: FS,
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) -> Option<_PhragmenResult<A>> where
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A: Default + Ord + Copy,
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for<'r> FS: Fn(&'r A) -> VoteWeight,
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{
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let mut elected_candidates: Vec<(A, ExtendedBalance)>;
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let mut assigned: Vec<(A, Vec<_PhragmenAssignment<A>>)>;
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let mut c_idx_cache = BTreeMap::<A, usize>::new();
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let num_voters = initial_candidates.len() + initial_voters.len();
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let mut voters: Vec<_Voter<A>> = Vec::with_capacity(num_voters);
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let mut candidates = initial_candidates
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.into_iter()
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.enumerate()
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.map(|(idx, who)| {
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c_idx_cache.insert(who.clone(), idx);
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_Candidate { who, ..Default::default() }
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})
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.collect::<Vec<_Candidate<A>>>();
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if candidates.len() < minimum_candidate_count {
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return None;
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}
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voters.extend(initial_voters.into_iter().map(|(who, votes)| {
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let voter_stake = stake_of(&who) as f64;
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let mut edges: Vec<_Edge<A>> = Vec::with_capacity(votes.len());
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for v in votes {
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if let Some(idx) = c_idx_cache.get(&v) {
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candidates[*idx].approval_stake = candidates[*idx].approval_stake + voter_stake;
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edges.push(
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_Edge { who: v.clone(), candidate_index: *idx, ..Default::default() }
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);
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}
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}
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_Voter {
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who,
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edges: edges,
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budget: voter_stake,
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load: 0f64,
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}
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}));
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let to_elect = candidate_count.min(candidates.len());
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elected_candidates = Vec::with_capacity(candidate_count);
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assigned = Vec::with_capacity(candidate_count);
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for _round in 0..to_elect {
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for c in &mut candidates {
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if !c.elected {
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c.score = 1.0 / c.approval_stake;
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}
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}
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for n in &voters {
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for e in &n.edges {
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let c = &mut candidates[e.candidate_index];
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if !c.elected && !(c.approval_stake == 0f64) {
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c.score += n.budget * n.load / c.approval_stake;
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}
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}
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}
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if let Some(winner) = candidates
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.iter_mut()
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.filter(|c| !c.elected)
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.min_by(|x, y| x.score.partial_cmp(&y.score).unwrap_or(sp_std::cmp::Ordering::Equal))
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{
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winner.elected = true;
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for n in &mut voters {
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for e in &mut n.edges {
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if e.who == winner.who {
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e.load = winner.score - n.load;
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n.load = winner.score;
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}
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}
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}
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elected_candidates.push((winner.who.clone(), winner.approval_stake as ExtendedBalance));
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} else {
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break
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}
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}
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for n in &mut voters {
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let mut assignment = (n.who.clone(), vec![]);
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for e in &mut n.edges {
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if let Some(c) = elected_candidates.iter().cloned().map(|(c, _)| c).find(|c| *c == e.who) {
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if c != n.who {
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let ratio = e.load / n.load;
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assignment.1.push((e.who.clone(), ratio));
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}
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}
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}
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if assignment.1.len() > 0 {
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assigned.push(assignment);
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}
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}
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Some(_PhragmenResult {
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winners: elected_candidates,
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assignments: assigned,
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})
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}
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pub(crate) fn equalize_float<A, FS>(
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mut assignments: Vec<(A, Vec<_PhragmenAssignment<A>>)>,
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supports: &mut _SupportMap<A>,
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tolerance: f64,
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iterations: usize,
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stake_of: FS,
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) where
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for<'r> FS: Fn(&'r A) -> VoteWeight,
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A: Ord + Clone + std::fmt::Debug,
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{
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for _i in 0..iterations {
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let mut max_diff = 0.0;
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for (voter, assignment) in assignments.iter_mut() {
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let voter_budget = stake_of(&voter);
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let diff = do_equalize_float(
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voter,
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voter_budget,
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assignment,
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supports,
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tolerance,
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);
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if diff > max_diff { max_diff = diff; }
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}
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if max_diff < tolerance {
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break;
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}
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}
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}
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pub(crate) fn do_equalize_float<A>(
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voter: &A,
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budget_balance: VoteWeight,
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elected_edges: &mut Vec<_PhragmenAssignment<A>>,
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support_map: &mut _SupportMap<A>,
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tolerance: f64
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) -> f64 where
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A: Ord + Clone,
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{
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let budget = budget_balance as f64;
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if elected_edges.is_empty() { return 0.0; }
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let stake_used = elected_edges
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.iter()
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.fold(0.0, |s, e| s + e.1);
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let backed_stakes_iter = elected_edges
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.iter()
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.filter_map(|e| support_map.get(&e.0))
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.map(|e| e.total);
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let backing_backed_stake = elected_edges
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.iter()
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.filter(|e| e.1 > 0.0)
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.filter_map(|e| support_map.get(&e.0))
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.map(|e| e.total)
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.collect::<Vec<f64>>();
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let mut difference;
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if backing_backed_stake.len() > 0 {
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let max_stake = backing_backed_stake
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.iter()
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.max_by(|x, y| x.partial_cmp(&y).unwrap_or(sp_std::cmp::Ordering::Equal))
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.expect("vector with positive length will have a max; qed");
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let min_stake = backed_stakes_iter
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.min_by(|x, y| x.partial_cmp(&y).unwrap_or(sp_std::cmp::Ordering::Equal))
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.expect("iterator with positive length will have a min; qed");
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difference = max_stake - min_stake;
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difference = difference + budget - stake_used;
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if difference < tolerance {
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return difference;
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}
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} else {
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difference = budget;
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}
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// Undo updates to support
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elected_edges.iter_mut().for_each(|e| {
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if let Some(support) = support_map.get_mut(&e.0) {
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support.total = support.total - e.1;
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support.others.retain(|i_support| i_support.0 != *voter);
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}
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e.1 = 0.0;
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});
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elected_edges.sort_unstable_by(|x, y|
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support_map.get(&x.0)
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.and_then(|x| support_map.get(&y.0).and_then(|y| x.total.partial_cmp(&y.total)))
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.unwrap_or(sp_std::cmp::Ordering::Equal)
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);
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let mut cumulative_stake = 0.0;
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let mut last_index = elected_edges.len() - 1;
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elected_edges.iter_mut().enumerate().for_each(|(idx, e)| {
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if let Some(support) = support_map.get_mut(&e.0) {
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let stake = support.total;
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let stake_mul = stake * (idx as f64);
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let stake_sub = stake_mul - cumulative_stake;
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if stake_sub > budget {
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last_index = idx.checked_sub(1).unwrap_or(0);
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return
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}
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cumulative_stake = cumulative_stake + stake;
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}
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});
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let last_stake = elected_edges[last_index].1;
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let split_ways = last_index + 1;
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let excess = budget + cumulative_stake - last_stake * (split_ways as f64);
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elected_edges.iter_mut().take(split_ways).for_each(|e| {
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if let Some(support) = support_map.get_mut(&e.0) {
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e.1 = excess / (split_ways as f64) + last_stake - support.total;
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support.total = support.total + e.1;
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support.others.push((voter.clone(), e.1));
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}
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});
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difference
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}
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pub(crate) fn create_stake_of(stakes: &[(AccountId, VoteWeight)])
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-> Box<dyn Fn(&AccountId) -> VoteWeight>
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{
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let mut storage = BTreeMap::<AccountId, VoteWeight>::new();
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stakes.iter().for_each(|s| { storage.insert(s.0, s.1); });
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let stake_of = move |who: &AccountId| -> VoteWeight { storage.get(who).unwrap().to_owned() };
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Box::new(stake_of)
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}
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pub fn check_assignments_sum<T: PerThing>(assignments: Vec<Assignment<AccountId, T>>) {
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for Assignment { distribution, .. } in assignments {
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let mut sum: u128 = Zero::zero();
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distribution.iter().for_each(|(_, p)| sum += p.deconstruct().saturated_into());
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assert_eq_error_rate!(sum, T::ACCURACY.saturated_into(), 1);
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}
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}
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pub(crate) fn run_and_compare<Output: PerThing>(
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candidates: Vec<AccountId>,
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voters: Vec<(AccountId, Vec<AccountId>)>,
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stake_of: &Box<dyn Fn(&AccountId) -> VoteWeight>,
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to_elect: usize,
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min_to_elect: usize,
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) {
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// run fixed point code.
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let ElectionResult { winners, assignments } = seq_phragmen::<_, Output>(
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to_elect,
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min_to_elect,
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candidates.clone(),
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voters.iter().map(|(ref v, ref vs)| (v.clone(), stake_of(v), vs.clone())).collect::<Vec<_>>(),
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).unwrap();
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// run float poc code.
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let truth_value = elect_float(
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to_elect,
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min_to_elect,
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candidates,
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voters,
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&stake_of,
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).unwrap();
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assert_eq!(winners.iter().map(|(x, _)| x).collect::<Vec<_>>(), truth_value.winners.iter().map(|(x, _)| x).collect::<Vec<_>>());
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for Assignment { who, distribution } in assignments.clone() {
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if let Some(float_assignments) = truth_value.assignments.iter().find(|x| x.0 == who) {
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for (candidate, per_thingy) in distribution {
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if let Some(float_assignment) = float_assignments.1.iter().find(|x| x.0 == candidate ) {
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assert_eq_error_rate!(
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Output::from_fraction(float_assignment.1).deconstruct(),
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per_thingy.deconstruct(),
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Output::Inner::one(),
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);
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} else {
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panic!("candidate mismatch. This should never happen.")
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}
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}
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} else {
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panic!("nominator mismatch. This should never happen.")
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}
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}
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check_assignments_sum(assignments);
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}
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pub(crate) fn build_support_map_float<FS>(
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result: &mut _PhragmenResult<AccountId>,
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stake_of: FS,
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) -> _SupportMap<AccountId>
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where for<'r> FS: Fn(&'r AccountId) -> VoteWeight
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{
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let mut supports = <_SupportMap<AccountId>>::new();
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result.winners
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.iter()
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.map(|(e, _)| (e, stake_of(e) as f64))
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.for_each(|(e, s)| {
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let item = _Support { own: s, total: s, ..Default::default() };
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supports.insert(e.clone(), item);
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});
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for (n, assignment) in result.assignments.iter_mut() {
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for (c, r) in assignment.iter_mut() {
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let nominator_stake = stake_of(n) as f64;
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let other_stake = nominator_stake * *r;
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if let Some(support) = supports.get_mut(c) {
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support.total = support.total + other_stake;
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support.others.push((n.clone(), other_stake));
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}
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*r = other_stake;
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}
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}
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supports
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}
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