pallet_elections_phragmen/

benchmarking.rs

// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Elections-Phragmen pallet benchmarking.

#![cfg(feature = "runtime-benchmarks")]

use frame_benchmarking::v2::*;
use frame_support::{dispatch::DispatchResultWithPostInfo, traits::OnInitialize};
use frame_system::RawOrigin;

#[cfg(test)]
use crate::tests::MEMBERS;
use crate::*;

const BALANCE_FACTOR: u32 = 250;

// grab new account with infinite balance.
fn endowed_account<T: Config>(name: &'static str, index: u32) -> T::AccountId {
	let account: T::AccountId = account(name, index, 0);
	// Fund each account with at-least their stake but still a sane amount as to not mess up
	// the vote calculation.
	let amount = default_stake::<T>(T::MaxVoters::get()) * BalanceOf::<T>::from(BALANCE_FACTOR);
	let _ = T::Currency::make_free_balance_be(&account, amount);
	// Important to increase the total issuance since `T::CurrencyToVote` will need it to be sane
	// for phragmen to work.
	let _ = T::Currency::issue(amount);

	account
}

// Account to lookup type of system trait.
fn as_lookup<T: Config>(account: T::AccountId) -> AccountIdLookupOf<T> {
	T::Lookup::unlookup(account)
}

// Get a reasonable amount of stake based on the execution trait's configuration.
fn default_stake<T: Config>(num_votes: u32) -> BalanceOf<T> {
	let min = T::Currency::minimum_balance();
	Pallet::<T>::deposit_of(num_votes as usize).max(min)
}

// Get the current number of candidates.
fn candidate_count<T: Config>() -> u32 {
	Candidates::<T>::decode_len().unwrap_or(0usize) as u32
}

// Add `c` new candidates.
fn submit_candidates<T: Config>(
	c: u32,
	prefix: &'static str,
) -> Result<Vec<T::AccountId>, &'static str> {
	(0..c)
		.map(|i| {
			let account = endowed_account::<T>(prefix, i);
			Pallet::<T>::submit_candidacy(
				RawOrigin::Signed(account.clone()).into(),
				candidate_count::<T>(),
			)
			.map_err(|_| "failed to submit candidacy")?;
			Ok(account)
		})
		.collect::<Result<_, _>>()
}

// Add `c` new candidates with self vote.
fn submit_candidates_with_self_vote<T: Config>(
	c: u32,
	prefix: &'static str,
) -> Result<Vec<T::AccountId>, &'static str> {
	let candidates = submit_candidates::<T>(c, prefix)?;
	let stake = default_stake::<T>(c);
	candidates
		.iter()
		.try_for_each(|c| submit_voter::<T>(c.clone(), vec![c.clone()], stake).map(|_| ()))?;
	Ok(candidates)
}

// Submit one voter.
fn submit_voter<T: Config>(
	caller: T::AccountId,
	votes: Vec<T::AccountId>,
	stake: BalanceOf<T>,
) -> DispatchResultWithPostInfo {
	Pallet::<T>::vote(RawOrigin::Signed(caller).into(), votes, stake)
}

// Create `num_voter` voters who randomly vote for at most `votes` of `all_candidates` if
// available.
fn distribute_voters<T: Config>(
	mut all_candidates: Vec<T::AccountId>,
	num_voters: u32,
	votes: usize,
) -> Result<(), &'static str> {
	let stake = default_stake::<T>(num_voters);
	for i in 0..num_voters {
		// to ensure that votes are different
		all_candidates.rotate_left(1);
		let votes = all_candidates.iter().cloned().take(votes).collect::<Vec<_>>();
		let voter = endowed_account::<T>("voter", i);
		submit_voter::<T>(voter, votes, stake)?;
	}
	Ok(())
}

// Fill the seats of members and runners-up up until `m`. Note that this might include either only
// members, or members and runners-up.
fn fill_seats_up_to<T: Config>(m: u32) -> Result<Vec<T::AccountId>, &'static str> {
	submit_candidates_with_self_vote::<T>(m, "fill_seats_up_to")?;
	assert_eq!(Candidates::<T>::get().len() as u32, m, "wrong number of candidates.");
	Pallet::<T>::do_phragmen();
	assert_eq!(Candidates::<T>::get().len(), 0, "some candidates remaining.");
	assert_eq!(
		Members::<T>::get().len() + RunnersUp::<T>::get().len(),
		m as usize,
		"wrong number of members and runners-up",
	);
	Ok(Members::<T>::get()
		.into_iter()
		.map(|m| m.who)
		.chain(RunnersUp::<T>::get().into_iter().map(|r| r.who))
		.collect())
}

// Removes all the storage items to reverse any genesis state.
fn clean<T: Config>() {
	Members::<T>::kill();
	Candidates::<T>::kill();
	RunnersUp::<T>::kill();
	#[allow(deprecated)]
	Voting::<T>::remove_all(None);
}

#[benchmarks]
mod benchmarks {
	use super::*;

	// -- Signed ones
	#[benchmark]
	fn vote_equal(v: Linear<1, { T::MaxVotesPerVoter::get() }>) -> Result<(), BenchmarkError> {
		clean::<T>();

		// create a bunch of candidates.
		let all_candidates = submit_candidates::<T>(v, "candidates")?;

		let caller = endowed_account::<T>("caller", 0);
		let stake = default_stake::<T>(v);

		// Original votes.
		let mut votes = all_candidates;
		submit_voter::<T>(caller.clone(), votes.clone(), stake)?;

		// New votes.
		votes.rotate_left(1);

		whitelist!(caller);

		#[extrinsic_call]
		vote(RawOrigin::Signed(caller), votes, stake);

		Ok(())
	}

	#[benchmark]
	fn vote_more(v: Linear<2, { T::MaxVotesPerVoter::get() }>) -> Result<(), BenchmarkError> {
		clean::<T>();

		// Create a bunch of candidates.
		let all_candidates = submit_candidates::<T>(v, "candidates")?;

		let caller = endowed_account::<T>("caller", 0);
		// Multiply the stake with 10 since we want to be able to divide it by 10 again.
		let stake = default_stake::<T>(v) * BalanceOf::<T>::from(10_u32);

		// Original votes.
		let mut votes = all_candidates.iter().skip(1).cloned().collect::<Vec<_>>();
		submit_voter::<T>(caller.clone(), votes.clone(), stake / BalanceOf::<T>::from(10_u32))?;

		// New votes.
		votes = all_candidates;
		assert!(votes.len() > Voting::<T>::get(caller.clone()).votes.len());

		whitelist!(caller);

		#[extrinsic_call]
		vote(RawOrigin::Signed(caller), votes, stake / BalanceOf::<T>::from(10_u32));

		Ok(())
	}

	#[benchmark]
	fn vote_less(v: Linear<2, { T::MaxVotesPerVoter::get() }>) -> Result<(), BenchmarkError> {
		clean::<T>();

		// Create a bunch of candidates.
		let all_candidates = submit_candidates::<T>(v, "candidates")?;

		let caller = endowed_account::<T>("caller", 0);
		let stake = default_stake::<T>(v);

		// Original votes.
		let mut votes = all_candidates;
		submit_voter::<T>(caller.clone(), votes.clone(), stake)?;

		// New votes.
		votes = votes.into_iter().skip(1).collect::<Vec<_>>();
		assert!(votes.len() < Voting::<T>::get(caller.clone()).votes.len());

		whitelist!(caller);

		#[extrinsic_call]
		vote(RawOrigin::Signed(caller), votes, stake);

		Ok(())
	}

	#[benchmark]
	fn remove_voter() -> Result<(), BenchmarkError> {
		// We fix the number of voted candidates to max.
		let v = T::MaxVotesPerVoter::get();
		clean::<T>();

		// Create a bunch of candidates.
		let all_candidates = submit_candidates::<T>(v, "candidates")?;

		let caller = endowed_account::<T>("caller", 0);

		let stake = default_stake::<T>(v);
		submit_voter::<T>(caller.clone(), all_candidates, stake)?;

		whitelist!(caller);

		#[extrinsic_call]
		_(RawOrigin::Signed(caller));

		Ok(())
	}

	#[benchmark]
	fn submit_candidacy(
		// Number of already existing candidates.
		c: Linear<1, { T::MaxCandidates::get() }>,
	) -> Result<(), BenchmarkError> {
		// We fix the number of members to the number of desired members and runners-up.
		// We'll be in this state almost always.
		let m = T::DesiredMembers::get() + T::DesiredRunnersUp::get();

		clean::<T>();

		// Create `m` members and runners combined.
		fill_seats_up_to::<T>(m)?;

		// Create previous candidates.
		submit_candidates::<T>(c, "candidates")?;

		// We assume worse case that: extrinsic is successful and candidate is not duplicate.
		let candidate_account = endowed_account::<T>("caller", 0);
		whitelist!(candidate_account);

		#[extrinsic_call]
		_(RawOrigin::Signed(candidate_account), candidate_count::<T>());

		// Reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	#[benchmark]
	fn renounce_candidacy_candidate(
		// This will check members, runners-up and candidate for removal.
		// Members and runners-up are limited by the runtime bound, nonetheless we fill them by
		// `m`.
		// Number of already existing candidates.
		c: Linear<1, { T::MaxCandidates::get() }>,
	) -> Result<(), BenchmarkError> {
		// We fix the number of members to the number of desired members and runners-up.
		// We'll be in this state almost always.
		let m = T::DesiredMembers::get() + T::DesiredRunnersUp::get();

		clean::<T>();

		// Create `m` members and runners combined.
		fill_seats_up_to::<T>(m)?;
		let all_candidates = submit_candidates::<T>(c, "caller")?;

		let bailing = all_candidates[0].clone(); // Should be ("caller", 0)
		let count = candidate_count::<T>();
		whitelist!(bailing);

		#[extrinsic_call]
		renounce_candidacy(RawOrigin::Signed(bailing), Renouncing::Candidate(count));

		// Reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	#[benchmark]
	fn renounce_candidacy_members() -> Result<(), BenchmarkError> {
		// Removing members and runners will be cheaper than a candidate.
		// We fix the number of members to when members and runners-up to the desired.
		// We'll be in this state almost always.
		let m = T::DesiredMembers::get() + T::DesiredRunnersUp::get();
		clean::<T>();

		// Create `m` members and runners combined.
		let members_and_runners_up = fill_seats_up_to::<T>(m)?;

		let bailing = members_and_runners_up[0].clone();
		assert!(Pallet::<T>::is_member(&bailing));

		whitelist!(bailing);

		#[extrinsic_call]
		renounce_candidacy(RawOrigin::Signed(bailing.clone()), Renouncing::Member);

		// Reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	#[benchmark]
	fn renounce_candidacy_runners_up() -> Result<(), BenchmarkError> {
		// Removing members and runners will be cheaper than a candidate.
		// We fix the number of members to when members and runners-up to the desired.
		// We'll be in this state almost always.
		let m = T::DesiredMembers::get() + T::DesiredRunnersUp::get();
		clean::<T>();

		// Create `m` members and runners combined.
		let members_and_runners_up = fill_seats_up_to::<T>(m)?;

		let bailing = members_and_runners_up[T::DesiredMembers::get() as usize + 1].clone();
		assert!(Pallet::<T>::is_runner_up(&bailing));

		whitelist!(bailing);

		#[extrinsic_call]
		renounce_candidacy(RawOrigin::Signed(bailing.clone()), Renouncing::RunnerUp);

		// Reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	// We use the max block weight for this extrinsic for now. See below.
	#[benchmark]
	fn remove_member_without_replacement() -> Result<(), BenchmarkError> {
		#[block]
		{
			Err(BenchmarkError::Override(BenchmarkResult::from_weight(
				T::BlockWeights::get().max_block,
			)))?;
		}

		Ok(())
	}

	#[benchmark]
	fn remove_member_with_replacement() -> Result<(), BenchmarkError> {
		// Easy case.
		// We have a runner up.
		// Nothing will have that much of an impact.
		// `m` will be number of members and runners.
		// There is always at least one runner.
		let m = T::DesiredMembers::get() + T::DesiredRunnersUp::get();
		clean::<T>();

		fill_seats_up_to::<T>(m)?;
		let removing = as_lookup::<T>(Pallet::<T>::members_ids()[0].clone());

		#[extrinsic_call]
		remove_member(RawOrigin::Root, removing, true, false);

		// Must still have enough members.
		assert_eq!(Members::<T>::get().len() as u32, T::DesiredMembers::get());

		// Reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	#[benchmark]
	fn clean_defunct_voters(
		// Total number of voters.
		v: Linear<{ T::MaxVoters::get() / 2 }, { T::MaxVoters::get() }>,
		// Those that are defunct and need removal.
		d: Linear<0, { T::MaxVoters::get() / 2 }>,
	) -> Result<(), BenchmarkError> {
		// Remove any previous stuff.
		clean::<T>();

		let all_candidates = submit_candidates::<T>(T::MaxCandidates::get(), "candidates")?;
		distribute_voters::<T>(all_candidates, v, T::MaxVotesPerVoter::get() as usize)?;

		// All candidates leave.
		Candidates::<T>::kill();

		// Now everyone is defunct.
		assert!(Voting::<T>::iter().all(|(_, v)| Pallet::<T>::is_defunct_voter(&v.votes)));
		assert_eq!(Voting::<T>::iter().count() as u32, v);

		#[extrinsic_call]
		_(RawOrigin::Root, v, d);

		assert_eq!(Voting::<T>::iter().count() as u32, v - d);

		Ok(())
	}

	#[benchmark]
	fn election_phragmen(
		// This is just to focus on phragmen in the context of this module.
		// We always select 20 members, this is hard-coded in the runtime and cannot be trivially
		// changed at this stage. Yet, change the number of voters, candidates and edge per voter
		// to see the impact. Note that we give all candidates a self vote to make sure they are
		// all considered.
		c: Linear<1, { T::MaxCandidates::get() }>,
		v: Linear<1, { T::MaxVoters::get() }>,
		e: Linear<{ T::MaxVoters::get() }, { T::MaxVoters::get() * T::MaxVotesPerVoter::get() }>,
	) -> Result<(), BenchmarkError> {
		clean::<T>();

		// So we have a situation with `v` and `e`.
		// We want `e` to basically always be in the range of
		// `e -> e * T::MaxVotesPerVoter::get()`, but we cannot express that now with the
		// benchmarks. So what we do is: when `c` is being iterated, `v`, and `e` are max and
		// fine. When `v` is being iterated, `e` is being set to max and this is a problem.
		// In these cases, we cap `e` to a lower value, namely `v * T::MaxVotesPerVoter::get()`.
		// When `e` is being iterated, `v` is at max, and again fine.
		// All in all, `votes_per_voter` can never be more than `T::MaxVotesPerVoter::get()`.
		// Note that this might cause `v` to be an overestimate.
		let votes_per_voter = (e / v).min(T::MaxVotesPerVoter::get());

		let all_candidates = submit_candidates_with_self_vote::<T>(c, "candidates")?;
		distribute_voters::<T>(all_candidates, v.saturating_sub(c), votes_per_voter as usize)?;

		#[block]
		{
			Pallet::<T>::on_initialize(T::TermDuration::get());
		}

		assert_eq!(Members::<T>::get().len() as u32, T::DesiredMembers::get().min(c));
		assert_eq!(
			RunnersUp::<T>::get().len() as u32,
			T::DesiredRunnersUp::get().min(c.saturating_sub(T::DesiredMembers::get())),
		);

		// reset members in between benchmark tests.
		#[cfg(test)]
		MEMBERS.with(|m| *m.borrow_mut() = vec![]);

		Ok(())
	}

	impl_benchmark_test_suite! {
		Pallet,
		tests::ExtBuilder::default().desired_members(13).desired_runners_up(7),
		tests::Test,
		exec_name = build_and_execute,
	}
}