Decouple Staking and Election - Part 2 Unsigned Phase (#7909)

* Base features and traits.

* pallet and unsigned phase

* Undo bad formattings.

* some formatting cleanup.

* Small self-cleanup.

* Make it all build

* self-review

* Some doc tests.

* Some changes from other PR

* Fix session test

* Update Cargo.lock

* Update frame/election-provider-multi-phase/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Some review comments

* Rename + make encode/decode

* Do an assert as well, just in case.

* Fix build

* Update frame/election-provider-multi-phase/src/unsigned.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Las comment

* fix staking fuzzer.

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Add one last layer of feasibility check as well.

* Last fixes to benchmarks

* Some more docs.

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_election_provider_multi_phase --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/election-provider-multi-phase/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Some nits

* cargo run --release --features=runtime-benchmarks --manifest-path=bin/node/cli/Cargo.toml -- benchmark --chain=dev --steps=50 --repeat=20 --pallet=pallet_staking --extrinsic=* --execution=wasm --wasm-execution=compiled --heap-pages=4096 --output=./frame/staking/src/weights.rs --template=./.maintain/frame-weight-template.hbs

* Fix doc

* Mkae ci green

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Parity Benchmarking Bot <admin@parity.io>

substrate/frame/election-provider-multi-phase/src/helpers.rs

@@ -0,0 +1,159 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020 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.
+
+//! Some helper functions/macros for this crate.
+
+use super::{Config, VoteWeight, CompactVoterIndexOf, CompactTargetIndexOf};
+use sp_std::{collections::btree_map::BTreeMap, convert::TryInto, boxed::Box, prelude::*};
+
+#[macro_export]
+macro_rules! log {
+	($level:tt, $patter:expr $(, $values:expr)* $(,)?) => {
+		frame_support::debug::$level!(
+			target: $crate::LOG_TARGET,
+			concat!("🗳 ", $patter) $(, $values)*
+		)
+	};
+}
+
+/// Generate a btree-map cache of the voters and their indices.
+///
+/// This can be used to efficiently build index getter closures.
+pub fn generate_voter_cache<T: Config>(
+	snapshot: &Vec<(T::AccountId, VoteWeight, Vec<T::AccountId>)>,
+) -> BTreeMap<T::AccountId, usize> {
+	let mut cache: BTreeMap<T::AccountId, usize> = BTreeMap::new();
+	snapshot.iter().enumerate().for_each(|(i, (x, _, _))| {
+		let _existed = cache.insert(x.clone(), i);
+		// if a duplicate exists, we only consider the last one. Defensive only, should never
+		// happen.
+		debug_assert!(_existed.is_none());
+	});
+
+	cache
+}
+
+/// Create a function the returns the index a voter in the snapshot.
+///
+/// The returning index type is the same as the one defined in [`T::CompactSolution::Voter`].
+///
+/// ## Warning
+///
+/// The snapshot must be the same is the one used to create `cache`.
+pub fn voter_index_fn<T: Config>(
+	cache: &BTreeMap<T::AccountId, usize>,
+) -> Box<dyn Fn(&T::AccountId) -> Option<CompactVoterIndexOf<T>> + '_> {
+	Box::new(move |who| {
+		cache.get(who).and_then(|i| <usize as TryInto<CompactVoterIndexOf<T>>>::try_into(*i).ok())
+	})
+}
+
+/// Same as [`voter_index_fn`], but the returning index is converted into usize, if possible.
+///
+/// ## Warning
+///
+/// The snapshot must be the same is the one used to create `cache`.
+pub fn voter_index_fn_usize<T: Config>(
+	cache: &BTreeMap<T::AccountId, usize>,
+) -> Box<dyn Fn(&T::AccountId) -> Option<usize> + '_> {
+	Box::new(move |who| cache.get(who).cloned())
+}
+
+/// A non-optimized, linear version of [`voter_index_fn`] that does not need a cache and does a
+/// linear search.
+///
+/// ## Warning
+///
+/// Not meant to be used in production.
+pub fn voter_index_fn_linear<T: Config>(
+	snapshot: &Vec<(T::AccountId, VoteWeight, Vec<T::AccountId>)>,
+) -> Box<dyn Fn(&T::AccountId) -> Option<CompactVoterIndexOf<T>> + '_> {
+	Box::new(move |who| {
+		snapshot
+			.iter()
+			.position(|(x, _, _)| x == who)
+			.and_then(|i| <usize as TryInto<CompactVoterIndexOf<T>>>::try_into(i).ok())
+	})
+}
+
+/// Create a function the returns the index a targets in the snapshot.
+///
+/// The returning index type is the same as the one defined in [`T::CompactSolution::Target`].
+pub fn target_index_fn_linear<T: Config>(
+	snapshot: &Vec<T::AccountId>,
+) -> Box<dyn Fn(&T::AccountId) -> Option<CompactTargetIndexOf<T>> + '_> {
+	Box::new(move |who| {
+		snapshot
+			.iter()
+			.position(|x| x == who)
+			.and_then(|i| <usize as TryInto<CompactTargetIndexOf<T>>>::try_into(i).ok())
+	})
+}
+
+/// Create a function that can map a voter index ([`CompactVoterIndexOf`]) to the actual voter
+/// account using a linearly indexible snapshot.
+pub fn voter_at_fn<T: Config>(
+	snapshot: &Vec<(T::AccountId, VoteWeight, Vec<T::AccountId>)>,
+) -> Box<dyn Fn(CompactVoterIndexOf<T>) -> Option<T::AccountId> + '_> {
+	Box::new(move |i| {
+		<CompactVoterIndexOf<T> as TryInto<usize>>::try_into(i)
+			.ok()
+			.and_then(|i| snapshot.get(i).map(|(x, _, _)| x).cloned())
+	})
+}
+
+/// Create a function that can map a target index ([`CompactTargetIndexOf`]) to the actual target
+/// account using a linearly indexible snapshot.
+pub fn target_at_fn<T: Config>(
+	snapshot: &Vec<T::AccountId>,
+) -> Box<dyn Fn(CompactTargetIndexOf<T>) -> Option<T::AccountId> + '_> {
+	Box::new(move |i| {
+		<CompactTargetIndexOf<T> as TryInto<usize>>::try_into(i)
+			.ok()
+			.and_then(|i| snapshot.get(i).cloned())
+	})
+}
+
+/// Create a function to get the stake of a voter.
+///
+/// This is not optimized and uses a linear search.
+pub fn stake_of_fn_linear<T: Config>(
+	snapshot: &Vec<(T::AccountId, VoteWeight, Vec<T::AccountId>)>,
+) -> Box<dyn Fn(&T::AccountId) -> VoteWeight + '_> {
+	Box::new(move |who| {
+		snapshot.iter().find(|(x, _, _)| x == who).map(|(_, x, _)| *x).unwrap_or_default()
+	})
+}
+
+/// Create a function to get the stake of a voter.
+///
+/// ## Warning
+///
+/// The cache need must be derived from the same snapshot. Zero is returned if a voter is
+/// non-existent.
+pub fn stake_of_fn<'a, T: Config>(
+	snapshot: &'a Vec<(T::AccountId, VoteWeight, Vec<T::AccountId>)>,
+	cache: &'a BTreeMap<T::AccountId, usize>,
+) -> Box<dyn Fn(&T::AccountId) -> VoteWeight + 'a> {
+	Box::new(move |who| {
+		if let Some(index) = cache.get(who) {
+			snapshot.get(*index).map(|(_, x, _)| x).cloned().unwrap_or_default()
+		} else {
+			0
+		}
+	})
+}