Decouple Stkaing and Election - Part1: Support traits (#7908)

* Base features and traits.

* Fix the build

* Remove unused boxing

* Self review cleanup

* Fix build

Cargo.toml

@@ -139,6 +139,7 @@ members = [
 	"primitives/database",
 	"primitives/debug-derive",
 	"primitives/externalities",
+	"primitives/election-providers",
 	"primitives/finality-grandpa",
 	"primitives/inherents",
 	"primitives/io",

frame/staking/src/benchmarking.rs

@@ -21,6 +21,7 @@ use super::*;
 use crate::Module as Staking;
 use testing_utils::*;
 
+use sp_npos_elections::CompactSolution;
 use sp_runtime::traits::One;
 use frame_system::RawOrigin;
 pub use frame_benchmarking::{benchmarks, account, whitelisted_caller, whitelist_account};

frame/staking/src/lib.rs

@@ -232,10 +232,11 @@
 //!
 //! The controller account can free a portion (or all) of the funds using the
 //! [`unbond`](enum.Call.html#variant.unbond) call. Note that the funds are not immediately
-//! accessible. Instead, a duration denoted by [`BondingDuration`](./trait.Config.html#associatedtype.BondingDuration)
-//! (in number of eras) must pass until the funds can actually be removed. Once the
-//! `BondingDuration` is over, the [`withdraw_unbonded`](./enum.Call.html#variant.withdraw_unbonded)
-//! call can be used to actually withdraw the funds.
+//! accessible. Instead, a duration denoted by
+//! [`BondingDuration`](./trait.Config.html#associatedtype.BondingDuration) (in number of eras) must
+//! pass until the funds can actually be removed. Once the `BondingDuration` is over, the
+//! [`withdraw_unbonded`](./enum.Call.html#variant.withdraw_unbonded) call can be used to actually
+//! withdraw the funds.
 //!
 //! Note that there is a limitation to the number of fund-chunks that can be scheduled to be
 //! unlocked in the future via [`unbond`](enum.Call.html#variant.unbond). In case this maximum
@@ -304,7 +305,7 @@ use frame_support::{
 };
 use pallet_session::historical;
 use sp_runtime::{
-	Percent, Perbill, PerU16, PerThing, InnerOf, RuntimeDebug, DispatchError,
+	Percent, Perbill, PerU16, InnerOf, RuntimeDebug, DispatchError,
 	curve::PiecewiseLinear,
 	traits::{
 		Convert, Zero, StaticLookup, CheckedSub, Saturating, SaturatedConversion,
@@ -327,14 +328,14 @@ use frame_system::{
 };
 use sp_npos_elections::{
 	ExtendedBalance, Assignment, ElectionScore, ElectionResult as PrimitiveElectionResult,
-	build_support_map, evaluate_support, seq_phragmen, generate_solution_type,
-	is_score_better, VotingLimit, SupportMap, VoteWeight,
+	to_support_map, EvaluateSupport, seq_phragmen, generate_solution_type, is_score_better,
+	SupportMap, VoteWeight, CompactSolution, PerThing128,
 };
 pub use weights::WeightInfo;
 
 const STAKING_ID: LockIdentifier = *b"staking ";
 pub const MAX_UNLOCKING_CHUNKS: usize = 32;
-pub const MAX_NOMINATIONS: usize = <CompactAssignments as VotingLimit>::LIMIT;
+pub const MAX_NOMINATIONS: usize = <CompactAssignments as CompactSolution>::LIMIT;
 
 pub(crate) const LOG_TARGET: &'static str = "staking";
 
@@ -2105,7 +2106,7 @@ decl_module! {
 		#[weight = T::WeightInfo::submit_solution_better(
 			size.validators.into(),
 			size.nominators.into(),
-			compact.len() as u32,
+			compact.voter_count() as u32,
 			winners.len() as u32,
 		)]
 		pub fn submit_election_solution(
@@ -2139,7 +2140,7 @@ decl_module! {
 		#[weight = T::WeightInfo::submit_solution_better(
 			size.validators.into(),
 			size.nominators.into(),
-			compact.len() as u32,
+			compact.voter_count() as u32,
 			winners.len() as u32,
 		)]
 		pub fn submit_election_solution_unsigned(
@@ -2601,13 +2602,11 @@ impl<T: Config> Module<T> {
 		);
 
 		// build the support map thereof in order to evaluate.
-		let supports = build_support_map::<T::AccountId>(
-			&winners,
-			&staked_assignments,
-		).map_err(|_| Error::<T>::OffchainElectionBogusEdge)?;
+		let supports = to_support_map::<T::AccountId>(&winners, &staked_assignments)
+			.map_err(|_| Error::<T>::OffchainElectionBogusEdge)?;
 
 		// Check if the score is the same as the claimed one.
-		let submitted_score = evaluate_support(&supports);
+		let submitted_score = (&supports).evaluate();
 		ensure!(submitted_score == claimed_score, Error::<T>::OffchainElectionBogusScore);
 
 		// At last, alles Ok. Exposures and store the result.
@@ -2863,7 +2862,7 @@ impl<T: Config> Module<T> {
 				Self::slashable_balance_of_fn(),
 			);
 
-			let supports = build_support_map::<T::AccountId>(
+			let supports = to_support_map::<T::AccountId>(
 				&elected_stashes,
 				&staked_assignments,
 			)
@@ -2902,7 +2901,7 @@ impl<T: Config> Module<T> {
 	/// Self votes are added and nominations before the most recent slashing span are ignored.
 	///
 	/// No storage item is updated.
-	pub fn do_phragmen<Accuracy: PerThing>(
+	pub fn do_phragmen<Accuracy: PerThing128>(
 		iterations: usize,
 	) -> Option<PrimitiveElectionResult<T::AccountId, Accuracy>>
 	where
@@ -2952,7 +2951,7 @@ impl<T: Config> Module<T> {
 				all_nominators,
 				Some((iterations, 0)), // exactly run `iterations` rounds.
 			)
-			.map_err(|err| log!(error, "Call to seq-phragmen failed due to {}", err))
+			.map_err(|err| log!(error, "Call to seq-phragmen failed due to {:?}", err))
 			.ok()
 		}
 	}

frame/staking/src/mock.rs

@@ -27,7 +27,7 @@ use frame_support::{
 use sp_core::H256;
 use sp_io;
 use sp_npos_elections::{
-	build_support_map, evaluate_support, reduce, ExtendedBalance, StakedAssignment, ElectionScore,
+	to_support_map, EvaluateSupport, reduce, ExtendedBalance, StakedAssignment, ElectionScore,
 };
 use sp_runtime::{
 	curve::PiecewiseLinear,
@@ -860,8 +860,8 @@ pub(crate) fn horrible_npos_solution(
 	let score = {
 		let (_, _, better_score) = prepare_submission_with(true, true, 0, |_| {});
 
-		let support = build_support_map::<AccountId>(&winners, &staked_assignment).unwrap();
-		let score = evaluate_support(&support);
+		let support = to_support_map::<AccountId>(&winners, &staked_assignment).unwrap();
+		let score = support.evaluate();
 
 		assert!(sp_npos_elections::is_score_better::<Perbill>(
 			better_score,
@@ -960,11 +960,11 @@ pub(crate) fn prepare_submission_with(
 			Staking::slashable_balance_of_fn(),
 		);
 
-		let support_map = build_support_map::<AccountId>(
+		let support_map = to_support_map::<AccountId>(
 			winners.as_slice(),
 			staked.as_slice(),
 		).unwrap();
-		evaluate_support::<AccountId>(&support_map)
+		support_map.evaluate()
 	} else {
 		Default::default()
 	};

frame/staking/src/offchain_election.rs

@@ -25,8 +25,8 @@ use codec::Decode;
 use frame_support::{traits::Get, weights::Weight, IterableStorageMap};
 use frame_system::offchain::SubmitTransaction;
 use sp_npos_elections::{
-	build_support_map, evaluate_support, reduce, Assignment, ElectionResult, ElectionScore,
-	ExtendedBalance,
+	to_support_map, EvaluateSupport, reduce, Assignment, ElectionResult, ElectionScore,
+	ExtendedBalance, CompactSolution,
 };
 use sp_runtime::{
 	offchain::storage::StorageValueRef, traits::TrailingZeroInput, PerThing, RuntimeDebug,
@@ -265,7 +265,7 @@ pub fn trim_to_weight<T: Config, FN>(
 where
 	for<'r> FN: Fn(&'r T::AccountId) -> Option<NominatorIndex>,
 {
-	match compact.len().checked_sub(maximum_allowed_voters as usize) {
+	match compact.voter_count().checked_sub(maximum_allowed_voters as usize) {
 		Some(to_remove) if to_remove > 0 => {
 			// grab all voters and sort them by least stake.
 			let balance_of = <Module<T>>::slashable_balance_of_fn();
@@ -300,7 +300,7 @@ where
 					warn,
 					"💸 {} nominators out of {} had to be removed from compact solution due to size limits.",
 					removed,
-					compact.len() + removed,
+					compact.voter_count() + removed,
 				);
 			Ok(compact)
 		}
@@ -324,12 +324,7 @@ pub fn prepare_submission<T: Config>(
 	do_reduce: bool,
 	maximum_weight: Weight,
 ) -> Result<
-	(
-		Vec<ValidatorIndex>,
-		CompactAssignments,
-		ElectionScore,
-		ElectionSize,
-	),
+	(Vec<ValidatorIndex>, CompactAssignments, ElectionScore, ElectionSize),
 	OffchainElectionError,
 >
 where
@@ -403,11 +398,11 @@ where
 		T::WeightInfo::submit_solution_better(
 				size.validators.into(),
 				size.nominators.into(),
-				compact.len() as u32,
+				compact.voter_count() as u32,
 				winners.len() as u32,
 		),
 		maximum_allowed_voters,
-		compact.len(),
+		compact.voter_count(),
 	);
 
 	let compact = trim_to_weight::<T, _>(maximum_allowed_voters, compact, &nominator_index)?;
@@ -423,9 +418,9 @@ where
 			<Module<T>>::slashable_balance_of_fn(),
 		);
 
-		let support_map = build_support_map::<T::AccountId>(&winners, &staked)
+		let support_map = to_support_map::<T::AccountId>(&winners, &staked)
 			.map_err(|_| OffchainElectionError::ElectionFailed)?;
-		evaluate_support::<T::AccountId>(&support_map)
+		support_map.evaluate()
 	};
 
 	// winners to index. Use a simple for loop for a more expressive early exit in case of error.

frame/staking/src/testing_utils.rs

@@ -244,11 +244,9 @@ pub fn get_weak_solution<T: Config>(
 			<Module<T>>::slashable_balance_of_fn(),
 		);
 
-		let support_map = build_support_map::<T::AccountId>(
-			winners.as_slice(),
-			staked.as_slice(),
-		).unwrap();
-		evaluate_support::<T::AccountId>(&support_map)
+		let support_map =
+			to_support_map::<T::AccountId>(winners.as_slice(), staked.as_slice()).unwrap();
+		support_map.evaluate()
 	};
 
 	// compact encode the assignment.

primitives/election-providers/Cargo.toml

@@ -0,0 +1,33 @@
+[package]
+name = "sp-election-providers"
+version = "2.0.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+license = "Apache-2.0"
+homepage = "https://substrate.dev"
+repository = "https://github.com/paritytech/substrate/"
+description = "Primitive election providers"
+readme = "README.md"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "1.3.4", default-features = false, features = ["derive"] }
+sp-std = { version = "2.0.1", default-features = false, path = "../std" }
+sp-arithmetic = { version = "2.0.1", default-features = false, path = "../arithmetic" }
+sp-npos-elections = { version = "2.0.1", default-features = false, path = "../npos-elections" }
+
+[dev-dependencies]
+sp-npos-elections = { version = "2.0.1", path = "../npos-elections" }
+sp-runtime = { version = "2.0.1", path = "../runtime" }
+
+[features]
+default = ["std"]
+runtime-benchmarks = []
+std = [
+	"codec/std",
+	"sp-std/std",
+	"sp-npos-elections/std",
+	"sp-arithmetic/std",
+]