[NPoS] Remove better solution threshold for unsigned submissions

polkadot/runtime/westend/src/lib.rs

@@ -531,7 +531,6 @@ parameter_types! {
 	pub const SignedDepositByte: Balance = deposit(0, 10) / 1024;
 	// Each good submission will get 1 WND as reward
 	pub SignedRewardBase: Balance = 1 * UNITS;
-	pub BetterUnsignedThreshold: Perbill = Perbill::from_rational(5u32, 10_000);
 
 	// 1 hour session, 15 minutes unsigned phase, 4 offchain executions.
 	pub OffchainRepeat: BlockNumber = UnsignedPhase::get() / 4;
@@ -608,7 +607,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type MinerConfig = Self;
 	type SlashHandler = (); // burn slashes
 	type RewardHandler = (); // nothing to do upon rewards
-	type BetterUnsignedThreshold = BetterUnsignedThreshold;
 	type BetterSignedThreshold = ();
 	type OffchainRepeat = OffchainRepeat;
 	type MinerTxPriority = NposSolutionPriority;

prdoc/pr_2694.prdoc

@@ -0,0 +1,14 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: "pallet-election-provider-multi-phase: Removes BetterUnsignedThreshold from pallet config"
+
+doc:
+  - audience: Runtime Dev
+    description: |
+      Removes thresholding for accepting solutions better than the last queued for unsigned phase. This is unnecessary
+      as even without thresholding, the number of solutions that can be submitted to on-chain which is better than the
+      previous one is limited.
+
+crates:
+  - name: "pallet-election-provider-multi-phase"

substrate/bin/node/runtime/src/lib.rs

@@ -704,8 +704,6 @@ parameter_types! {
 	pub const SignedDepositIncreaseFactor: Percent = Percent::from_percent(10);
 	pub const SignedDepositByte: Balance = 1 * CENTS;
 
-	pub BetterUnsignedThreshold: Perbill = Perbill::from_rational(1u32, 10_000);
-
 	// miner configs
 	pub const MultiPhaseUnsignedPriority: TransactionPriority = StakingUnsignedPriority::get() - 1u64;
 	pub MinerMaxWeight: Weight = RuntimeBlockWeights::get()
@@ -822,7 +820,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type EstimateCallFee = TransactionPayment;
 	type SignedPhase = SignedPhase;
 	type UnsignedPhase = UnsignedPhase;
-	type BetterUnsignedThreshold = BetterUnsignedThreshold;
 	type BetterSignedThreshold = ();
 	type OffchainRepeat = OffchainRepeat;
 	type MinerTxPriority = MultiPhaseUnsignedPriority;

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

@@ -101,9 +101,8 @@
 //! unsigned transaction, thus the name _unsigned_ phase. This unsigned transaction can never be
 //! valid if propagated, and it acts similar to an inherent.
 //!
-//! Validators will only submit solutions if the one that they have computed is sufficiently better
-//! than the best queued one (see [`pallet::Config::BetterUnsignedThreshold`]) and will limit the
-//! weight of the solution to [`MinerConfig::MaxWeight`].
+//! Validators will only submit solutions if the one that they have computed is strictly better than
+//! the best queued one and will limit the weight of the solution to [`MinerConfig::MaxWeight`].
 //!
 //! The unsigned phase can be made passive depending on how the previous signed phase went, by
 //! setting the first inner value of [`Phase`] to `false`. For now, the signed phase is always
@@ -598,11 +597,6 @@ pub mod pallet {
 		#[pallet::constant]
 		type BetterSignedThreshold: Get<Perbill>;
 
-		/// The minimum amount of improvement to the solution score that defines a solution as
-		/// "better" in the Unsigned phase.
-		#[pallet::constant]
-		type BetterUnsignedThreshold: Get<Perbill>;
-
 		/// The repeat threshold of the offchain worker.
 		///
 		/// For example, if it is 5, that means that at least 5 blocks will elapse between attempts

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

@@ -301,7 +301,6 @@ parameter_types! {
 	pub static SignedMaxWeight: Weight = BlockWeights::get().max_block;
 	pub static MinerTxPriority: u64 = 100;
 	pub static BetterSignedThreshold: Perbill = Perbill::zero();
-	pub static BetterUnsignedThreshold: Perbill = Perbill::zero();
 	pub static OffchainRepeat: BlockNumber = 5;
 	pub static MinerMaxWeight: Weight = BlockWeights::get().max_block;
 	pub static MinerMaxLength: u32 = 256;
@@ -399,7 +398,6 @@ impl crate::Config for Runtime {
 	type EstimateCallFee = frame_support::traits::ConstU32<8>;
 	type SignedPhase = SignedPhase;
 	type UnsignedPhase = UnsignedPhase;
-	type BetterUnsignedThreshold = BetterUnsignedThreshold;
 	type BetterSignedThreshold = BetterSignedThreshold;
 	type OffchainRepeat = OffchainRepeat;
 	type MinerTxPriority = MinerTxPriority;
@@ -538,10 +536,7 @@ impl ExtBuilder {
 		<BetterSignedThreshold>::set(p);
 		self
 	}
-	pub fn better_unsigned_threshold(self, p: Perbill) -> Self {
-		<BetterUnsignedThreshold>::set(p);
-		self
-	}
+
 	pub fn phases(self, signed: BlockNumber, unsigned: BlockNumber) -> Self {
 		<SignedPhase>::set(signed);
 		<UnsignedPhase>::set(unsigned);

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

@@ -386,7 +386,7 @@ impl<T: Config> Pallet<T> {
 		ensure!(
 			Self::queued_solution().map_or(true, |q: ReadySolution<_, _>| raw_solution
 				.score
-				.strict_threshold_better(q.score, T::BetterUnsignedThreshold::get())),
+				.strict_threshold_better(q.score, sp_runtime::Perbill::zero())),
 			Error::<T>::PreDispatchWeakSubmission,
 		);
 
@@ -1025,7 +1025,7 @@ mod tests {
 		bounded_vec,
 		offchain::storage_lock::{BlockAndTime, StorageLock},
 		traits::{Dispatchable, ValidateUnsigned, Zero},
-		ModuleError, PerU16, Perbill,
+		ModuleError, PerU16,
 	};
 
 	type Assignment = crate::unsigned::Assignment<Runtime>;
@@ -1360,20 +1360,22 @@ mod tests {
 			.desired_targets(1)
 			.add_voter(7, 2, bounded_vec![10])
 			.add_voter(8, 5, bounded_vec![10])
-			.better_unsigned_threshold(Perbill::from_percent(50))
 			.build_and_execute(|| {
 				roll_to_unsigned();
 				assert!(MultiPhase::current_phase().is_unsigned());
 				assert_eq!(MultiPhase::desired_targets().unwrap(), 1);
 
 				// an initial solution
 				let result = ElectionResult {
-					// note: This second element of backing stake is not important here.
-					winners: vec![(10, 10)],
-					assignments: vec![Assignment {
-						who: 10,
-						distribution: vec![(10, PerU16::one())],
-					}],
+					winners: vec![(10, 12)],
+					assignments: vec![
+						Assignment { who: 10, distribution: vec![(10, PerU16::one())] },
+						Assignment {
+							who: 7,
+							// note: this percent doesn't even matter, in solution it is 100%.
+							distribution: vec![(10, PerU16::one())],
+						},
+					],
 				};
 
 				let RoundSnapshot { voters, targets } = MultiPhase::snapshot().unwrap();
@@ -1394,19 +1396,16 @@ mod tests {
 					Box::new(solution),
 					witness
 				));
-				assert_eq!(MultiPhase::queued_solution().unwrap().score.minimal_stake, 10);
+				assert_eq!(MultiPhase::queued_solution().unwrap().score.minimal_stake, 12);
 
-				// trial 1: a solution who's score is only 2, i.e. 20% better in the first element.
+				// trial 1: a solution who's minimal stake is 10, i.e. 16% worse than the first
+				// solution.
 				let result = ElectionResult {
-					winners: vec![(10, 12)],
-					assignments: vec![
-						Assignment { who: 10, distribution: vec![(10, PerU16::one())] },
-						Assignment {
-							who: 7,
-							// note: this percent doesn't even matter, in solution it is 100%.
-							distribution: vec![(10, PerU16::one())],
-						},
-					],
+					winners: vec![(10, 10)],
+					assignments: vec![Assignment {
+						who: 10,
+						distribution: vec![(10, PerU16::one())],
+					}],
 				};
 				let (raw, score, _, _) = Miner::<Runtime>::prepare_election_result_with_snapshot(
 					result,
@@ -1416,15 +1415,16 @@ mod tests {
 				)
 				.unwrap();
 				let solution = RawSolution { solution: raw, score, round: MultiPhase::round() };
-				// 12 is not 50% more than 10
-				assert_eq!(solution.score.minimal_stake, 12);
+				// 10 is not better than 12
+				assert_eq!(solution.score.minimal_stake, 10);
 				assert_noop!(
 					MultiPhase::unsigned_pre_dispatch_checks(&solution),
 					Error::<Runtime>::PreDispatchWeakSubmission,
 				);
 				// submitting this will actually panic.
 
-				// trial 2: a solution who's score is only 7, i.e. 70% better in the first element.
+				// trial 2: a solution who's minimal stake is 17, i.e. 5 better than the first
+				// solution.
 				let result = ElectionResult {
 					winners: vec![(10, 12)],
 					assignments: vec![

substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs

@@ -190,7 +190,6 @@ impl pallet_election_provider_multi_phase::Config for Runtime {
 	type SignedPhase = SignedPhase;
 	type UnsignedPhase = UnsignedPhase;
 	type BetterSignedThreshold = ();
-	type BetterUnsignedThreshold = ();
 	type OffchainRepeat = OffchainRepeat;
 	type MinerTxPriority = TransactionPriority;
 	type MinerConfig = Self;