update v0.6: high/low balance separation (ethereum/consensus-specs#728)

beacon/src/config.rs

@@ -35,7 +35,7 @@ pub trait Config {
 	/// Maximum deposit amount.
 	fn max_deposit_amount(&self) -> Gwei;
 	/// Fork choice balance increment.
-	fn fork_choice_balance_increment(&self) -> Gwei;
+	fn high_balance_increment(&self) -> Gwei;
 	/// Ejection balance.
 	fn ejection_balance(&self) -> Gwei;
 	/// Genesis fork version.
@@ -241,8 +241,8 @@ pub struct NoVerificationConfig {
 	pub min_deposit_amount: Gwei,
 	/// Maximum deposit amount.
 	pub max_deposit_amount: Gwei,
-	/// Fork choice balance increment.
-	pub fork_choice_balance_increment: Gwei,
+	/// High balance increment.
+	pub high_balance_increment: Gwei,
 	/// Ejection balance.
 	pub ejection_balance: Gwei,
 	/// Genesis fork version.
@@ -327,7 +327,7 @@ impl Config for NoVerificationConfig {
 	fn deposit_contract_tree_depth(&self) -> usize { self.deposit_contract_tree_depth }
 	fn min_deposit_amount(&self) -> Gwei { self.min_deposit_amount }
 	fn max_deposit_amount(&self) -> Gwei { self.max_deposit_amount }
-	fn fork_choice_balance_increment(&self) -> Gwei { self.fork_choice_balance_increment }
+	fn high_balance_increment(&self) -> Gwei { self.high_balance_increment }
 	fn ejection_balance(&self) -> Gwei { self.ejection_balance }
 	fn genesis_fork_version(&self) -> Version { Version::from(self.genesis_fork_version) }
 	fn genesis_slot(&self) -> Slot { self.genesis_slot }
@@ -401,7 +401,7 @@ impl NoVerificationConfig {
 			deposit_contract_tree_depth: 32,
 			min_deposit_amount: 1_000_000_000,
 			max_deposit_amount: 32_000_000_000,
-			fork_choice_balance_increment: 1_000_000_000,
+			high_balance_increment: 1_000_000_000,
 			ejection_balance: 16_000_000_000,
 			genesis_fork_version: [0, 0, 0, 0],
 			genesis_slot: 4294967296,
@@ -452,7 +452,7 @@ impl NoVerificationConfig {
 			deposit_contract_tree_depth: 32,
 			min_deposit_amount: 1_000_000_000,
 			max_deposit_amount: 32_000_000_000,
-			fork_choice_balance_increment: 1_000_000_000,
+			high_balance_increment: 1_000_000_000,
 			ejection_balance: 16_000_000_000,
 			genesis_fork_version: [0, 0, 0, 0],
 			genesis_slot: 4294967296,

beacon/src/executive/mod.rs

@@ -155,8 +155,35 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 		Ok(self.earliest_attestation(index)?.inclusion_slot)
 	}
 
+	fn balance(&self, index: ValidatorIndex) -> Gwei {
+		self.state.balances[index as usize]
+	}
+
+	fn set_balance(&mut self, index: ValidatorIndex, balance: Gwei) {
+		let half_increment = self.config.high_balance_increment() / 2;
+
+		let validator = &mut self.state.validator_registry[index as usize];
+		if validator.high_balance > balance || validator.high_balance + 3 * half_increment < balance {
+			validator.high_balance = balance - balance % self.config.high_balance_increment();
+		}
+		self.state.balances[index as usize] = balance;
+	}
+
+	fn increase_balance(&mut self, index: ValidatorIndex, delta: Gwei) {
+		self.set_balance(index, self.balance(index) + delta);
+	}
+
+	fn decrease_balance(&mut self, index: ValidatorIndex, delta: Gwei) {
+		let cur_balance = self.balance(index);
+		self.set_balance(index, if cur_balance >= delta {
+			cur_balance - delta
+		} else {
+			0
+		});
+	}
+
 	fn effective_balance(&self, index: ValidatorIndex) -> Gwei {
-		core::cmp::min(self.state.validator_balances[index as usize], self.config.max_deposit_amount())
+		core::cmp::min(self.balance(index), self.config.max_deposit_amount())
 	}
 
 	fn total_balance(&self, indices: &[ValidatorIndex]) -> Gwei {
@@ -309,7 +336,7 @@ pub fn genesis_state<C: Config>(deposits: Vec<Deposit>, genesis_time: Timestamp,
 		},
 
 		validator_registry: Vec::new(),
-		validator_balances: Vec::new(),
+		balances: Vec::new(),
 		validator_registry_update_epoch: config.genesis_epoch(),
 
 		latest_randao_mixes: {

beacon/src/executive/per_block.rs

@@ -20,8 +20,8 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 
 		let whistleblower_index = self.beacon_proposer_index(self.state.slot, false)?;
 		let whistleblower_reward = self.effective_balance(index) / self.config.whistleblower_reward_quotient();
-		self.state.validator_balances[whistleblower_index as usize] += whistleblower_reward;
-		self.state.validator_balances[index as usize] -= whistleblower_reward;
+		self.increase_balance(whistleblower_index, whistleblower_reward);
+		self.decrease_balance(index, whistleblower_reward);
 		self.state.validator_registry[index as usize].slashed = true;
 		self.state.validator_registry[index as usize].withdrawable_epoch = self.current_epoch() + self.config.latest_slashed_exit_length() as u64;
 
@@ -324,7 +324,7 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 
 		match self.state.validator_index_by_id(&deposit.deposit_data.deposit_input.pubkey) {
 			Some(index) => {
-				self.state.validator_balances[index as usize] += deposit.deposit_data.amount;
+				self.increase_balance(index, deposit.deposit_data.amount);
 			},
 			None => {
 				if !deposit.is_proof_valid(
@@ -342,10 +342,14 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 					withdrawable_epoch: self.config.far_future_epoch(),
 					initiated_exit: false,
 					slashed: false,
+					high_balance: 0,
 				};
+				let validator_index = self.state.validator_registry.len() as u64;
 
 				self.state.validator_registry.push(validator);
-				self.state.validator_balances.push(deposit.deposit_data.amount);
+				self.state.balances.push(0);
+
+				self.set_balance(validator_index, deposit.deposit_data.amount);
 			},
 		}
 
@@ -389,11 +393,11 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 
 	/// Push a new `Transfer` to the state.
 	pub fn push_transfer(&mut self, transfer: Transfer) -> Result<(), Error> {
-		if self.state.validator_balances[transfer.sender as usize] < core::cmp::max(transfer.amount, transfer.fee) {
+		if self.balance(transfer.sender) < core::cmp::max(transfer.amount, transfer.fee) {
 			return Err(Error::TransferNoFund)
 		}
 
-		if !(self.state.validator_balances[transfer.sender as usize] == transfer.amount + transfer.fee || self.state.validator_balances[transfer.sender as usize] >= transfer.amount + transfer.fee + self.config.min_deposit_amount()) {
+		if !(self.balance(transfer.sender) == transfer.amount + transfer.fee || self.balance(transfer.sender) >= transfer.amount + transfer.fee + self.config.min_deposit_amount()) {
 			return Err(Error::TransferNoFund)
 		}
 
@@ -418,10 +422,10 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 			return Err(Error::TransferInvalidSignature)
 		}
 
-		self.state.validator_balances[transfer.sender as usize] -= transfer.amount + transfer.fee;
-		self.state.validator_balances[transfer.recipient as usize] += transfer.amount;
+		self.decrease_balance(transfer.sender, transfer.amount + transfer.fee);
+		self.increase_balance(transfer.recipient, transfer.amount);
 		let proposer_index = self.beacon_proposer_index(self.state.slot, false)?;
-		self.state.validator_balances[proposer_index as usize] += transfer.fee;
+		self.increase_balance(proposer_index, transfer.fee);
 
 		Ok(())
 	}

beacon/src/executive/per_epoch.rs

@@ -290,7 +290,9 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 		let delta1 = self.justification_and_finalization_deltas()?;
 		let delta2 = self.crosslink_deltas()?;
 		for i in 0..self.state.validator_registry.len() {
-			self.state.validator_balances[i] = (self.state.validator_balances[i] + delta1.0[i] + delta2.0[i]).saturating_sub(delta1.1[i] + delta2.1[i]);
+			let new_balance = (self.balance(i as u64) + delta1.0[i] + delta2.0[i])
+				.saturating_sub(delta1.1[i] + delta2.1[i]);
+			self.set_balance(i as u64, new_balance);
 		}
 
 		Ok(())
@@ -299,7 +301,7 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 	/// Update validator ejections.
 	pub fn update_ejections(&mut self) {
 		for index in self.state.active_validator_indices(self.current_epoch()) {
-			if self.state.validator_balances[index as usize] < self.config.ejection_balance() {
+			if self.balance(index) < self.config.ejection_balance() {
 				self.initiate_validator_exit(index);
 			}
 		}
@@ -333,7 +335,7 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 		let mut balance_churn = 0;
 		for (i, validator) in self.state.validator_registry.clone().into_iter().enumerate() {
 			let index = i as u64;
-			if validator.activation_epoch == self.config.far_future_epoch() && self.state.validator_balances[i] >= self.config.max_deposit_amount() {
+			if validator.activation_epoch == self.config.far_future_epoch() && self.balance(index) >= self.config.max_deposit_amount() {
 				balance_churn += self.effective_balance(index);
 				if balance_churn > max_balance_churn {
 					break
@@ -407,7 +409,7 @@ impl<'state, 'config, C: Config> Executive<'state, 'config, C> {
 					self.effective_balance(index) * core::cmp::min(total_penalties * 3, total_balance) / total_balance,
 					self.effective_balance(index) / self.config.min_penalty_quotient()
 				);
-				self.state.validator_balances[i] -= penalty;
+				self.decrease_balance(index, penalty);
 			}
 		}
 	}

beacon/src/state.rs

@@ -47,8 +47,8 @@ pub struct BeaconState {
 
 	/// Validator registry.
 	pub validator_registry: Vec<Validator>,
-	/// Validator balances.
-	pub validator_balances: Vec<u64>,
+	/// Balances.
+	pub balances: Vec<u64>,
 	/// Last validator registry update epoch.
 	pub validator_registry_update_epoch: Epoch,
 

beacon/src/validator.rs

@@ -44,6 +44,8 @@ pub struct Validator {
 	pub initiated_exit: bool,
 	/// Was the validator slashed
 	pub slashed: bool,
+	/// High balance
+	pub high_balance: u64,
 }
 
 impl Validator {