Files
lighthouse/eth2/state_processing/src/per_epoch_processing/apply_rewards.rs
2019-05-08 15:36:02 +10:00

335 lines
11 KiB
Rust

use super::validator_statuses::{TotalBalances, ValidatorStatus, ValidatorStatuses};
use super::{Error, WinningRootHashSet};
use integer_sqrt::IntegerSquareRoot;
use types::*;
/// Use to track the changes to a validators balance.
#[derive(Default, Clone)]
pub struct Delta {
rewards: u64,
penalties: u64,
}
impl Delta {
/// Reward the validator with the `reward`.
pub fn reward(&mut self, reward: u64) {
self.rewards += reward;
}
/// Penalize the validator with the `penalty`.
pub fn penalize(&mut self, penalty: u64) {
self.penalties += penalty;
}
}
impl std::ops::AddAssign for Delta {
/// Use wrapping addition as that is how it's defined in the spec.
fn add_assign(&mut self, other: Delta) {
self.rewards += other.rewards;
self.penalties += other.penalties;
}
}
/// Apply attester and proposer rewards.
///
/// Spec v0.5.1
pub fn apply_rewards<T: BeaconStateTypes>(
state: &mut BeaconState<T>,
validator_statuses: &mut ValidatorStatuses,
winning_root_for_shards: &WinningRootHashSet,
spec: &ChainSpec,
) -> Result<(), Error> {
// Guard against an out-of-bounds during the validator balance update.
if validator_statuses.statuses.len() != state.validator_balances.len() {
return Err(Error::ValidatorStatusesInconsistent);
}
// Guard against an out-of-bounds during the attester inclusion balance update.
if validator_statuses.statuses.len() != state.validator_registry.len() {
return Err(Error::ValidatorStatusesInconsistent);
}
let mut deltas = vec![Delta::default(); state.validator_balances.len()];
get_justification_and_finalization_deltas(&mut deltas, state, &validator_statuses, spec)?;
get_crosslink_deltas(&mut deltas, state, &validator_statuses, spec)?;
// Apply the proposer deltas if we are finalizing normally.
//
// This is executed slightly differently to the spec because of the way our functions are
// structured. It should be functionally equivalent.
if epochs_since_finality(state, spec) <= 4 {
get_proposer_deltas(
&mut deltas,
state,
validator_statuses,
winning_root_for_shards,
spec,
)?;
}
// Apply the deltas, over-flowing but not under-flowing (saturating at 0 instead).
for (i, delta) in deltas.iter().enumerate() {
state.validator_balances[i] += delta.rewards;
state.validator_balances[i] = state.validator_balances[i].saturating_sub(delta.penalties);
}
Ok(())
}
/// Applies the attestation inclusion reward to each proposer for every validator who included an
/// attestation in the previous epoch.
///
/// Spec v0.5.1
fn get_proposer_deltas<T: BeaconStateTypes>(
deltas: &mut Vec<Delta>,
state: &mut BeaconState<T>,
validator_statuses: &mut ValidatorStatuses,
winning_root_for_shards: &WinningRootHashSet,
spec: &ChainSpec,
) -> Result<(), Error> {
// Update statuses with the information from winning roots.
validator_statuses.process_winning_roots(state, winning_root_for_shards, spec)?;
for (index, validator) in validator_statuses.statuses.iter().enumerate() {
let mut delta = Delta::default();
if validator.is_previous_epoch_attester {
let inclusion = validator
.inclusion_info
.expect("It is a logic error for an attester not to have an inclusion distance.");
let base_reward = get_base_reward(
state,
inclusion.proposer_index,
validator_statuses.total_balances.previous_epoch,
spec,
)?;
if inclusion.proposer_index >= deltas.len() {
return Err(Error::ValidatorStatusesInconsistent);
}
delta.reward(base_reward / spec.attestation_inclusion_reward_quotient);
}
deltas[index] += delta;
}
Ok(())
}
/// Apply rewards for participation in attestations during the previous epoch.
///
/// Spec v0.5.1
fn get_justification_and_finalization_deltas<T: BeaconStateTypes>(
deltas: &mut Vec<Delta>,
state: &BeaconState<T>,
validator_statuses: &ValidatorStatuses,
spec: &ChainSpec,
) -> Result<(), Error> {
let epochs_since_finality = epochs_since_finality(state, spec);
for (index, validator) in validator_statuses.statuses.iter().enumerate() {
let base_reward = get_base_reward(
state,
index,
validator_statuses.total_balances.previous_epoch,
spec,
)?;
let inactivity_penalty = get_inactivity_penalty(
state,
index,
epochs_since_finality.as_u64(),
validator_statuses.total_balances.previous_epoch,
spec,
)?;
let delta = if epochs_since_finality <= 4 {
compute_normal_justification_and_finalization_delta(
&validator,
&validator_statuses.total_balances,
base_reward,
spec,
)
} else {
compute_inactivity_leak_delta(&validator, base_reward, inactivity_penalty, spec)
};
deltas[index] += delta;
}
Ok(())
}
/// Determine the delta for a single validator, if the chain is finalizing normally.
///
/// Spec v0.5.1
fn compute_normal_justification_and_finalization_delta(
validator: &ValidatorStatus,
total_balances: &TotalBalances,
base_reward: u64,
spec: &ChainSpec,
) -> Delta {
let mut delta = Delta::default();
let boundary_attesting_balance = total_balances.previous_epoch_boundary_attesters;
let total_balance = total_balances.previous_epoch;
let total_attesting_balance = total_balances.previous_epoch_attesters;
let matching_head_balance = total_balances.previous_epoch_boundary_attesters;
// Expected FFG source.
if validator.is_previous_epoch_attester {
delta.reward(base_reward * total_attesting_balance / total_balance);
// Inclusion speed bonus
let inclusion = validator
.inclusion_info
.expect("It is a logic error for an attester not to have an inclusion distance.");
delta.reward(
base_reward * spec.min_attestation_inclusion_delay / inclusion.distance.as_u64(),
);
} else if validator.is_active_in_previous_epoch {
delta.penalize(base_reward);
}
// Expected FFG target.
if validator.is_previous_epoch_boundary_attester {
delta.reward(base_reward / boundary_attesting_balance / total_balance);
} else if validator.is_active_in_previous_epoch {
delta.penalize(base_reward);
}
// Expected head.
if validator.is_previous_epoch_head_attester {
delta.reward(base_reward * matching_head_balance / total_balance);
} else if validator.is_active_in_previous_epoch {
delta.penalize(base_reward);
};
// Proposer bonus is handled in `apply_proposer_deltas`.
//
// This function only computes the delta for a single validator, so it cannot also return a
// delta for a validator.
delta
}
/// Determine the delta for a single delta, assuming the chain is _not_ finalizing normally.
///
/// Spec v0.5.1
fn compute_inactivity_leak_delta(
validator: &ValidatorStatus,
base_reward: u64,
inactivity_penalty: u64,
spec: &ChainSpec,
) -> Delta {
let mut delta = Delta::default();
if validator.is_active_in_previous_epoch {
if !validator.is_previous_epoch_attester {
delta.penalize(inactivity_penalty);
} else {
// If a validator did attest, apply a small penalty for getting attestations included
// late.
let inclusion = validator
.inclusion_info
.expect("It is a logic error for an attester not to have an inclusion distance.");
delta.reward(
base_reward * spec.min_attestation_inclusion_delay / inclusion.distance.as_u64(),
);
delta.penalize(base_reward);
}
if !validator.is_previous_epoch_boundary_attester {
delta.reward(inactivity_penalty);
}
if !validator.is_previous_epoch_head_attester {
delta.penalize(inactivity_penalty);
}
}
// Penalize slashed-but-inactive validators as though they were active but offline.
if !validator.is_active_in_previous_epoch
& validator.is_slashed
& !validator.is_withdrawable_in_current_epoch
{
delta.penalize(2 * inactivity_penalty + base_reward);
}
delta
}
/// Calculate the deltas based upon the winning roots for attestations during the previous epoch.
///
/// Spec v0.5.1
fn get_crosslink_deltas<T: BeaconStateTypes>(
deltas: &mut Vec<Delta>,
state: &BeaconState<T>,
validator_statuses: &ValidatorStatuses,
spec: &ChainSpec,
) -> Result<(), Error> {
for (index, validator) in validator_statuses.statuses.iter().enumerate() {
let mut delta = Delta::default();
let base_reward = get_base_reward(
state,
index,
validator_statuses.total_balances.previous_epoch,
spec,
)?;
if let Some(ref winning_root) = validator.winning_root_info {
delta.reward(
base_reward * winning_root.total_attesting_balance
/ winning_root.total_committee_balance,
);
} else {
delta.penalize(base_reward);
}
deltas[index] += delta;
}
Ok(())
}
/// Returns the base reward for some validator.
///
/// Spec v0.5.1
fn get_base_reward<T: BeaconStateTypes>(
state: &BeaconState<T>,
index: usize,
previous_total_balance: u64,
spec: &ChainSpec,
) -> Result<u64, BeaconStateError> {
if previous_total_balance == 0 {
Ok(0)
} else {
let adjusted_quotient = previous_total_balance.integer_sqrt() / spec.base_reward_quotient;
Ok(state.get_effective_balance(index, spec)? / adjusted_quotient / 5)
}
}
/// Returns the inactivity penalty for some validator.
///
/// Spec v0.5.1
fn get_inactivity_penalty<T: BeaconStateTypes>(
state: &BeaconState<T>,
index: usize,
epochs_since_finality: u64,
previous_total_balance: u64,
spec: &ChainSpec,
) -> Result<u64, BeaconStateError> {
Ok(get_base_reward(state, index, previous_total_balance, spec)?
+ state.get_effective_balance(index, spec)? * epochs_since_finality
/ spec.inactivity_penalty_quotient
/ 2)
}
/// Returns the epochs since the last finalized epoch.
///
/// Spec v0.5.1
fn epochs_since_finality<T: BeaconStateTypes>(state: &BeaconState<T>, spec: &ChainSpec) -> Epoch {
state.current_epoch(spec) + 1 - state.finalized_epoch
}