lighthouse/eth2/state_processing/src/epoch_processable.rs

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use integer_sqrt::IntegerSquareRoot;
use log::{debug, trace};
use rayon::prelude::*;
use ssz::TreeHash;
use std::collections::{HashMap, HashSet};
use std::iter::FromIterator;
use types::{
beacon_state::{AttestationParticipantsError, BeaconStateError, InclusionError},
validator_registry::get_active_validator_indices,
BeaconState, ChainSpec, Crosslink, Epoch, Hash256, PendingAttestation,
};
macro_rules! safe_add_assign {
($a: expr, $b: expr) => {
$a = $a.saturating_add($b);
};
}
macro_rules! safe_sub_assign {
($a: expr, $b: expr) => {
$a = $a.saturating_sub($b);
};
}
#[derive(Debug, PartialEq)]
pub enum Error {
UnableToDetermineProducer,
NoBlockRoots,
BaseRewardQuotientIsZero,
NoRandaoSeed,
BeaconStateError(BeaconStateError),
AttestationParticipantsError(AttestationParticipantsError),
InclusionError(InclusionError),
WinningRootError(WinningRootError),
}
#[derive(Debug, PartialEq)]
pub enum WinningRootError {
NoWinningRoot,
AttestationParticipantsError(AttestationParticipantsError),
}
#[derive(Clone)]
pub struct WinningRoot {
pub shard_block_root: Hash256,
pub attesting_validator_indices: Vec<usize>,
pub total_balance: u64,
pub total_attesting_balance: u64,
}
pub trait EpochProcessable {
fn per_epoch_processing(&mut self, spec: &ChainSpec) -> Result<(), Error>;
}
impl EpochProcessable for BeaconState {
// Cyclomatic complexity is ignored. It would be ideal to split this function apart, however it
// remains monolithic to allow for easier spec updates. Once the spec is more stable we can
// optimise.
#[allow(clippy::cyclomatic_complexity)]
fn per_epoch_processing(&mut self, spec: &ChainSpec) -> Result<(), Error> {
let current_epoch = self.current_epoch(spec);
let previous_epoch = self.previous_epoch(spec);
let next_epoch = self.next_epoch(spec);
debug!(
"Starting per-epoch processing on epoch {}...",
self.current_epoch(spec)
);
/*
* Validators attesting during the current epoch.
*/
let active_validator_indices = get_active_validator_indices(
&self.validator_registry,
self.slot.epoch(spec.epoch_length),
);
let current_total_balance = self.get_total_balance(&active_validator_indices[..], spec);
trace!(
"{} validators with a total balance of {} wei.",
active_validator_indices.len(),
current_total_balance
);
let current_epoch_attestations: Vec<&PendingAttestation> = self
.latest_attestations
.par_iter()
.filter(|a| {
(a.data.slot / spec.epoch_length).epoch(spec.epoch_length)
== self.current_epoch(spec)
})
.collect();
trace!(
"Current epoch attestations: {}",
current_epoch_attestations.len()
);
let current_epoch_boundary_attestations: Vec<&PendingAttestation> =
current_epoch_attestations
.par_iter()
.filter(
|a| match self.get_block_root(self.current_epoch_start_slot(spec), spec) {
Some(block_root) => {
(a.data.epoch_boundary_root == *block_root)
&& (a.data.justified_epoch == self.justified_epoch)
}
None => unreachable!(),
},
)
.cloned()
.collect();
let current_epoch_boundary_attester_indices = self
.get_attestation_participants_union(&current_epoch_boundary_attestations[..], spec)?;
let current_epoch_boundary_attesting_balance =
self.get_total_balance(&current_epoch_boundary_attester_indices[..], spec);
trace!(
"Current epoch boundary attesters: {}",
current_epoch_boundary_attester_indices.len()
);
/*
* Validators attesting during the previous epoch
*/
/*
* Validators that made an attestation during the previous epoch
*/
let previous_epoch_attestations: Vec<&PendingAttestation> = self
.latest_attestations
.par_iter()
.filter(|a| {
//TODO: ensure these saturating subs are correct.
(a.data.slot / spec.epoch_length).epoch(spec.epoch_length)
== self.previous_epoch(spec)
})
.collect();
debug!(
"previous epoch attestations: {}",
previous_epoch_attestations.len()
);
let previous_epoch_attester_indices =
self.get_attestation_participants_union(&previous_epoch_attestations[..], spec)?;
let previous_total_balance = self.get_total_balance(
&get_active_validator_indices(&self.validator_registry, previous_epoch),
spec,
);
/*
* Validators targetting the previous justified slot
*/
let previous_epoch_justified_attestations: Vec<&PendingAttestation> = {
let mut a: Vec<&PendingAttestation> = current_epoch_attestations
.iter()
.filter(|a| a.data.justified_epoch == self.previous_justified_epoch)
.cloned()
.collect();
let mut b: Vec<&PendingAttestation> = previous_epoch_attestations
.iter()
.filter(|a| a.data.justified_epoch == self.previous_justified_epoch)
.cloned()
.collect();
a.append(&mut b);
a
};
let previous_epoch_justified_attester_indices = self
.get_attestation_participants_union(&previous_epoch_justified_attestations[..], spec)?;
let previous_epoch_justified_attesting_balance =
self.get_total_balance(&previous_epoch_justified_attester_indices[..], spec);
/*
* Validators justifying the epoch boundary block at the start of the previous epoch
*/
let previous_epoch_boundary_attestations: Vec<&PendingAttestation> =
previous_epoch_justified_attestations
.iter()
.filter(
|a| match self.get_block_root(self.previous_epoch_start_slot(spec), spec) {
Some(block_root) => a.data.epoch_boundary_root == *block_root,
None => unreachable!(),
},
)
.cloned()
.collect();
let previous_epoch_boundary_attester_indices = self
.get_attestation_participants_union(&previous_epoch_boundary_attestations[..], spec)?;
let previous_epoch_boundary_attesting_balance =
self.get_total_balance(&previous_epoch_boundary_attester_indices[..], spec);
/*
* Validators attesting to the expected beacon chain head during the previous epoch.
*/
let previous_epoch_head_attestations: Vec<&PendingAttestation> =
previous_epoch_attestations
.iter()
.filter(|a| match self.get_block_root(a.data.slot, spec) {
Some(block_root) => a.data.beacon_block_root == *block_root,
None => unreachable!(),
})
.cloned()
.collect();
let previous_epoch_head_attester_indices =
self.get_attestation_participants_union(&previous_epoch_head_attestations[..], spec)?;
let previous_epoch_head_attesting_balance =
self.get_total_balance(&previous_epoch_head_attester_indices[..], spec);
debug!(
"previous_epoch_head_attester_balance of {} wei.",
previous_epoch_head_attesting_balance
);
/*
* Eth1 Data
*/
if self.next_epoch(spec) % spec.eth1_data_voting_period == 0 {
for eth1_data_vote in &self.eth1_data_votes {
if eth1_data_vote.vote_count * 2 > spec.eth1_data_voting_period {
self.latest_eth1_data = eth1_data_vote.eth1_data.clone();
}
}
self.eth1_data_votes = vec![];
}
/*
* Justification
*/
let mut new_justified_epoch = self.justified_epoch;
self.justification_bitfield <<= 1;
// If > 2/3 of the total balance attested to the previous epoch boundary
//
// - Set the 2nd bit of the bitfield.
// - Set the previous epoch to be justified.
if (3 * previous_epoch_boundary_attesting_balance) >= (2 * current_total_balance) {
self.justification_bitfield |= 2;
new_justified_epoch = previous_epoch;
trace!(">= 2/3 voted for previous epoch boundary");
}
// If > 2/3 of the total balance attested to the previous epoch boundary
//
// - Set the 1st bit of the bitfield.
// - Set the current epoch to be justified.
if (3 * current_epoch_boundary_attesting_balance) >= (2 * current_total_balance) {
self.justification_bitfield |= 1;
new_justified_epoch = current_epoch;
trace!(">= 2/3 voted for current epoch boundary");
}
// If:
//
// - All three epochs prior to this epoch have been justified.
// - The previous justified justified epoch was three epochs ago.
//
// Then, set the finalized epoch to be three epochs ago.
if ((self.justification_bitfield >> 1) % 8 == 0b111)
& (self.previous_justified_epoch == previous_epoch - 2)
{
self.finalized_epoch = self.previous_justified_epoch;
trace!("epoch - 3 was finalized (1st condition).");
}
// If:
//
// - Both two epochs prior to this epoch have been justified.
// - The previous justified epoch was two epochs ago.
//
// Then, set the finalized epoch to two epochs ago.
if ((self.justification_bitfield >> 1) % 4 == 0b11)
& (self.previous_justified_epoch == previous_epoch - 1)
{
self.finalized_epoch = self.previous_justified_epoch;
trace!("epoch - 2 was finalized (2nd condition).");
}
// If:
//
// - This epoch and the two prior have been justified.
// - The presently justified epoch was two epochs ago.
//
// Then, set the finalized epoch to two epochs ago.
if (self.justification_bitfield % 8 == 0b111) & (self.justified_epoch == previous_epoch - 1)
{
self.finalized_epoch = self.justified_epoch;
trace!("epoch - 2 was finalized (3rd condition).");
}
// If:
//
// - This epoch and the epoch prior to it have been justified.
// - Set the previous epoch to be justified.
//
// Then, set the finalized epoch to be the previous epoch.
if (self.justification_bitfield % 4 == 0b11) & (self.justified_epoch == previous_epoch) {
self.finalized_epoch = self.justified_epoch;
trace!("epoch - 1 was finalized (4th condition).");
}
self.previous_justified_epoch = self.justified_epoch;
self.justified_epoch = new_justified_epoch;
debug!(
"Finalized epoch {}, justified epoch {}.",
self.finalized_epoch, self.justified_epoch
);
/*
* Crosslinks
*/
// Cached for later lookups.
let mut winning_root_for_shards: HashMap<u64, Result<WinningRoot, WinningRootError>> =
HashMap::new();
// for slot in self.slot.saturating_sub(2 * spec.epoch_length)..self.slot {
for slot in self.previous_epoch(spec).slot_iter(spec.epoch_length) {
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trace!(
"Finding winning root for slot: {} (epoch: {})",
slot,
slot.epoch(spec.epoch_length)
);
let crosslink_committees_at_slot =
self.get_crosslink_committees_at_slot(slot, false, spec)?;
for (crosslink_committee, shard) in crosslink_committees_at_slot {
let shard = shard as u64;
let winning_root = winning_root(
self,
shard,
&current_epoch_attestations,
&previous_epoch_attestations,
spec,
);
if let Ok(winning_root) = &winning_root {
let total_committee_balance =
self.get_total_balance(&crosslink_committee[..], spec);
if (3 * winning_root.total_attesting_balance) >= (2 * total_committee_balance) {
self.latest_crosslinks[shard as usize] = Crosslink {
epoch: current_epoch,
shard_block_root: winning_root.shard_block_root,
}
}
}
winning_root_for_shards.insert(shard, winning_root);
}
}
trace!(
"Found {} winning shard roots.",
winning_root_for_shards.len()
);
/*
* Rewards and Penalities
*/
let base_reward_quotient =
previous_total_balance.integer_sqrt() / spec.base_reward_quotient;
if base_reward_quotient == 0 {
return Err(Error::BaseRewardQuotientIsZero);
}
/*
* Justification and finalization
*/
let epochs_since_finality = next_epoch - self.finalized_epoch;
let previous_epoch_justified_attester_indices_hashset: HashSet<usize> =
HashSet::from_iter(previous_epoch_justified_attester_indices.iter().cloned());
let previous_epoch_boundary_attester_indices_hashset: HashSet<usize> =
HashSet::from_iter(previous_epoch_boundary_attester_indices.iter().cloned());
let previous_epoch_head_attester_indices_hashset: HashSet<usize> =
HashSet::from_iter(previous_epoch_head_attester_indices.iter().cloned());
let previous_epoch_attester_indices_hashset: HashSet<usize> =
HashSet::from_iter(previous_epoch_attester_indices.iter().cloned());
let active_validator_indices_hashset: HashSet<usize> =
HashSet::from_iter(active_validator_indices.iter().cloned());
debug!("previous epoch justified attesters: {}, previous epoch boundary attesters: {}, previous epoch head attesters: {}, previous epoch attesters: {}", previous_epoch_justified_attester_indices.len(), previous_epoch_boundary_attester_indices.len(), previous_epoch_head_attester_indices.len(), previous_epoch_attester_indices.len());
debug!("{} epochs since finality.", epochs_since_finality);
if epochs_since_finality <= 4 {
for index in 0..self.validator_balances.len() {
let base_reward = self.base_reward(index, base_reward_quotient, spec);
if previous_epoch_justified_attester_indices_hashset.contains(&index) {
safe_add_assign!(
self.validator_balances[index],
base_reward * previous_epoch_justified_attesting_balance
/ previous_total_balance
);
} else if active_validator_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], base_reward);
}
if previous_epoch_boundary_attester_indices_hashset.contains(&index) {
safe_add_assign!(
self.validator_balances[index],
base_reward * previous_epoch_boundary_attesting_balance
/ previous_total_balance
);
} else if active_validator_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], base_reward);
}
if previous_epoch_head_attester_indices_hashset.contains(&index) {
safe_add_assign!(
self.validator_balances[index],
base_reward * previous_epoch_head_attesting_balance
/ previous_total_balance
);
} else if active_validator_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], base_reward);
}
}
for index in previous_epoch_attester_indices {
let base_reward = self.base_reward(index, base_reward_quotient, spec);
let inclusion_distance =
self.inclusion_distance(&previous_epoch_attestations, index, spec)?;
safe_add_assign!(
self.validator_balances[index],
base_reward * spec.min_attestation_inclusion_delay / inclusion_distance
)
}
} else {
for index in 0..self.validator_balances.len() {
let inactivity_penalty = self.inactivity_penalty(
index,
epochs_since_finality,
base_reward_quotient,
spec,
);
if active_validator_indices_hashset.contains(&index) {
if !previous_epoch_justified_attester_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], inactivity_penalty);
}
if !previous_epoch_boundary_attester_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], inactivity_penalty);
}
if !previous_epoch_head_attester_indices_hashset.contains(&index) {
safe_sub_assign!(self.validator_balances[index], inactivity_penalty);
}
if self.validator_registry[index].penalized_epoch <= current_epoch {
let base_reward = self.base_reward(index, base_reward_quotient, spec);
safe_sub_assign!(
self.validator_balances[index],
2 * inactivity_penalty + base_reward
);
}
}
}
for index in previous_epoch_attester_indices {
let base_reward = self.base_reward(index, base_reward_quotient, spec);
let inclusion_distance =
self.inclusion_distance(&previous_epoch_attestations, index, spec)?;
safe_sub_assign!(
self.validator_balances[index],
base_reward
- base_reward * spec.min_attestation_inclusion_delay / inclusion_distance
);
}
}
trace!("Processed validator justification and finalization rewards/penalities.");
/*
* Attestation inclusion
*/
for &index in &previous_epoch_attester_indices_hashset {
let inclusion_slot =
self.inclusion_slot(&previous_epoch_attestations[..], index, spec)?;
let proposer_index = self
.get_beacon_proposer_index(inclusion_slot, spec)
.map_err(|_| Error::UnableToDetermineProducer)?;
let base_reward = self.base_reward(proposer_index, base_reward_quotient, spec);
safe_add_assign!(
self.validator_balances[proposer_index],
base_reward / spec.includer_reward_quotient
);
}
trace!(
"Previous epoch attesters: {}.",
previous_epoch_attester_indices_hashset.len()
);
/*
* Crosslinks
*/
for slot in self.previous_epoch(spec).slot_iter(spec.epoch_length) {
let crosslink_committees_at_slot =
self.get_crosslink_committees_at_slot(slot, false, spec)?;
for (_crosslink_committee, shard) in crosslink_committees_at_slot {
let shard = shard as u64;
if let Some(Ok(winning_root)) = winning_root_for_shards.get(&shard) {
// TODO: remove the map.
let attesting_validator_indices: HashSet<usize> = HashSet::from_iter(
winning_root.attesting_validator_indices.iter().cloned(),
);
for index in 0..self.validator_balances.len() {
let base_reward = self.base_reward(index, base_reward_quotient, spec);
if attesting_validator_indices.contains(&index) {
safe_add_assign!(
self.validator_balances[index],
base_reward * winning_root.total_attesting_balance
/ winning_root.total_balance
);
} else {
safe_sub_assign!(self.validator_balances[index], base_reward);
}
}
for index in &winning_root.attesting_validator_indices {
let base_reward = self.base_reward(*index, base_reward_quotient, spec);
safe_add_assign!(
self.validator_balances[*index],
base_reward * winning_root.total_attesting_balance
/ winning_root.total_balance
);
}
}
}
}
/*
* Ejections
*/
self.process_ejections(spec);
/*
* Validator Registry
*/
self.previous_calculation_epoch = self.current_calculation_epoch;
self.previous_epoch_start_shard = self.current_epoch_start_shard;
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debug!(
"setting previous_epoch_seed to : {}",
self.current_epoch_seed
);
self.previous_epoch_seed = self.current_epoch_seed;
let should_update_validator_registy = if self.finalized_epoch
> self.validator_registry_update_epoch
{
(0..self.get_current_epoch_committee_count(spec)).all(|i| {
let shard = (self.current_epoch_start_shard + i as u64) % spec.shard_count;
self.latest_crosslinks[shard as usize].epoch > self.validator_registry_update_epoch
})
} else {
false
};
if should_update_validator_registy {
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trace!("updating validator registry.");
self.update_validator_registry(spec);
self.current_calculation_epoch = next_epoch;
self.current_epoch_start_shard = (self.current_epoch_start_shard
+ self.get_current_epoch_committee_count(spec) as u64)
% spec.shard_count;
self.current_epoch_seed = self.generate_seed(self.current_calculation_epoch, spec)?
} else {
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trace!("not updating validator registry.");
let epochs_since_last_registry_update =
current_epoch - self.validator_registry_update_epoch;
if (epochs_since_last_registry_update > 1)
& epochs_since_last_registry_update.is_power_of_two()
{
self.current_calculation_epoch = next_epoch;
self.current_epoch_seed =
self.generate_seed(self.current_calculation_epoch, spec)?
}
}
self.process_penalties_and_exits(spec);
self.latest_index_roots[(next_epoch.as_usize() + spec.entry_exit_delay as usize)
% spec.latest_index_roots_length] = hash_tree_root(get_active_validator_indices(
&self.validator_registry,
next_epoch + Epoch::from(spec.entry_exit_delay),
));
self.latest_penalized_balances[next_epoch.as_usize() % spec.latest_penalized_exit_length] =
self.latest_penalized_balances
[current_epoch.as_usize() % spec.latest_penalized_exit_length];
self.latest_randao_mixes[next_epoch.as_usize() % spec.latest_randao_mixes_length] = self
.get_randao_mix(current_epoch, spec)
.and_then(|x| Some(*x))
.ok_or_else(|| Error::NoRandaoSeed)?;
self.latest_attestations = self
.latest_attestations
.iter()
.filter(|a| a.data.slot.epoch(spec.epoch_length) >= current_epoch)
.cloned()
.collect();
debug!("Epoch transition complete.");
Ok(())
}
}
fn hash_tree_root<T: TreeHash>(input: Vec<T>) -> Hash256 {
Hash256::from(&input.hash_tree_root()[..])
}
fn winning_root(
state: &BeaconState,
shard: u64,
current_epoch_attestations: &[&PendingAttestation],
previous_epoch_attestations: &[&PendingAttestation],
spec: &ChainSpec,
) -> Result<WinningRoot, WinningRootError> {
let mut attestations = current_epoch_attestations.to_vec();
attestations.append(&mut previous_epoch_attestations.to_vec());
let mut candidates: HashMap<Hash256, WinningRoot> = HashMap::new();
let mut highest_seen_balance = 0;
for a in &attestations {
if a.data.shard != shard {
continue;
}
let shard_block_root = &a.data.shard_block_root;
if candidates.contains_key(shard_block_root) {
continue;
}
// TODO: `cargo fmt` makes this rather ugly; tidy up.
let attesting_validator_indices = attestations.iter().try_fold::<_, _, Result<
_,
AttestationParticipantsError,
>>(vec![], |mut acc, a| {
if (a.data.shard == shard) && (a.data.shard_block_root == *shard_block_root) {
acc.append(&mut state.get_attestation_participants(
&a.data,
&a.aggregation_bitfield,
spec,
)?);
}
Ok(acc)
})?;
let total_balance: u64 = attesting_validator_indices
.iter()
.fold(0, |acc, i| acc + state.get_effective_balance(*i, spec));
let total_attesting_balance: u64 = attesting_validator_indices
.iter()
.fold(0, |acc, i| acc + state.get_effective_balance(*i, spec));
if total_attesting_balance > highest_seen_balance {
highest_seen_balance = total_attesting_balance;
}
let candidate_root = WinningRoot {
shard_block_root: *shard_block_root,
attesting_validator_indices,
total_attesting_balance,
total_balance,
};
candidates.insert(*shard_block_root, candidate_root);
}
Ok(candidates
.iter()
.filter_map(|(_hash, candidate)| {
if candidate.total_attesting_balance == highest_seen_balance {
Some(candidate)
} else {
None
}
})
.min_by_key(|candidate| candidate.shard_block_root)
.ok_or_else(|| WinningRootError::NoWinningRoot)?
// TODO: avoid clone.
.clone())
}
impl From<InclusionError> for Error {
fn from(e: InclusionError) -> Error {
Error::InclusionError(e)
}
}
impl From<BeaconStateError> for Error {
fn from(e: BeaconStateError) -> Error {
Error::BeaconStateError(e)
}
}
impl From<AttestationParticipantsError> for Error {
fn from(e: AttestationParticipantsError) -> Error {
Error::AttestationParticipantsError(e)
}
}
impl From<AttestationParticipantsError> for WinningRootError {
fn from(e: AttestationParticipantsError) -> WinningRootError {
WinningRootError::AttestationParticipantsError(e)
}
}
#[cfg(test)]
mod tests {
#[test]
fn it_works() {
assert_eq!(2 + 2, 4);
}
}