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op_pool: use max cover algorithm, refactor

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This commit is contained in:
Michael Sproul
2019-06-17 18:07:14 +10:00
parent 9a356a00c2
commit 38d2d03e3a
6 changed files with 338 additions and 120 deletions
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139
eth2/operation_pool/src/lib.rs
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@@ -1,7 +1,12 @@
use int_to_bytes::int_to_bytes8;
mod attestation;
mod attestation_id;
mod max_cover;
use attestation::{earliest_attestation_validators, AttMaxCover};
use attestation_id::AttestationId;
use itertools::Itertools;
use max_cover::maximum_cover;
use parking_lot::RwLock;
use ssz::ssz_encode;
use state_processing::per_block_processing::errors::{
AttestationValidationError, AttesterSlashingValidationError, DepositValidationError,
ExitValidationError, ProposerSlashingValidationError, TransferValidationError,
@@ -16,10 +21,9 @@ use state_processing::per_block_processing::{
};
use std::collections::{btree_map::Entry, hash_map, BTreeMap, HashMap, HashSet};
use std::marker::PhantomData;
use types::chain_spec::Domain;
use types::{
Attestation, AttestationData, AttesterSlashing, BeaconState, ChainSpec, Deposit, Epoch,
EthSpec, ProposerSlashing, Transfer, Validator, VoluntaryExit,
Attestation, AttesterSlashing, BeaconState, ChainSpec, Deposit, EthSpec, ProposerSlashing,
Transfer, Validator, VoluntaryExit,
};
#[derive(Default)]
@@ -43,71 +47,6 @@ pub struct OperationPool<T: EthSpec + Default> {
_phantom: PhantomData<T>,
}
/// Serialized `AttestationData` augmented with a domain to encode the fork info.
#[derive(PartialEq, Eq, Clone, Hash, Debug)]
struct AttestationId(Vec<u8>);
/// Number of domain bytes that the end of an attestation ID is padded with.
const DOMAIN_BYTES_LEN: usize = 8;
impl AttestationId {
fn from_data<T: EthSpec>(
attestation: &AttestationData,
state: &BeaconState<T>,
spec: &ChainSpec,
) -> Self {
let mut bytes = ssz_encode(attestation);
let epoch = attestation.target_epoch;
bytes.extend_from_slice(&AttestationId::compute_domain_bytes(epoch, state, spec));
AttestationId(bytes)
}
fn compute_domain_bytes<T: EthSpec>(
epoch: Epoch,
state: &BeaconState<T>,
spec: &ChainSpec,
) -> Vec<u8> {
int_to_bytes8(spec.get_domain(epoch, Domain::Attestation, &state.fork))
}
fn domain_bytes_match(&self, domain_bytes: &[u8]) -> bool {
&self.0[self.0.len() - DOMAIN_BYTES_LEN..] == domain_bytes
}
}
/// Compute a fitness score for an attestation.
///
/// The score is calculated by determining the number of *new* attestations that
/// the aggregate attestation introduces, and is proportional to the size of the reward we will
/// receive for including it in a block.
// TODO: this could be optimised with a map from validator index to whether that validator has
// attested in each of the current and previous epochs. Currently quadractic in number of validators.
fn attestation_score<T: EthSpec>(attestation: &Attestation, state: &BeaconState<T>) -> usize {
// Bitfield of validators whose attestations are new/fresh.
let mut new_validators = attestation.aggregation_bitfield.clone();
let state_attestations = if attestation.data.target_epoch == state.current_epoch() {
&state.current_epoch_attestations
} else if attestation.data.target_epoch == state.previous_epoch() {
&state.previous_epoch_attestations
} else {
return 0;
};
state_attestations
.iter()
// In a single epoch, an attester should only be attesting for one shard.
// TODO: we avoid including slashable attestations in the state here,
// but maybe we should do something else with them (like construct slashings).
.filter(|current_attestation| current_attestation.data.shard == attestation.data.shard)
.for_each(|current_attestation| {
// Remove the validators who have signed the existing attestation (they are not new)
new_validators.difference_inplace(&current_attestation.aggregation_bitfield);
});
new_validators.num_set_bits()
}
#[derive(Debug, PartialEq, Clone)]
pub enum DepositInsertStatus {
/// The deposit was not already in the pool.
@@ -176,29 +115,19 @@ impl<T: EthSpec> OperationPool<T> {
let current_epoch = state.current_epoch();
let prev_domain_bytes = AttestationId::compute_domain_bytes(prev_epoch, state, spec);
let curr_domain_bytes = AttestationId::compute_domain_bytes(current_epoch, state, spec);
self.attestations
.read()
let reader = self.attestations.read();
let valid_attestations = reader
.iter()
.filter(|(key, _)| {
key.domain_bytes_match(&prev_domain_bytes)
|| key.domain_bytes_match(&curr_domain_bytes)
})
.flat_map(|(_, attestations)| attestations)
// That are not superseded by an attestation included in the state...
.filter(|attestation| !superior_attestation_exists_in_state(state, attestation))
// That are valid...
.filter(|attestation| validate_attestation(state, attestation, spec).is_ok())
// Scored by the number of new attestations they introduce (descending)
// TODO: need to consider attestations introduced in THIS block
.map(|att| (att, attestation_score(att, state)))
// Don't include any useless attestations (score 0)
.filter(|&(_, score)| score != 0)
.sorted_by_key(|&(_, score)| std::cmp::Reverse(score))
// Limited to the maximum number of attestations per block
.take(spec.max_attestations as usize)
.map(|(att, _)| att)
.cloned()
.collect()
.map(|att| AttMaxCover::new(att, earliest_attestation_validators(att, state)));
maximum_cover(valid_attestations, spec.max_attestations as usize)
}
/// Remove attestations which are too old to be included in a block.
@@ -484,34 +413,6 @@ impl<T: EthSpec> OperationPool<T> {
}
}
/// Returns `true` if the state already contains a `PendingAttestation` that is superior to the
/// given `attestation`.
///
/// A validator has nothing to gain from re-including an attestation and it adds load to the
/// network.
///
/// An existing `PendingAttestation` is superior to an existing `attestation` if:
///
/// - Their `AttestationData` is equal.
/// - `attestation` does not contain any signatures that `PendingAttestation` does not have.
fn superior_attestation_exists_in_state<T: EthSpec>(
state: &BeaconState<T>,
attestation: &Attestation,
) -> bool {
state
.current_epoch_attestations
.iter()
.chain(state.previous_epoch_attestations.iter())
.any(|existing_attestation| {
let bitfield = &attestation.aggregation_bitfield;
let existing_bitfield = &existing_attestation.aggregation_bitfield;
existing_attestation.data == attestation.data
&& bitfield.intersection(existing_bitfield).num_set_bits()
== bitfield.num_set_bits()
})
}
/// Filter up to a maximum number of operations out of an iterator.
fn filter_limit_operations<'a, T: 'a, I, F>(operations: I, filter: F, limit: u64) -> Vec<T>
where
@@ -734,15 +635,13 @@ mod tests {
state_builder.teleport_to_slot(slot);
state_builder.build_caches(&spec).unwrap();
let (state, keypairs) = state_builder.build();
(state, keypairs, MainnetEthSpec::default_spec())
}
#[test]
fn test_attestation_score() {
fn test_earliest_attestation() {
let (ref mut state, ref keypairs, ref spec) =
attestation_test_state::<MainnetEthSpec>(1);
let slot = state.slot - 1;
let committees = state
.get_crosslink_committees_at_slot(slot)
@@ -775,9 +674,8 @@ mod tests {
assert_eq!(
att1.aggregation_bitfield.num_set_bits(),
attestation_score(&att1, state)
earliest_attestation_validators(&att1, state).num_set_bits()
);
state.current_epoch_attestations.push(PendingAttestation {
aggregation_bitfield: att1.aggregation_bitfield.clone(),
data: att1.data.clone(),
@@ -785,7 +683,10 @@ mod tests {
proposer_index: 0,
});
assert_eq!(cc.committee.len() - 2, attestation_score(&att2, state));
assert_eq!(
cc.committee.len() - 2,
earliest_attestation_validators(&att2, state).num_set_bits()
);
}
}