31 KiB
31 KiB
Altair -- The Beacon Chain
Table of contents
- Introduction
- Custom types
- Constants
- Preset
- Configuration
- Containers
- Helper functions
- Initialize state for pure Altair testnets and test vectors
Introduction
Altair is the first beacon chain hard fork. Its main features are:
- sync committees to support light clients
- incentive accounting reforms to reduce spec complexity
- penalty parameter updates towards their planned maximally punitive values
Custom types
| Name | SSZ equivalent | Description |
|---|---|---|
ParticipationFlags |
uint8 |
a succinct representation of 8 boolean participation flags |
Constants
Participation flag indices
| Name | Value |
|---|---|
TIMELY_SOURCE_FLAG_INDEX |
0 |
TIMELY_TARGET_FLAG_INDEX |
1 |
TIMELY_HEAD_FLAG_INDEX |
2 |
Incentivization weights
| Name | Value |
|---|---|
TIMELY_SOURCE_WEIGHT |
uint64(14) |
TIMELY_TARGET_WEIGHT |
uint64(26) |
TIMELY_HEAD_WEIGHT |
uint64(14) |
SYNC_REWARD_WEIGHT |
uint64(2) |
PROPOSER_WEIGHT |
uint64(8) |
WEIGHT_DENOMINATOR |
uint64(64) |
Note: The sum of the weights equal WEIGHT_DENOMINATOR.
Domain types
| Name | Value |
|---|---|
DOMAIN_SYNC_COMMITTEE |
DomainType('0x07000000') |
DOMAIN_SYNC_COMMITTEE_SELECTION_PROOF |
DomainType('0x08000000') |
DOMAIN_CONTRIBUTION_AND_PROOF |
DomainType('0x09000000') |
Misc
| Name | Value |
|---|---|
PARTICIPATION_FLAG_WEIGHTS |
[TIMELY_SOURCE_WEIGHT, TIMELY_TARGET_WEIGHT, TIMELY_HEAD_WEIGHT] |
Preset
Updated penalty values
This patch updates a few configuration values to move penalty parameters closer to their final, maximum security values.
Note: The spec does not override previous configuration values but instead creates new values and replaces usage throughout.
| Name | Value |
|---|---|
INACTIVITY_PENALTY_QUOTIENT_ALTAIR |
uint64(3 * 2**24) (= 50,331,648) |
MIN_SLASHING_PENALTY_QUOTIENT_ALTAIR |
uint64(2**6) (= 64) |
PROPORTIONAL_SLASHING_MULTIPLIER_ALTAIR |
uint64(2) |
Sync committee
| Name | Value | Unit | Duration |
|---|---|---|---|
SYNC_COMMITTEE_SIZE |
uint64(2**9) (= 512) |
validators | |
EPOCHS_PER_SYNC_COMMITTEE_PERIOD |
uint64(2**8) (= 256) |
epochs | ~27 hours |
Configuration
Inactivity penalties
| Name | Value | Description |
|---|---|---|
INACTIVITY_SCORE_BIAS |
uint64(2**2) (= 4) |
score points per inactive epoch |
INACTIVITY_SCORE_RECOVERY_RATE |
uint64(2**4) (= 16) |
score points per leak-free epoch |
Containers
Modified containers
BeaconBlockBody
class BeaconBlockBody(Container):
randao_reveal: BLSSignature
eth1_data: Eth1Data # Eth1 data vote
graffiti: Bytes32 # Arbitrary data
# Operations
proposer_slashings: List[ProposerSlashing, MAX_PROPOSER_SLASHINGS]
attester_slashings: List[AttesterSlashing, MAX_ATTESTER_SLASHINGS]
attestations: List[Attestation, MAX_ATTESTATIONS]
deposits: List[Deposit, MAX_DEPOSITS]
voluntary_exits: List[SignedVoluntaryExit, MAX_VOLUNTARY_EXITS]
sync_aggregate: SyncAggregate # [New in Altair]
BeaconState
class BeaconState(Container):
# Versioning
genesis_time: uint64
genesis_validators_root: Root
slot: Slot
fork: Fork
# History
latest_block_header: BeaconBlockHeader
block_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
state_roots: Vector[Root, SLOTS_PER_HISTORICAL_ROOT]
historical_roots: List[Root, HISTORICAL_ROOTS_LIMIT]
# Eth1
eth1_data: Eth1Data
eth1_data_votes: List[Eth1Data, EPOCHS_PER_ETH1_VOTING_PERIOD * SLOTS_PER_EPOCH]
eth1_deposit_index: uint64
# Registry
validators: List[Validator, VALIDATOR_REGISTRY_LIMIT]
balances: List[Gwei, VALIDATOR_REGISTRY_LIMIT]
# Randomness
randao_mixes: Vector[Bytes32, EPOCHS_PER_HISTORICAL_VECTOR]
# Slashings
slashings: Vector[Gwei, EPOCHS_PER_SLASHINGS_VECTOR] # Per-epoch sums of slashed effective balances
# Participation
previous_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [Modified in Altair]
current_epoch_participation: List[ParticipationFlags, VALIDATOR_REGISTRY_LIMIT] # [Modified in Altair]
# Finality
justification_bits: Bitvector[JUSTIFICATION_BITS_LENGTH] # Bit set for every recent justified epoch
previous_justified_checkpoint: Checkpoint
current_justified_checkpoint: Checkpoint
finalized_checkpoint: Checkpoint
# Inactivity
inactivity_scores: List[uint64, VALIDATOR_REGISTRY_LIMIT] # [New in Altair]
# Sync
current_sync_committee: SyncCommittee # [New in Altair]
next_sync_committee: SyncCommittee # [New in Altair]
New containers
SyncAggregate
class SyncAggregate(Container):
sync_committee_bits: Bitvector[SYNC_COMMITTEE_SIZE]
sync_committee_signature: BLSSignature
SyncCommittee
class SyncCommittee(Container):
pubkeys: Vector[BLSPubkey, SYNC_COMMITTEE_SIZE]
aggregate_pubkey: BLSPubkey
Helper functions
Crypto
Refer to the definitions in the phase 0 document regarding BLS signatures and the extensions defined in the Altair BLS document. This specification assumes knowledge of the functionality described in those documents.
Misc
add_flag
def add_flag(flags: ParticipationFlags, flag_index: int) -> ParticipationFlags:
"""
Return a new ``ParticipationFlags`` adding ``flag_index`` to ``flags``.
"""
flag = ParticipationFlags(2**flag_index)
return flags | flag
has_flag
def has_flag(flags: ParticipationFlags, flag_index: int) -> bool:
"""
Return whether ``flags`` has ``flag_index`` set.
"""
flag = ParticipationFlags(2**flag_index)
return flags & flag == flag
get_index_for_new_validator
def get_index_for_new_validator(state: BeaconState) -> ValidatorIndex:
return ValidatorIndex(len(state.validators))
set_or_append_list
def set_or_append_list(list: List, index: ValidatorIndex, value: Any) -> None:
if index == len(list):
list.append(value)
else:
list[index] = value
Beacon state accessors
get_next_sync_committee_indices
def get_next_sync_committee_indices(state: BeaconState) -> Sequence[ValidatorIndex]:
"""
Return the sync committee indices, with possible duplicates, for the next sync committee.
"""
epoch = Epoch(get_current_epoch(state) + 1)
MAX_RANDOM_BYTE = 2**8 - 1
active_validator_indices = get_active_validator_indices(state, epoch)
active_validator_count = uint64(len(active_validator_indices))
seed = get_seed(state, epoch, DOMAIN_SYNC_COMMITTEE)
i = 0
sync_committee_indices: List[ValidatorIndex] = []
while len(sync_committee_indices) < SYNC_COMMITTEE_SIZE:
shuffled_index = compute_shuffled_index(uint64(i % active_validator_count), active_validator_count, seed)
candidate_index = active_validator_indices[shuffled_index]
random_byte = hash(seed + uint_to_bytes(uint64(i // 32)))[i % 32]
effective_balance = state.validators[candidate_index].effective_balance
if effective_balance * MAX_RANDOM_BYTE >= MAX_EFFECTIVE_BALANCE * random_byte:
sync_committee_indices.append(candidate_index)
i += 1
return sync_committee_indices
get_next_sync_committee
Note: The function get_next_sync_committee should only be called at sync committee period boundaries and when upgrading state to Altair.
def get_next_sync_committee(state: BeaconState) -> SyncCommittee:
"""
Return the next sync committee, with possible pubkey duplicates.
"""
indices = get_next_sync_committee_indices(state)
pubkeys = [state.validators[index].pubkey for index in indices]
aggregate_pubkey = eth_aggregate_pubkeys(pubkeys)
return SyncCommittee(pubkeys=pubkeys, aggregate_pubkey=aggregate_pubkey)
get_base_reward_per_increment
def get_base_reward_per_increment(state: BeaconState) -> Gwei:
return Gwei(EFFECTIVE_BALANCE_INCREMENT * BASE_REWARD_FACTOR // integer_squareroot(get_total_active_balance(state)))
get_base_reward
Note: The function get_base_reward is modified with the removal of BASE_REWARDS_PER_EPOCH and the use of increment based accounting.
Note: On average an optimally performing validator earns one base reward per epoch.
def get_base_reward(state: BeaconState, index: ValidatorIndex) -> Gwei:
"""
Return the base reward for the validator defined by ``index`` with respect to the current ``state``.
"""
increments = state.validators[index].effective_balance // EFFECTIVE_BALANCE_INCREMENT
return Gwei(increments * get_base_reward_per_increment(state))
get_unslashed_participating_indices
def get_unslashed_participating_indices(state: BeaconState, flag_index: int, epoch: Epoch) -> Set[ValidatorIndex]:
"""
Return the set of validator indices that are both active and unslashed for the given ``flag_index`` and ``epoch``.
"""
assert epoch in (get_previous_epoch(state), get_current_epoch(state))
if epoch == get_current_epoch(state):
epoch_participation = state.current_epoch_participation
else:
epoch_participation = state.previous_epoch_participation
active_validator_indices = get_active_validator_indices(state, epoch)
participating_indices = [i for i in active_validator_indices if has_flag(epoch_participation[i], flag_index)]
return set(filter(lambda index: not state.validators[index].slashed, participating_indices))
get_attestation_participation_flag_indices
def get_attestation_participation_flag_indices(state: BeaconState,
data: AttestationData,
inclusion_delay: uint64) -> Sequence[int]:
"""
Return the flag indices that are satisfied by an attestation.
"""
if data.target.epoch == get_current_epoch(state):
justified_checkpoint = state.current_justified_checkpoint
else:
justified_checkpoint = state.previous_justified_checkpoint
# Matching roots
is_matching_source = data.source == justified_checkpoint
is_matching_target = is_matching_source and data.target.root == get_block_root(state, data.target.epoch)
is_matching_head = is_matching_target and data.beacon_block_root == get_block_root_at_slot(state, data.slot)
assert is_matching_source
participation_flag_indices = []
if is_matching_source and inclusion_delay <= integer_squareroot(SLOTS_PER_EPOCH):
participation_flag_indices.append(TIMELY_SOURCE_FLAG_INDEX)
if is_matching_target and inclusion_delay <= SLOTS_PER_EPOCH:
participation_flag_indices.append(TIMELY_TARGET_FLAG_INDEX)
if is_matching_head and inclusion_delay == MIN_ATTESTATION_INCLUSION_DELAY:
participation_flag_indices.append(TIMELY_HEAD_FLAG_INDEX)
return participation_flag_indices
get_flag_index_deltas
def get_flag_index_deltas(state: BeaconState, flag_index: int) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
"""
Return the deltas for a given ``flag_index`` by scanning through the participation flags.
"""
rewards = [Gwei(0)] * len(state.validators)
penalties = [Gwei(0)] * len(state.validators)
previous_epoch = get_previous_epoch(state)
unslashed_participating_indices = get_unslashed_participating_indices(state, flag_index, previous_epoch)
weight = PARTICIPATION_FLAG_WEIGHTS[flag_index]
unslashed_participating_balance = get_total_balance(state, unslashed_participating_indices)
unslashed_participating_increments = unslashed_participating_balance // EFFECTIVE_BALANCE_INCREMENT
active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
for index in get_eligible_validator_indices(state):
base_reward = get_base_reward(state, index)
if index in unslashed_participating_indices:
if not is_in_inactivity_leak(state):
reward_numerator = base_reward * weight * unslashed_participating_increments
rewards[index] += Gwei(reward_numerator // (active_increments * WEIGHT_DENOMINATOR))
elif flag_index != TIMELY_HEAD_FLAG_INDEX:
penalties[index] += Gwei(base_reward * weight // WEIGHT_DENOMINATOR)
return rewards, penalties
Modified get_inactivity_penalty_deltas
def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], Sequence[Gwei]]:
"""
Return the inactivity penalty deltas by considering timely target participation flags and inactivity scores.
"""
rewards = [Gwei(0) for _ in range(len(state.validators))]
penalties = [Gwei(0) for _ in range(len(state.validators))]
previous_epoch = get_previous_epoch(state)
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
for index in get_eligible_validator_indices(state):
if index not in matching_target_indices:
penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
penalties[index] += Gwei(penalty_numerator // penalty_denominator)
return rewards, penalties
Beacon state mutators
Modified slash_validator
Note: The function slash_validator is modified to use MIN_SLASHING_PENALTY_QUOTIENT_ALTAIR
and use PROPOSER_WEIGHT when calculating the proposer reward.
def slash_validator(state: BeaconState,
slashed_index: ValidatorIndex,
whistleblower_index: ValidatorIndex=None) -> None:
"""
Slash the validator with index ``slashed_index``.
"""
epoch = get_current_epoch(state)
initiate_validator_exit(state, slashed_index)
validator = state.validators[slashed_index]
validator.slashed = True
validator.withdrawable_epoch = max(validator.withdrawable_epoch, Epoch(epoch + EPOCHS_PER_SLASHINGS_VECTOR))
state.slashings[epoch % EPOCHS_PER_SLASHINGS_VECTOR] += validator.effective_balance
decrease_balance(state, slashed_index, validator.effective_balance // MIN_SLASHING_PENALTY_QUOTIENT_ALTAIR)
# Apply proposer and whistleblower rewards
proposer_index = get_beacon_proposer_index(state)
if whistleblower_index is None:
whistleblower_index = proposer_index
whistleblower_reward = Gwei(validator.effective_balance // WHISTLEBLOWER_REWARD_QUOTIENT)
proposer_reward = Gwei(whistleblower_reward * PROPOSER_WEIGHT // WEIGHT_DENOMINATOR)
increase_balance(state, proposer_index, proposer_reward)
increase_balance(state, whistleblower_index, Gwei(whistleblower_reward - proposer_reward))
Block processing
def process_block(state: BeaconState, block: BeaconBlock) -> None:
process_block_header(state, block)
process_randao(state, block.body)
process_eth1_data(state, block.body)
process_operations(state, block.body) # [Modified in Altair]
process_sync_aggregate(state, block.body.sync_aggregate) # [New in Altair]
Modified process_attestation
Note: The function process_attestation is modified to do incentive accounting with epoch participation flags.
def process_attestation(state: BeaconState, attestation: Attestation) -> None:
data = attestation.data
assert data.target.epoch in (get_previous_epoch(state), get_current_epoch(state))
assert data.target.epoch == compute_epoch_at_slot(data.slot)
assert data.slot + MIN_ATTESTATION_INCLUSION_DELAY <= state.slot <= data.slot + SLOTS_PER_EPOCH
assert data.index < get_committee_count_per_slot(state, data.target.epoch)
committee = get_beacon_committee(state, data.slot, data.index)
assert len(attestation.aggregation_bits) == len(committee)
# Participation flag indices
participation_flag_indices = get_attestation_participation_flag_indices(state, data, state.slot - data.slot)
# Verify signature
assert is_valid_indexed_attestation(state, get_indexed_attestation(state, attestation))
# Update epoch participation flags
if data.target.epoch == get_current_epoch(state):
epoch_participation = state.current_epoch_participation
else:
epoch_participation = state.previous_epoch_participation
proposer_reward_numerator = 0
for index in get_attesting_indices(state, data, attestation.aggregation_bits):
for flag_index, weight in enumerate(PARTICIPATION_FLAG_WEIGHTS):
if flag_index in participation_flag_indices and not has_flag(epoch_participation[index], flag_index):
epoch_participation[index] = add_flag(epoch_participation[index], flag_index)
proposer_reward_numerator += get_base_reward(state, index) * weight
# Reward proposer
proposer_reward_denominator = (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT) * WEIGHT_DENOMINATOR // PROPOSER_WEIGHT
proposer_reward = Gwei(proposer_reward_numerator // proposer_reward_denominator)
increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
Modified apply_deposit
Note: The function apply_deposit is modified to initialize inactivity_scores, previous_epoch_participation, and current_epoch_participation.
def apply_deposit(state: BeaconState,
pubkey: BLSPubkey,
withdrawal_credentials: Bytes32,
amount: uint64,
signature: BLSSignature) -> None:
validator_pubkeys = [validator.pubkey for validator in state.validators]
if pubkey not in validator_pubkeys:
# Verify the deposit signature (proof of possession) which is not checked by the deposit contract
deposit_message = DepositMessage(
pubkey=pubkey,
withdrawal_credentials=withdrawal_credentials,
amount=amount,
)
domain = compute_domain(DOMAIN_DEPOSIT) # Fork-agnostic domain since deposits are valid across forks
signing_root = compute_signing_root(deposit_message, domain)
# Initialize validator if the deposit signature is valid
if bls.Verify(pubkey, signing_root, signature):
index = get_index_for_new_validator(state)
validator = get_validator_from_deposit(pubkey, withdrawal_credentials, amount)
set_or_append_list(state.validators, index, validator)
set_or_append_list(state.balances, index, amount)
# [New in Altair]
set_or_append_list(state.previous_epoch_participation, index, ParticipationFlags(0b0000_0000))
set_or_append_list(state.current_epoch_participation, index, ParticipationFlags(0b0000_0000))
set_or_append_list(state.inactivity_scores, index, uint64(0))
else:
# Increase balance by deposit amount
index = ValidatorIndex(validator_pubkeys.index(pubkey))
increase_balance(state, index, amount)
Sync aggregate processing
Note: The function process_sync_aggregate is new.
def process_sync_aggregate(state: BeaconState, sync_aggregate: SyncAggregate) -> None:
# Verify sync committee aggregate signature signing over the previous slot block root
committee_pubkeys = state.current_sync_committee.pubkeys
participant_pubkeys = [pubkey for pubkey, bit in zip(committee_pubkeys, sync_aggregate.sync_committee_bits) if bit]
previous_slot = max(state.slot, Slot(1)) - Slot(1)
domain = get_domain(state, DOMAIN_SYNC_COMMITTEE, compute_epoch_at_slot(previous_slot))
signing_root = compute_signing_root(get_block_root_at_slot(state, previous_slot), domain)
assert eth_fast_aggregate_verify(participant_pubkeys, signing_root, sync_aggregate.sync_committee_signature)
# Compute participant and proposer rewards
total_active_increments = get_total_active_balance(state) // EFFECTIVE_BALANCE_INCREMENT
total_base_rewards = Gwei(get_base_reward_per_increment(state) * total_active_increments)
max_participant_rewards = Gwei(total_base_rewards * SYNC_REWARD_WEIGHT // WEIGHT_DENOMINATOR // SLOTS_PER_EPOCH)
participant_reward = Gwei(max_participant_rewards // SYNC_COMMITTEE_SIZE)
proposer_reward = Gwei(participant_reward * PROPOSER_WEIGHT // (WEIGHT_DENOMINATOR - PROPOSER_WEIGHT))
# Apply participant and proposer rewards
all_pubkeys = [v.pubkey for v in state.validators]
committee_indices = [ValidatorIndex(all_pubkeys.index(pubkey)) for pubkey in state.current_sync_committee.pubkeys]
for participant_index, participation_bit in zip(committee_indices, sync_aggregate.sync_committee_bits):
if participation_bit:
increase_balance(state, participant_index, participant_reward)
increase_balance(state, get_beacon_proposer_index(state), proposer_reward)
else:
decrease_balance(state, participant_index, participant_reward)
Epoch processing
def process_epoch(state: BeaconState) -> None:
process_justification_and_finalization(state) # [Modified in Altair]
process_inactivity_updates(state) # [New in Altair]
process_rewards_and_penalties(state) # [Modified in Altair]
process_registry_updates(state)
process_slashings(state) # [Modified in Altair]
process_eth1_data_reset(state)
process_effective_balance_updates(state)
process_slashings_reset(state)
process_randao_mixes_reset(state)
process_historical_roots_update(state)
process_participation_flag_updates(state) # [New in Altair]
process_sync_committee_updates(state) # [New in Altair]
Justification and finalization
Note: The function process_justification_and_finalization is modified to adapt to the new participation records.
def process_justification_and_finalization(state: BeaconState) -> None:
# Initial FFG checkpoint values have a `0x00` stub for `root`.
# Skip FFG updates in the first two epochs to avoid corner cases that might result in modifying this stub.
if get_current_epoch(state) <= GENESIS_EPOCH + 1:
return
previous_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state))
current_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_current_epoch(state))
total_active_balance = get_total_active_balance(state)
previous_target_balance = get_total_balance(state, previous_indices)
current_target_balance = get_total_balance(state, current_indices)
weigh_justification_and_finalization(state, total_active_balance, previous_target_balance, current_target_balance)
Inactivity scores
Note: The function process_inactivity_updates is new.
def process_inactivity_updates(state: BeaconState) -> None:
# Skip the genesis epoch as score updates are based on the previous epoch participation
if get_current_epoch(state) == GENESIS_EPOCH:
return
for index in get_eligible_validator_indices(state):
# Increase the inactivity score of inactive validators
if index in get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)):
state.inactivity_scores[index] -= min(1, state.inactivity_scores[index])
else:
state.inactivity_scores[index] += INACTIVITY_SCORE_BIAS
# Decrease the inactivity score of all eligible validators during a leak-free epoch
if not is_in_inactivity_leak(state):
state.inactivity_scores[index] -= min(INACTIVITY_SCORE_RECOVERY_RATE, state.inactivity_scores[index])
Rewards and penalties
Note: The function process_rewards_and_penalties is modified to support the incentive accounting reforms.
def process_rewards_and_penalties(state: BeaconState) -> None:
# No rewards are applied at the end of `GENESIS_EPOCH` because rewards are for work done in the previous epoch
if get_current_epoch(state) == GENESIS_EPOCH:
return
flag_deltas = [get_flag_index_deltas(state, flag_index) for flag_index in range(len(PARTICIPATION_FLAG_WEIGHTS))]
deltas = flag_deltas + [get_inactivity_penalty_deltas(state)]
for (rewards, penalties) in deltas:
for index in range(len(state.validators)):
increase_balance(state, ValidatorIndex(index), rewards[index])
decrease_balance(state, ValidatorIndex(index), penalties[index])
Slashings
Note: The function process_slashings is modified to use PROPORTIONAL_SLASHING_MULTIPLIER_ALTAIR.
def process_slashings(state: BeaconState) -> None:
epoch = get_current_epoch(state)
total_balance = get_total_active_balance(state)
adjusted_total_slashing_balance = min(sum(state.slashings) * PROPORTIONAL_SLASHING_MULTIPLIER_ALTAIR, total_balance)
for index, validator in enumerate(state.validators):
if validator.slashed and epoch + EPOCHS_PER_SLASHINGS_VECTOR // 2 == validator.withdrawable_epoch:
increment = EFFECTIVE_BALANCE_INCREMENT # Factored out from penalty numerator to avoid uint64 overflow
penalty_numerator = validator.effective_balance // increment * adjusted_total_slashing_balance
penalty = penalty_numerator // total_balance * increment
decrease_balance(state, ValidatorIndex(index), penalty)
Participation flags updates
Note: The function process_participation_flag_updates is new.
def process_participation_flag_updates(state: BeaconState) -> None:
state.previous_epoch_participation = state.current_epoch_participation
state.current_epoch_participation = [ParticipationFlags(0b0000_0000) for _ in range(len(state.validators))]
Sync committee updates
Note: The function process_sync_committee_updates is new.
def process_sync_committee_updates(state: BeaconState) -> None:
next_epoch = get_current_epoch(state) + Epoch(1)
if next_epoch % EPOCHS_PER_SYNC_COMMITTEE_PERIOD == 0:
state.current_sync_committee = state.next_sync_committee
state.next_sync_committee = get_next_sync_committee(state)
Initialize state for pure Altair testnets and test vectors
This helper function is only for initializing the state for pure Altair testnets and tests.
Note: The function initialize_beacon_state_from_eth1 is modified: (1) using ALTAIR_FORK_VERSION as the previous and current fork version, (2) utilizing the Altair BeaconBlockBody when constructing the initial latest_block_header, and (3) adding initial sync committees.
def initialize_beacon_state_from_eth1(eth1_block_hash: Hash32,
eth1_timestamp: uint64,
deposits: Sequence[Deposit]) -> BeaconState:
fork = Fork(
previous_version=ALTAIR_FORK_VERSION, # [Modified in Altair] for testing only
current_version=ALTAIR_FORK_VERSION, # [Modified in Altair]
epoch=GENESIS_EPOCH,
)
state = BeaconState(
genesis_time=eth1_timestamp + GENESIS_DELAY,
fork=fork,
eth1_data=Eth1Data(block_hash=eth1_block_hash, deposit_count=uint64(len(deposits))),
latest_block_header=BeaconBlockHeader(body_root=hash_tree_root(BeaconBlockBody())),
randao_mixes=[eth1_block_hash] * EPOCHS_PER_HISTORICAL_VECTOR, # Seed RANDAO with Eth1 entropy
)
# Process deposits
leaves = list(map(lambda deposit: deposit.data, deposits))
for index, deposit in enumerate(deposits):
deposit_data_list = List[DepositData, 2**DEPOSIT_CONTRACT_TREE_DEPTH](*leaves[:index + 1])
state.eth1_data.deposit_root = hash_tree_root(deposit_data_list)
process_deposit(state, deposit)
# Process activations
for index, validator in enumerate(state.validators):
balance = state.balances[index]
validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
if validator.effective_balance == MAX_EFFECTIVE_BALANCE:
validator.activation_eligibility_epoch = GENESIS_EPOCH
validator.activation_epoch = GENESIS_EPOCH
# Set genesis validators root for domain separation and chain versioning
state.genesis_validators_root = hash_tree_root(state.validators)
# [New in Altair] Fill in sync committees
# Note: A duplicate committee is assigned for the current and next committee at genesis
state.current_sync_committee = get_next_sync_committee(state)
state.next_sync_committee = get_next_sync_committee(state)
return state