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Update 0_beacon-chain.md

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Justin 2019-04-14 17:28:45 +10:00 committed by GitHub
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specs/core/0_beacon-chain.md
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@ -184,6 +184,7 @@ These configurations are updated for releases, but may be out of sync during `de
| `TARGET_COMMITTEE_SIZE` | `2**7` (= 128) | | `TARGET_COMMITTEE_SIZE` | `2**7` (= 128) |
| `MAX_ATTESTATION_PARTICIPANTS` | `2**12` (= 4,096) | | `MAX_ATTESTATION_PARTICIPANTS` | `2**12` (= 4,096) |
| `MIN_PER_EPOCH_CHURN_LIMIT` | `2**2` (= 4) | | `MIN_PER_EPOCH_CHURN_LIMIT` | `2**2` (= 4) |
| `CHURN_LIMIT_QUOTIENT` | `2**16` (= 65,536) |
| `SHUFFLE_ROUND_COUNT` | 90 | | `SHUFFLE_ROUND_COUNT` | 90 |
* For the safety of crosslinks `TARGET_COMMITTEE_SIZE` exceeds [the recommended minimum committee size of 111](https://vitalik.ca/files/Ithaca201807_Sharding.pdf); with sufficient active validators (at least `SLOTS_PER_EPOCH * TARGET_COMMITTEE_SIZE`), the shuffling algorithm ensures committee sizes of at least `TARGET_COMMITTEE_SIZE`. (Unbiasable randomness with a Verifiable Delay Function (VDF) will improve committee robustness and lower the safe minimum committee size.) * For the safety of crosslinks `TARGET_COMMITTEE_SIZE` exceeds [the recommended minimum committee size of 111](https://vitalik.ca/files/Ithaca201807_Sharding.pdf); with sufficient active validators (at least `SLOTS_PER_EPOCH * TARGET_COMMITTEE_SIZE`), the shuffling algorithm ensures committee sizes of at least `TARGET_COMMITTEE_SIZE`. (Unbiasable randomness with a Verifiable Delay Function (VDF) will improve committee robustness and lower the safe minimum committee size.)
@ -237,7 +238,6 @@ These configurations are updated for releases, but may be out of sync during `de
* `MAX_CROSSLINK_EPOCHS` should be a small constant times `SHARD_COUNT // SLOTS_PER_EPOCH` * `MAX_CROSSLINK_EPOCHS` should be a small constant times `SHARD_COUNT // SLOTS_PER_EPOCH`
### State list lengths ### State list lengths
| Name | Value | Unit | Duration | | Name | Value | Unit | Duration |
@ -746,11 +746,11 @@ def is_slashable_validator(validator: Validator, epoch: Epoch) -> bool:
### `get_active_validator_indices` ### `get_active_validator_indices`
```python ```python
def get_active_validator_indices(validators: List[Validator], epoch: Epoch) -> List[ValidatorIndex]: def get_active_validator_indices(state: BeaconState, epoch: Epoch) -> List[ValidatorIndex]:
""" """
Get indices of active validators from ``validators``. Get active validator indices at ``epoch``.
""" """
return [i for i, v in enumerate(validators) if is_active_validator(v, epoch)] return [i for i, v in enumerate(state.validator_registry) if is_active_validator(v, epoch)]
``` ```
### `get_balance` ### `get_balance`
@ -844,7 +844,7 @@ def get_epoch_committee_count(state: BeaconState, epoch: Epoch) -> int:
""" """
Return the number of committees in one epoch. Return the number of committees in one epoch.
""" """
active_validators = get_active_validator_indices(state.validator_registry, epoch) active_validators = get_active_validator_indices(state, epoch)
return max( return max(
1, 1,
min( min(
@ -896,10 +896,7 @@ def get_crosslink_committees_at_slot(state: BeaconState,
next_epoch = current_epoch + 1 next_epoch = current_epoch + 1
assert previous_epoch <= epoch <= next_epoch assert previous_epoch <= epoch <= next_epoch
indices = get_active_validator_indices( indices = get_active_validator_indices(state, epoch)
state.validator_registry,
epoch,
)
if epoch == current_epoch: if epoch == current_epoch:
start_shard = state.latest_start_shard start_shard = state.latest_start_shard
@ -1276,7 +1273,7 @@ def get_delayed_activation_exit_epoch(epoch: Epoch) -> Epoch:
def get_churn_limit(state: BeaconState) -> int: def get_churn_limit(state: BeaconState) -> int:
return max( return max(
MIN_PER_EPOCH_CHURN_LIMIT, MIN_PER_EPOCH_CHURN_LIMIT,
MAX_FULL_CHURN_EPOCHS // len(get_active_validator_indices(state, get_current_epoch(state))) len(get_active_validator_indices(state, get_current_epoch(state))) // CHURN_LIMIT_QUOTIENT
) )
``` ```
@ -1517,7 +1514,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
if get_effective_balance(state, validator_index) >= MAX_DEPOSIT_AMOUNT: if get_effective_balance(state, validator_index) >= MAX_DEPOSIT_AMOUNT:
activate_validator(state, validator_index, is_genesis=True) activate_validator(state, validator_index, is_genesis=True)
genesis_active_index_root = hash_tree_root(get_active_validator_indices(state.validator_registry, GENESIS_EPOCH)) genesis_active_index_root = hash_tree_root(get_active_validator_indices(state, GENESIS_EPOCH))
for index in range(LATEST_ACTIVE_INDEX_ROOTS_LENGTH): for index in range(LATEST_ACTIVE_INDEX_ROOTS_LENGTH):
state.latest_active_index_roots[index] = genesis_active_index_root state.latest_active_index_roots[index] = genesis_active_index_root
@ -1651,12 +1648,12 @@ We define some helper functions utilized when processing an epoch transition:
```python ```python
def get_current_total_balance(state: BeaconState) -> Gwei: def get_current_total_balance(state: BeaconState) -> Gwei:
return get_total_balance(state, get_active_validator_indices(state.validator_registry, get_current_epoch(state))) return get_total_balance(state, get_active_validator_indices(state, get_current_epoch(state)))
``` ```
```python ```python
def get_previous_total_balance(state: BeaconState) -> Gwei: def get_previous_total_balance(state: BeaconState) -> Gwei:
return get_total_balance(state, get_active_validator_indices(state.validator_registry, get_previous_epoch(state))) return get_total_balance(state, get_active_validator_indices(state, get_previous_epoch(state)))
``` ```
```python ```python
@ -1994,7 +1991,7 @@ def process_slashings(state: BeaconState) -> None:
Note that this function mutates ``state``. Note that this function mutates ``state``.
""" """
current_epoch = get_current_epoch(state) current_epoch = get_current_epoch(state)
active_validator_indices = get_active_validator_indices(state.validator_registry, current_epoch) active_validator_indices = get_active_validator_indices(state, current_epoch)
total_balance = get_total_balance(state, active_validator_indices) total_balance = get_total_balance(state, active_validator_indices)
# Compute `total_penalties` # Compute `total_penalties`
@ -2022,7 +2019,7 @@ def finish_epoch_update(state: BeaconState) -> None:
# Set active index root # Set active index root
index_root_position = (next_epoch + ACTIVATION_EXIT_DELAY) % LATEST_ACTIVE_INDEX_ROOTS_LENGTH index_root_position = (next_epoch + ACTIVATION_EXIT_DELAY) % LATEST_ACTIVE_INDEX_ROOTS_LENGTH
state.latest_active_index_roots[index_root_position] = hash_tree_root( state.latest_active_index_roots[index_root_position] = hash_tree_root(
get_active_validator_indices(state.validator_registry, next_epoch + ACTIVATION_EXIT_DELAY) get_active_validator_indices(state, next_epoch + ACTIVATION_EXIT_DELAY)
) )
# Set total slashed balances # Set total slashed balances
state.latest_slashed_balances[next_epoch % LATEST_SLASHED_EXIT_LENGTH] = ( state.latest_slashed_balances[next_epoch % LATEST_SLASHED_EXIT_LENGTH] = (