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Justin fixes

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vbuterin 2019-03-19 11:21:17 -05:00 committed by GitHub
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specs/core/0_beacon-chain.md
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@ -183,10 +183,8 @@ Code snippets appearing in `this style` are to be interpreted as Python code.
| `MAX_INDICES_PER_SLASHABLE_VOTE` | `2**12` (= 4,096) |
| `MAX_EXIT_DEQUEUES_PER_EPOCH` | `2**2` (= 4) |
| `SHUFFLE_ROUND_COUNT` | 90 |
| `MAX_CROSSLINK_EPOCHS` | `2**6` (= 64) |
* 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.)
* `MAX_CROSSLINK_EPOCHS` should be a small constant times `SHARD_COUNT // EPOCH_LENGTH`
### Deposit contract
@ -232,6 +230,10 @@ Code snippets appearing in `this style` are to be interpreted as Python code.
| `SLOTS_PER_HISTORICAL_ROOT` | `2**13` (= 8,192) | slots | ~13 hours |
| `MIN_VALIDATOR_WITHDRAWABILITY_DELAY` | `2**8` (= 256) | epochs | ~27 hours |
| `PERSISTENT_COMMITTEE_PERIOD` | `2**11` (= 2,048) | epochs | 9 days |
| `MAX_CROSSLINK_EPOCHS` | `2**6` (= 64) |
* `MAX_CROSSLINK_EPOCHS` should be a small constant times `SHARD_COUNT // SLOTS_PER_EPOCH`
### State list lengths
@ -598,7 +600,7 @@ The types are defined topologically to aid in facilitating an executable version
# Randomness and committees
'latest_randao_mixes': ['bytes32', LATEST_RANDAO_MIXES_LENGTH],
'current_shuffling_start_shard': 'uint64',
'latest_start_shard': 'uint64',
# Finality
'previous_epoch_attestations': [PendingAttestation],
@ -859,15 +861,15 @@ def get_crosslink_committees_at_slot(state: BeaconState,
))
if epoch == current_epoch:
shuffling_start_shard = state.current_shuffling_start_shard
shuffling_start_shard = state.latest_start_shard
elif epoch == previous_epoch:
shuffling_start_shard = (
state.current_shuffling_start_shard - EPOCH_LENGTH * committees_per_epoch
state.latest_start_shard - SLOTS_PER_EPOCH * committees_per_epoch
) % SHARD_COUNT
elif epoch == next_epoch:
current_epoch_committees = get_current_epoch_committee_count(state)
shuffling_start_shard = (
state.current_shuffling_start_shard + EPOCH_LENGTH * current_epoch_committees
state.latest_start_shard + EPOCH_LENGTH * current_epoch_committees
) % SHARD_COUNT
shuffling = get_shuffling(
@ -1483,7 +1485,7 @@ def get_genesis_beacon_state(genesis_validator_deposits: List[Deposit],
# Randomness and committees
latest_randao_mixes=Vector([ZERO_HASH for _ in range(LATEST_RANDAO_MIXES_LENGTH)]),
current_shuffling_start_shard=GENESIS_START_SHARD,
latest_start_shard=GENESIS_START_SHARD,
# Finality
previous_epoch_attestations=[],
@ -2003,14 +2005,6 @@ def process_ejections(state: BeaconState) -> None:
#### Validator registry and shuffling seed data
```python
def should_update_validator_registry(state: BeaconState) -> bool:
# Must have finalized a new block
if state.finalized_epoch <= state.validator_registry_update_epoch:
return False
return True
```
```python
def update_validator_registry(state: BeaconState) -> None:
"""
@ -2060,16 +2054,13 @@ Run the following function:
```python
def update_registry(state: BeaconState) -> None:
current_epoch = get_current_epoch(state)
next_epoch = current_epoch + 1
# Check if we should update, and if so, update
if should_update_validator_registry(state):
if state.finalized_epoch > state.validator_registry_update_epoch:
update_validator_registry(state)
# If we update the registry, update the shuffling data 2/3 or and shards as well
state.current_shuffling_start_shard = (
state.current_shuffling_start_shard +
get_current_epoch_committee_count(state) % SHARD_COUNT
)
state.latest_start_shard = (
state.latest_start_shard +
get_current_epoch_committee_count(state)
) % SHARD_COUNT
```
**Invariant**: the active index root that is hashed into the shuffling seed actually is the `hash_tree_root` of the validator set that is used for that epoch.