prev -> previous, cur -> current, get_shard_committee_at_slot rework, get_randao_mix rework
This commit is contained in:
Vitalik Buterin
parent
0b16430cf5
commit
e2886bf3d3
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@ -67,10 +67,11 @@
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- [`split`](#split)
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- [`get_committees_per_slot`](#get_committees_per_slot)
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- [`get_shuffling`](#get_shuffling)
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- [`get_prev_epoch_committees_per_slot`](#get_prev_epoch_committees_per_slot)
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- [`get_cur_epoch_committees_per_slot`](#get_cur_epoch_committees_per_slot)
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- [`get_previous_epoch_committees_per_slot`](#get_previous_epoch_committees_per_slot)
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- [`get_current_epoch_committees_per_slot`](#get_current_epoch_committees_per_slot)
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- [`get_shard_committees_at_slot`](#get_shard_committees_at_slot)
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- [`get_block_root`](#get_block_root)
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- [`get_randao_mix`](#get_randao_mix)
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- [`get_beacon_proposer_index`](#get_beacon_proposer_index)
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- [`merkle_root`](#merkle_root)
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- [`get_attestation_participants`](#get_attestation_participants)
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@ -480,12 +481,12 @@ Unless otherwise indicated, code appearing in `this style` is to be interpreted
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# Randomness and committees
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'latest_randao_mixes': ['hash32'],
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'latest_vdf_outputs': ['hash32'],
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'prev_epoch_start_shard': 'uint64',
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'cur_epoch_start_shard': 'uint64',
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'prev_epoch_calculation_slot': 'uint64',
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'cur_epoch_calculation_slot': 'uint64',
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'prev_epoch_randao_mix': 'hash32',
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'cur_epoch_randao_mix': 'hash32',
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'previous_epoch_start_shard': 'uint64',
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'current_epoch_start_shard': 'uint64',
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'previous_epoch_calculation_slot': 'uint64',
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'current_epoch_calculation_slot': 'uint64',
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'previous_epoch_randao_mix': 'hash32',
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'current_epoch_randao_mix': 'hash32',
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# Custody challenges
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'custody_challenges': [CustodyChallenge],
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@ -891,27 +892,27 @@ def get_shuffling(seed: Hash32,
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**Note**: this definition and the next few definitions make heavy use of repetitive computing. Production implementations are expected to appropriately use caching/memoization to avoid redoing work.
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#### `get_prev_epoch_committees_per_slot`
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#### `get_previous_epoch_committees_per_slot`
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```python
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def get_prev_epoch_committees_per_slot(state: BeaconState) -> int:
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prev_active_validators = get_active_validator_indices(validators, state.prev_epoch_calculation_slot)
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return get_committees_per_slot(len(prev_active_validators))
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def get_previous_epoch_committees_per_slot(state: BeaconState) -> int:
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previous_active_validators = get_active_validator_indices(validators, state.previous_epoch_calculation_slot)
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return get_committees_per_slot(len(previous_active_validators))
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```
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#### `get_cur_epoch_committees_per_slot`
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#### `get_current_epoch_committees_per_slot`
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```python
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def get_cur_epoch_committees_per_slot(state: BeaconState) -> int:
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cur_active_validators = get_active_validator_indices(validators, state.cur_epoch_calculation_slot)
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return get_committees_per_slot(len(cur_active_validators))
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def get_current_epoch_committees_per_slot(state: BeaconState) -> int:
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current_active_validators = get_active_validator_indices(validators, state.current_epoch_calculation_slot)
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return get_committees_per_slot(len(current_active_validators))
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```
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#### `get_shard_committees_at_slot`
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```python
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def get_shard_committees_at_slot(state: BeaconState,
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slot: int) -> Tuple[List[List[int]], int]:
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slot: int) -> List[Tuple[List[int], int]]:
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"""
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Returns (i) the list of committees and (ii) the shard associated with the first committee for the ``slot``.
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"""
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@ -920,22 +921,22 @@ def get_shard_committees_at_slot(state: BeaconState,
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offset = slot % EPOCH_LENGTH
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if slot < earliest_slot + EPOCH_LENGTH:
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committees_per_slot = get_prev_epoch_committees_per_slot(state)
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shuffling = get_shuffling(state.prev_epoch_randao_mix,
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committees_per_slot = get_previous_epoch_committees_per_slot(state)
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shuffling = get_shuffling(state.previous_epoch_randao_mix,
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state.validator_registry,
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state.prev_epoch_calculation_slot)
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start_shard = state.prev_epoch_start_shard
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state.previous_epoch_calculation_slot)
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slot_start_shard = (state.previous_epoch_start_shard + committees_per_slot * offset) % SHARD_COUNT
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else:
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committees_per_slot = get_cur_epoch_committees_per_slot(state)
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shuffling = get_shuffling(state.cur_epoch_randao_mix,
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committees_per_slot = get_current_epoch_committees_per_slot(state)
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shuffling = get_shuffling(state.current_epoch_randao_mix,
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state.validator_registry,
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state.cur_epoch_calculation_slot)
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start_shard = state.cur_epoch_start_shard
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state.current_epoch_calculation_slot)
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slot_start_shard = (state.current_epoch_start_shard + committees_per_slot * offset) % SHARD_COUNT
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return (
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shuffling[committees_per_slot * offset: committees_per_slot * (offset + 1)],
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(start_shard + committees_per_slot * offset) % SHARD_COUNT
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)
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return [
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(shuffling[committees_per_slot * offset + i], (slot_start_shard + i) % SHARD_COUNT)
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for i in range(committees_per_slot)
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]
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```
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**Note**: we plan to replace the shuffling algorithm with a pointwise-evaluable shuffle (see https://github.com/ethereum/eth2.0-specs/issues/323), which will allow calculation of the committees for each slot individually.
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@ -955,6 +956,19 @@ def get_block_root(state: BeaconState,
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`get_block_root(_, s)` should always return `hash_tree_root` of the block in the beacon chain at slot `s`, and `get_shard_committees_at_slot(_, s)` should not change unless the [validator](#dfn-validator) registry changes.
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#### `get_randao_mix`
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```python
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def get_randao_mix(state: BeaconState,
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slot: int) -> Hash32:
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"""
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Returns the randao mix at a recent ``slot``.
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"""
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assert state.slot <= slot + LATEST_RANDAO_MIXES_LENGTH
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assert slot < state.slot
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return state.latest_block_roots[slot % LATEST_RANDAO_MIXES_LENGTH]
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```
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#### `get_beacon_proposer_index`
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```python
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@ -963,8 +977,8 @@ def get_beacon_proposer_index(state: BeaconState,
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"""
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Returns the beacon proposer index for the ``slot``.
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"""
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committees, shard = get_shard_committees_at_slot(state, slot)
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return committees[0][slot % len(committees[0])]
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first_committee, _ = get_shard_committees_at_slot(state, slot)[0]
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return first_committee[slot % len(first_committee)]
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```
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#### `merkle_root`
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@ -990,9 +1004,9 @@ def get_attestation_participants(state: BeaconState,
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Returns the participant indices at for the ``attestation_data`` and ``participation_bitfield``.
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"""
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# Find the relevant committee
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shard_committees, start_shard = get_shard_committees_at_slot(state, attestation_data.slot)
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shard_committee = shard_committee[(attestation_data.shard - start_shard) % SHARD_COUNT]
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# Find the committee in the list with the desired shard
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shard_committees = get_shard_committees_at_slot(state, attestation_data.slot)
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shard_committee = [committee for committee, shard in shard_committees if shard == attestation_data.shard][0]
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assert len(participation_bitfield) == ceil_div8(len(shard_committee))
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# Find the participating attesters in the committee
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@ -1182,12 +1196,12 @@ def get_initial_beacon_state(initial_validator_deposits: List[Deposit],
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# Randomness and committees
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latest_randao_mixes=[ZERO_HASH for _ in range(LATEST_RANDAO_MIXES_LENGTH)],
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latest_vdf_outputs=[ZERO_HASH for _ in range(LATEST_RANDAO_MIXES_LENGTH // EPOCH_LENGTH)],
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prev_epoch_start_shard=0,
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cur_epoch_start_shard=GENESIS_START_SHARD,
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prev_epoch_calculation_slot=GENESIS_SLOT,
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cur_epoch_calculation_slot=GENESIS_SLOT,
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prev_epoch_randao_mix=ZERO_HASH,
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cur_epoch_randao_mix=ZERO_HASH,
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previous_epoch_start_shard=0,
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current_epoch_start_shard=GENESIS_START_SHARD,
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previous_epoch_calculation_slot=GENESIS_SLOT,
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current_epoch_calculation_slot=GENESIS_SLOT,
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previous_epoch_randao_mix=ZERO_HASH,
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current_epoch_randao_mix=ZERO_HASH,
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# Custody challenges
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custody_challenges=[],
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@ -1572,7 +1586,7 @@ All [validators](#dfn-validator):
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**Note**: `previous_epoch_boundary_attesting_balance` balance might be marginally different than `current_epoch_boundary_attesting_balance` during the previous epoch transition. Due to the tight bound on validator churn each epoch and small per-epoch rewards/penalties, the potential balance difference is very low and only marginally affects consensus safety.
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For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `shard_committee_at_slot, start_shard = get_shard_committees_at_slot(slot)`. For every `index in range(len(shard_committee_at_slot))`, let `shard_committee = shard_committee_at_slot[index]`, `shard = (start_shard + index) % SHARD_COUNT`, and compute:
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For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `shard_committee_at_slot = get_shard_committees_at_slot(slot)`. For every `(shard_committee, shard)` in `shard_committee_at_slot`, compute:
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* Let `shard_block_root` be `state.latest_crosslinks[shard].shard_block_root`
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* Let `attesting_validator_indices(shard_committee, shard_block_root)` be the union of the [validator](#dfn-validator) index sets given by `[get_attestation_participants(state, a.data, a.participation_bitfield) for a in current_epoch_attestations + previous_epoch_attestations if a.shard == shard and a.shard_block_root == shard_block_root]`.
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@ -1605,7 +1619,7 @@ Set `state.finalized_slot = state.previous_justified_slot` if any of the followi
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### Crosslinks
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For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `shard_committee_at_slot, start_shard = get_shard_committees_at_slot(slot)`. For every `index in range(len(shard_committee_at_slot))`, let `shard_committee = shard_committee_at_slot[index]`, `shard = (start_shard + index) % SHARD_COUNT`, and compute:
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For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `shard_committee_at_slot = get_shard_committees_at_slot(slot)`. For every `(shard_committee, shard)` in `shard_committee_at_slot`, compute:
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* Set `state.latest_crosslinks[shard] = CrosslinkRecord(slot=state.slot, shard_block_root=winning_root(shard_committee))` if `3 * total_attesting_balance(shard_committee) >= 2 * total_balance(shard_committee)`.
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@ -1676,7 +1690,7 @@ def process_ejections(state: BeaconState) -> None:
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If the following are satisfied:
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* `state.finalized_slot > state.validator_registry_latest_change_slot`
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* `state.latest_crosslinks[shard].slot > state.validator_registry_latest_change_slot` for every shard number `shard` in `[(state.cur_epoch_start_shard + i) % SHARD_COUNT for i in range(get_cur_epoch_committees_per_slot(state) * EPOCH_LENGTH)]` (that is, for every shard in the current committees)
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* `state.latest_crosslinks[shard].slot > state.validator_registry_latest_change_slot` for every shard number `shard` in `[(state.current_epoch_start_shard + i) % SHARD_COUNT for i in range(get_current_epoch_committees_per_slot(state) * EPOCH_LENGTH)]` (that is, for every shard in the current committees)
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update the validator registry and associated fields by running
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@ -1726,19 +1740,19 @@ def update_validator_registry(state: BeaconState) -> None:
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and perform the following updates:
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* Set `state.prev_epoch_calculation_slot = state.cur_epoch_calculation_slot`
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* Set `state.prev_epoch_start_shard = state.cur_epoch_start_shard`
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* Set `state.prev_epoch_randao_mix = state.cur_epoch_randao_mix`
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* Set `state.cur_epoch_calculation_slot = state.slot`
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* Set `state.cur_epoch_start_shard = (state.cur_epoch_start_shard + get_cur_epoch_committees_per_slot(state) * EPOCH_LENGTH) % SHARD_COUNT`
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* Set `state.cur_epoch_randao_mix = state.latest_randao_mixes[(state.cur_epoch_calculation_slot - SEED_LOOKAHEAD) % LATEST_RANDAO_MIXES_LENGTH]`
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* Set `state.previous_epoch_calculation_slot = state.current_epoch_calculation_slot`
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* Set `state.previous_epoch_start_shard = state.current_epoch_start_shard`
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* Set `state.previous_epoch_randao_mix = state.current_epoch_randao_mix`
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* Set `state.current_epoch_calculation_slot = state.slot`
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* Set `state.current_epoch_start_shard = (state.current_epoch_start_shard + get_current_epoch_committees_per_slot(state) * EPOCH_LENGTH) % SHARD_COUNT`
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* Set `state.current_epoch_randao_mix = get_randao_mix(state, state.current_epoch_calculation_slot - SEED_LOOKAHEAD)`
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If a validator registry update does _not_ happen do the following:
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* Set `state.prev_epoch_calculation_slot = state.cur_epoch_calculation_slot`
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* Set `state.prev_epoch_start_shard = state.cur_epoch_start_shard`
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* Set `state.previous_epoch_calculation_slot = state.current_epoch_calculation_slot`
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* Set `state.previous_epoch_start_shard = state.current_epoch_start_shard`
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* Let `epochs_since_last_registry_change = (state.slot - state.validator_registry_latest_change_slot) // EPOCH_LENGTH`.
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* If `epochs_since_last_registry_change` is an exact power of 2, set `state.cur_epoch_calculation_slot = state.slot` and `state.cur_epoch_randao_mix = state.latest_randao_mixes[(state.cur_epoch_calculation_slot - SEED_LOOKAHEAD) % LATEST_RANDAO_MIXES_LENGTH]`. Note that `state.cur_epoch_start_shard` is left unchanged.
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* If `epochs_since_last_registry_change` is an exact power of 2, set `state.current_epoch_calculation_slot = state.slot` and `state.current_epoch_randao_mix = state.latest_randao_mixes[(state.current_epoch_calculation_slot - SEED_LOOKAHEAD) % LATEST_RANDAO_MIXES_LENGTH]`. Note that `state.current_epoch_start_shard` is left unchanged.
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Regardless of whether or not a validator set change happens, run the following:
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