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Merge pull request #495 from ethereum/vbuterin-patch-3 

A few more state.slot -> current/previous/next epoch start slot changes
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Danny Ryan 2019-01-23 21:12:23 -06:00 committed by GitHub
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specs/core/0_beacon-chain.md
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@ -1575,12 +1575,13 @@ The steps below happen when `state.slot % EPOCH_LENGTH == EPOCH_LENGTH - 1`.
### Helpers
* Let `next_epoch_start_slot = state.slot + 1`.
* Let `current_epoch_start_slot = state.slot - (EPOCH_LENGTH + 1)`.
* Let `previous_epoch_start_slot = state.slot - 2 * EPOCH_LENGTH + 1` if `state.slot > EPOCH_LENGTH` else `current_epoch_start_slot`.
All [validators](#dfn-validator):
* Let `active_validator_indices = get_active_validator_indices(state.validator_registry, state.slot)`.
* Let `active_validator_indices = get_active_validator_indices(state.validator_registry, current_epoch_start_slot)`.
* Let `total_balance = sum([get_effective_balance(state, i) for i in active_validator_indices])`.
[Validators](#dfn-Validator) attesting during the current epoch:
@ -1611,7 +1612,7 @@ All [validators](#dfn-validator):
**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.
For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
For every `slot in range(previous_epoch_start_slot, next_epoch_start_slot)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
* Let `shard_block_root` be `state.latest_crosslinks[shard].shard_block_root`
* Let `attesting_validator_indices(crosslink_committee, shard_block_root)` be the union of the [validator](#dfn-validator) index sets given by `[get_attestation_participants(state, a.data, a.aggregation_bitfield) for a in current_epoch_attestations + previous_epoch_attestations if a.data.shard == shard and a.data.shard_block_root == shard_block_root]`.
@ -1655,9 +1656,9 @@ Finally, update the following:
### Crosslinks
For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
For every `slot in range(previous_epoch_start_slot, next_epoch_start_slot)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
* Set `state.latest_crosslinks[shard] = Crosslink(slot=state.slot, shard_block_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * total_balance(crosslink_committee)`.
* Set `state.latest_crosslinks[shard] = Crosslink(slot=current_epoch_start_slot, shard_block_root=winning_root(crosslink_committee))` if `3 * total_attesting_balance(crosslink_committee) >= 2 * total_balance(crosslink_committee)`.
### Rewards and penalties
@ -1671,7 +1672,7 @@ First, we define some additional helpers:
Note: When applying penalties in the following balance recalculations implementers should make sure the `uint64` does not underflow.
* Let `epochs_since_finality = (state.slot - state.finalized_slot) // EPOCH_LENGTH`.
* Let `epochs_since_finality = (next_epoch_start_slot - state.finalized_slot) // EPOCH_LENGTH`.
Case 1: `epochs_since_finality <= 4`:
@ -1692,7 +1693,7 @@ Case 2: `epochs_since_finality > 4`:
* Any [active validator](#dfn-active-validator) `index` not in `previous_epoch_justified_attester_indices`, loses `inactivity_penalty(state, index, epochs_since_finality)`.
* Any [active validator](#dfn-active-validator) `index` not in `previous_epoch_boundary_attester_indices`, loses `inactivity_penalty(state, index, epochs_since_finality)`.
* Any [active validator](#dfn-active-validator) `index` not in `previous_epoch_head_attester_indices`, loses `base_reward(state, index)`.
* Any [active_validator](#dfn-active-validator) `index` with `validator.penalized_slot <= state.slot`, loses `2 * inactivity_penalty(state, index, epochs_since_finality) + base_reward(state, index)`.
* Any [active_validator](#dfn-active-validator) `index` with `validator.penalized_slot <= current_epoch_start_slot`, loses `2 * inactivity_penalty(state, index, epochs_since_finality) + base_reward(state, index)`.
* Any [validator](#dfn-validator) `index` in `previous_epoch_attester_indices` loses `base_reward(state, index) - base_reward(state, index) * MIN_ATTESTATION_INCLUSION_DELAY // inclusion_distance(state, index)`
#### Attestation inclusion
@ -1701,7 +1702,7 @@ For each `index` in `previous_epoch_attester_indices`, we determine the proposer
#### Crosslinks
For every `slot in range(state.slot - 2 * EPOCH_LENGTH, state.slot - EPOCH_LENGTH)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
For every `slot in range(previous_epoch_start_slot, current_epoch_start_slot)`, let `crosslink_committees_at_slot = get_crosslink_committees_at_slot(state, slot)`. For every `(crosslink_committee, shard)` in `crosslink_committees_at_slot`, compute:
* If `index in attesting_validators(crosslink_committee)`, `state.validator_balances[index] += base_reward(state, index) * total_attesting_balance(crosslink_committee) // total_balance(crosslink_committee))`.
* If `index not in attesting_validators(crosslink_committee)`, `state.validator_balances[index] -= base_reward(state, index)`.
@ -1716,7 +1717,7 @@ def process_ejections(state: BeaconState) -> None:
Iterate through the validator registry
and eject active validators with balance below ``EJECTION_BALANCE``.
"""
for index in get_active_validator_indices(state.validator_registry, state.slot):
for index in get_active_validator_indices(state.validator_registry, current_epoch_start_slot):
if state.validator_balances[index] < EJECTION_BALANCE:
exit_validator(state, index)
```
@ -1743,7 +1744,7 @@ def update_validator_registry(state: BeaconState) -> None:
Note that this function mutates ``state``.
"""
# The active validators
active_validator_indices = get_active_validator_indices(state.validator_registry, state.slot)
active_validator_indices = get_active_validator_indices(state.validator_registry, current_epoch_start_slot)
# The total effective balance of active validators
total_balance = sum([get_effective_balance(state, i) for i in active_validator_indices])