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Update inactivity penalty deltas processing 

Two main changes:

1. Inactivity scores are modified to decrease slowly for inactive validators when we are not in a leak, and quickly for active validators
2. The inactivity penalties are applied even not during a leak (note that inactivity _scores_ decrease when outside of a leak)

This has the effect that the inactivity leak "overshoots" the target of finalizing again, and keeps leaking balances a bit more. For inactive validators, this PR sets post-leak recovery to happen 3x faster than the during-leak increase, so if a validator loses 3% during a leak, if they stay offline they should expect to lose another 1% until their score decreases back to zero.
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vbuterin 2021-05-07 11:05:27 -07:00 committed by GitHub
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1 changed files with 17 additions and 14 deletions
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specs/altair/beacon-chain.md
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@ -120,6 +120,7 @@ This patch updates a few configuration values to move penalty parameters closer
| - | - | | - | - |
| `SYNC_COMMITTEE_SIZE` | `uint64(2**9)` (= 512) | | `SYNC_COMMITTEE_SIZE` | `uint64(2**9)` (= 512) |
| `INACTIVITY_SCORE_BIAS` | `uint64(4)` | | `INACTIVITY_SCORE_BIAS` | `uint64(4)` |
| `INACTIVITY_SCORE_RECOVERY_RATE` | `uint64(16)` |
### Time parameters ### Time parameters
@ -397,17 +398,16 @@ def get_inactivity_penalty_deltas(state: BeaconState) -> Tuple[Sequence[Gwei], S
""" """
rewards = [Gwei(0) for _ in range(len(state.validators))] rewards = [Gwei(0) for _ in range(len(state.validators))]
penalties = [Gwei(0) for _ in range(len(state.validators))] penalties = [Gwei(0) for _ in range(len(state.validators))]
if is_in_inactivity_leak(state): previous_epoch = get_previous_epoch(state)
previous_epoch = get_previous_epoch(state) matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch)
matching_target_indices = get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, previous_epoch) for index in get_eligible_validator_indices(state):
for index in get_eligible_validator_indices(state): for (_, weight) in get_flag_indices_and_weights():
for (_, weight) in get_flag_indices_and_weights(): # This inactivity penalty cancels the flag reward corresponding to the flag index
# This inactivity penalty cancels the flag reward corresponding to the flag index penalties[index] += Gwei(get_base_reward(state, index) * weight // WEIGHT_DENOMINATOR)
penalties[index] += Gwei(get_base_reward(state, index) * weight // WEIGHT_DENOMINATOR) if index not in matching_target_indices:
if index not in matching_target_indices: penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index]
penalty_numerator = state.validators[index].effective_balance * state.inactivity_scores[index] penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR
penalty_denominator = INACTIVITY_SCORE_BIAS * INACTIVITY_PENALTY_QUOTIENT_ALTAIR penalties[index] += Gwei(penalty_numerator // penalty_denominator)
penalties[index] += Gwei(penalty_numerator // penalty_denominator)
return rewards, penalties return rewards, penalties
``` ```
@ -621,11 +621,14 @@ def process_justification_and_finalization(state: BeaconState) -> None:
```python ```python
def process_inactivity_updates(state: BeaconState) -> None: def process_inactivity_updates(state: BeaconState) -> None:
for index in get_eligible_validator_indices(state): for index in get_eligible_validator_indices(state):
# Increase inactivity score of inactive validators
if index in get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)): if index in get_unslashed_participating_indices(state, TIMELY_TARGET_FLAG_INDEX, get_previous_epoch(state)):
if state.inactivity_scores[index] > 0: state.inactivity_scores[index] -= min(1, state.inactivity_scores[index])
state.inactivity_scores[index] -= 1 else:
elif is_in_inactivity_leak(state):
state.inactivity_scores[index] += INACTIVITY_SCORE_BIAS state.inactivity_scores[index] += INACTIVITY_SCORE_BIAS
# Decrease the score of all validators for forgiveness when not during a leak
if not if is_in_inactivity_leak(state):
state.inactivity_scores[index] -= min(INACTIVITY_SCORE_RECOVERY_RATE, state.inactivity_scores[index])
``` ```
#### Rewards and penalties #### Rewards and penalties