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EIP-7251: Fix off-by-one in churn computations #3682

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Merged
ralexstokes merged 1 commit into from
Apr 17, 2024
Merged

EIP-7251: Fix off-by-one in churn computations #3682

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53 changes: 29 additions & 24 deletions specs/electra/beacon-chain.md
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Original file line number Diff line number Diff line change
Expand Up @@ -657,22 +657,24 @@ def queue_entire_balance_and_reset_validator(state: BeaconState, index: Validato

```python
def compute_exit_epoch_and_update_churn(state: BeaconState, exit_balance: Gwei) -> Epoch:
earliest_exit_epoch = compute_activation_exit_epoch(get_current_epoch(state))
earliest_exit_epoch = max(state.earliest_exit_epoch, compute_activation_exit_epoch(get_current_epoch(state)))
per_epoch_churn = get_activation_exit_churn_limit(state)
# New epoch for exits.
if state.earliest_exit_epoch < earliest_exit_epoch:
state.earliest_exit_epoch = earliest_exit_epoch
state.exit_balance_to_consume = per_epoch_churn

if exit_balance <= state.exit_balance_to_consume:
# Exit fits in the current earliest epoch.
state.exit_balance_to_consume -= exit_balance
exit_balance_to_consume = per_epoch_churn
else:
# Exit doesn't fit in the current earliest epoch.
balance_to_process = exit_balance - state.exit_balance_to_consume
additional_epochs, remainder = divmod(balance_to_process, per_epoch_churn)
state.earliest_exit_epoch += additional_epochs + 1
state.exit_balance_to_consume = per_epoch_churn - remainder
exit_balance_to_consume = state.exit_balance_to_consume

# Exit doesn't fit in the current earliest epoch.
if exit_balance > exit_balance_to_consume:
balance_to_process = exit_balance - exit_balance_to_consume
additional_epochs = (balance_to_process - 1) // per_epoch_churn + 1
earliest_exit_epoch += additional_epochs
exit_balance_to_consume += additional_epochs * per_epoch_churn

# Consume the balance and update state variables.
state.exit_balance_to_consume = exit_balance_to_consume - exit_balance
state.earliest_exit_epoch = earliest_exit_epoch

return state.earliest_exit_epoch
```
Expand All @@ -681,22 +683,25 @@ def compute_exit_epoch_and_update_churn(state: BeaconState, exit_balance: Gwei)

```python
def compute_consolidation_epoch_and_update_churn(state: BeaconState, consolidation_balance: Gwei) -> Epoch:
earliest_consolidation_epoch = compute_activation_exit_epoch(get_current_epoch(state))
earliest_consolidation_epoch = max(
state.earliest_consolidation_epoch, compute_activation_exit_epoch(get_current_epoch(state)))
per_epoch_consolidation_churn = get_consolidation_churn_limit(state)
# New epoch for consolidations.
if state.earliest_consolidation_epoch < earliest_consolidation_epoch:
state.earliest_consolidation_epoch = earliest_consolidation_epoch
state.consolidation_balance_to_consume = per_epoch_consolidation_churn

if consolidation_balance <= state.consolidation_balance_to_consume:
# Consolidation fits in the current earliest consolidation epoch.
state.consolidation_balance_to_consume -= consolidation_balance
consolidation_balance_to_consume = per_epoch_consolidation_churn
else:
# Consolidation doesn't fit in the current earliest epoch.
balance_to_process = consolidation_balance - state.consolidation_balance_to_consume
additional_epochs, remainder = divmod(balance_to_process, per_epoch_consolidation_churn)
state.earliest_consolidation_epoch += additional_epochs + 1
state.consolidation_balance_to_consume = per_epoch_consolidation_churn - remainder
consolidation_balance_to_consume = state.consolidation_balance_to_consume

# Consolidation doesn't fit in the current earliest epoch.
if consolidation_balance > consolidation_balance_to_consume:
balance_to_process = consolidation_balance - consolidation_balance_to_consume
additional_epochs = (balance_to_process - 1) // per_epoch_consolidation_churn + 1
earliest_consolidation_epoch += additional_epochs
consolidation_balance_to_consume += additional_epochs * per_epoch_consolidation_churn

# Consume the balance and update state variables.
state.consolidation_balance_to_consume = consolidation_balance_to_consume - consolidation_balance
state.earliest_consolidation_epoch = earliest_consolidation_epoch

return state.earliest_consolidation_epoch
```
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