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Add `compute_sync_committee_period_at_slot`

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Etan Kissling 2022-07-08 21:59:09 -07:00
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1 changed files with 17 additions and 9 deletions
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specs/altair/sync-protocol.md
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@ -21,6 +21,7 @@
- [`is_better_update`](#is_better_update) - [`is_better_update`](#is_better_update)
- [`get_safety_threshold`](#get_safety_threshold) - [`get_safety_threshold`](#get_safety_threshold)
- [`get_subtree_index`](#get_subtree_index) - [`get_subtree_index`](#get_subtree_index)
- [`compute_sync_committee_period_at_slot`](#compute_sync_committee_period_at_slot)
- [Light client state updates](#light-client-state-updates) - [Light client state updates](#light-client-state-updates)
- [`process_slot_for_light_client_store`](#process_slot_for_light_client_store) - [`process_slot_for_light_client_store`](#process_slot_for_light_client_store)
- [`validate_light_client_update`](#validate_light_client_update) - [`validate_light_client_update`](#validate_light_client_update)
@ -135,12 +136,12 @@ def is_better_update(new_update: LightClientUpdate, old_update: LightClientUpdat
# Compare sync committee finality # Compare sync committee finality
if new_has_finality: if new_has_finality:
new_has_sync_committee_finality = ( new_has_sync_committee_finality = (
compute_sync_committee_period(compute_epoch_at_slot(new_update.finalized_header.slot)) == compute_sync_committee_period_at_slot(new_update.finalized_header.slot) ==
compute_sync_committee_period(compute_epoch_at_slot(new_update.attested_header.slot)) compute_sync_committee_period_at_slot(new_update.attested_header.slot)
) )
old_has_sync_committee_finality = ( old_has_sync_committee_finality = (
compute_sync_committee_period(compute_epoch_at_slot(old_update.finalized_header.slot)) == compute_sync_committee_period_at_slot(old_update.finalized_header.slot) ==
compute_sync_committee_period(compute_epoch_at_slot(old_update.attested_header.slot)) compute_sync_committee_period_at_slot(old_update.attested_header.slot)
) )
if new_has_sync_committee_finality != old_has_sync_committee_finality: if new_has_sync_committee_finality != old_has_sync_committee_finality:
return new_has_sync_committee_finality > old_has_sync_committee_finality return new_has_sync_committee_finality > old_has_sync_committee_finality
@ -172,6 +173,13 @@ def get_subtree_index(generalized_index: GeneralizedIndex) -> uint64:
return uint64(generalized_index % 2**(floorlog2(generalized_index))) return uint64(generalized_index % 2**(floorlog2(generalized_index)))
``` ```
### `compute_sync_committee_period_at_slot`
```python
def compute_sync_committee_period_at_slot(slot: Slot) -> uint64:
return compute_sync_committee_period(compute_epoch_at_slot(slot))
```
## Light client state updates ## Light client state updates
A light client maintains its state in a `store` object of type `LightClientStore` and receives `update` objects of type `LightClientUpdate`. Every `update` triggers `process_light_client_update(store, update, current_slot, genesis_validators_root)` where `current_slot` is the current slot based on a local clock. `process_slot_for_light_client_store` is triggered every time the current slot increments. A light client maintains its state in a `store` object of type `LightClientStore` and receives `update` objects of type `LightClientUpdate`. Every `update` triggers `process_light_client_update(store, update, current_slot, genesis_validators_root)` where `current_slot` is the current slot based on a local clock. `process_slot_for_light_client_store` is triggered every time the current slot increments.
@ -207,12 +215,12 @@ def validate_light_client_update(store: LightClientStore,
# Verify update does not skip a sync committee period # Verify update does not skip a sync committee period
assert current_slot >= update.signature_slot > update.attested_header.slot >= update.finalized_header.slot assert current_slot >= update.signature_slot > update.attested_header.slot >= update.finalized_header.slot
store_period = compute_sync_committee_period(compute_epoch_at_slot(store.finalized_header.slot)) store_period = compute_sync_committee_period_at_slot(store.finalized_header.slot)
signature_period = compute_sync_committee_period(compute_epoch_at_slot(update.signature_slot)) signature_period = compute_sync_committee_period_at_slot(update.signature_slot)
assert signature_period in (store_period, store_period + 1) assert signature_period in (store_period, store_period + 1)
# Verify update is relevant # Verify update is relevant
attested_period = compute_sync_committee_period(compute_epoch_at_slot(update.attested_header.slot)) attested_period = compute_sync_committee_period_at_slot(update.attested_header.slot)
assert update.attested_header.slot > store.finalized_header.slot assert update.attested_header.slot > store.finalized_header.slot
# Verify that the `finality_branch`, if present, confirms `finalized_header` # Verify that the `finality_branch`, if present, confirms `finalized_header`
@ -269,8 +277,8 @@ def validate_light_client_update(store: LightClientStore,
```python ```python
def apply_light_client_update(store: LightClientStore, update: LightClientUpdate) -> None: def apply_light_client_update(store: LightClientStore, update: LightClientUpdate) -> None:
store_period = compute_sync_committee_period(compute_epoch_at_slot(store.finalized_header.slot)) store_period = compute_sync_committee_period_at_slot(store.finalized_header.slot)
finalized_period = compute_sync_committee_period(compute_epoch_at_slot(update.finalized_header.slot)) finalized_period = compute_sync_committee_period_at_slot(update.finalized_header.slot)
if finalized_period == store_period + 1: if finalized_period == store_period + 1:
store.current_sync_committee = store.next_sync_committee store.current_sync_committee = store.next_sync_committee
store.next_sync_committee = update.next_sync_committee store.next_sync_committee = update.next_sync_committee