Avoid unnecessary clamp on previous_epoch by genesis_epoch

eth2/beacon/committee_helpers.py

@@ -289,13 +289,12 @@ def get_crosslink_committees_at_slot(
     """
     Return the list of ``(committee, shard)`` tuples for the ``slot``.
     """
-    genesis_epoch = committee_config.GENESIS_EPOCH
     shard_count = committee_config.SHARD_COUNT
     slots_per_epoch = committee_config.SLOTS_PER_EPOCH
 
     epoch = slot_to_epoch(slot, slots_per_epoch)
     current_epoch = state.current_epoch(slots_per_epoch)
-    previous_epoch = state.previous_epoch(slots_per_epoch, genesis_epoch)
+    previous_epoch = state.previous_epoch(slots_per_epoch)
     next_epoch = state.next_epoch(slots_per_epoch)
 
     validate_epoch_within_previous_and_next(epoch, previous_epoch, next_epoch)
@@ -358,12 +357,8 @@ def get_beacon_proposer_index(state: 'BeaconState',
     Return the beacon proposer index for the ``slot``.
     """
     epoch = slot_to_epoch(slot, committee_config.SLOTS_PER_EPOCH)
-    current_epoch = state.current_epoch(committee_config.SLOTS_PER_EPOCH)
-    previous_epoch = state.previous_epoch(
-        committee_config.SLOTS_PER_EPOCH,
-        committee_config.GENESIS_EPOCH,
-    )
-    next_epoch = Epoch(current_epoch + 1)
+    previous_epoch = state.previous_epoch(committee_config.SLOTS_PER_EPOCH)
+    next_epoch = state.next_epoch(committee_config.SLOTS_PER_EPOCH)
 
     validate_epoch_within_previous_and_next(epoch, previous_epoch, next_epoch)
 

eth2/beacon/epoch_processing_helpers.py

@@ -56,12 +56,11 @@
 def get_previous_epoch_boundary_attestations(
         state: 'BeaconState',
         slots_per_epoch: int,
-        genesis_epoch: Epoch,
         latest_block_roots_length: int) -> Iterable[PendingAttestationRecord]:
     beacon_block_root = get_block_root(
         state,
         get_epoch_start_slot(
-            state.previous_epoch(slots_per_epoch, genesis_epoch),
+            state.previous_epoch(slots_per_epoch),
             slots_per_epoch,
         ),
         latest_block_roots_length,
@@ -75,7 +74,6 @@ def get_previous_epoch_boundary_attestations(
 def get_previous_epoch_matching_head_attestations(
         state: 'BeaconState',
         slots_per_epoch: int,
-        genesis_epoch: Epoch,
         latest_block_roots_length: int) -> Iterable[PendingAttestationRecord]:
     for attestation in state.previous_epoch_attestations:
         beacon_block_root = get_block_root(
@@ -162,12 +160,79 @@ def get_epoch_boundary_attester_indices(
             )
 
 
+@to_tuple
+def get_attesting_indices(state: 'BeaconState',
+                          attestations: Sequence[PendingAttestationRecord],
+                          config: CommitteeConfig) -> Iterable[ValidatorIndex]:
+    output: Set[ValidatorIndex] = set()
+    for a in attestations:
+        participants = get_attestation_participants(state, a.data, a.aggregation_bitfield, config)
+        output = output.union(participants)
+    for result in sorted(output):
+        yield result
+
+
+def get_attesting_balance(state: 'BeaconState',
+                          attestations: Sequence[PendingAttestationRecord],
+                          config: 'BeaconConfig') -> Gwei:
+    return get_total_balance(
+        state.validator_balances,
+        get_attesting_indices(state, attestations, CommitteeConfig(config)),
+        config.MAX_DEPOSIT_AMOUNT,
+    )
+
+
+@to_tuple
+def _get_boundary_attestations_in_epoch(
+        *,
+        state: 'BeaconState',
+        attestations: Sequence[PendingAttestationRecord],
+        epoch: Epoch,
+        config: 'BeaconConfig') -> Iterable[PendingAttestationRecord]:
+    slot = get_epoch_start_slot(epoch, config.SLOTS_PER_EPOCH)
+    for a in attestations:
+        block_root = get_block_root(
+            state,
+            slot,
+            config.LATEST_BLOCK_ROOTS_LENGTH
+        )
+        if a.data.epoch_boundary_root == block_root:
+            yield a
+
+
+def _get_current_epoch_boundary_attestations(
+        state: 'BeaconState',
+        config: 'BeaconConfig') -> Tuple[PendingAttestationRecord]:
+    current_epoch = state.current_epoch(config.SLOTS_PER_EPOCH)
+    current_epoch_attestations = state.current_epoch_attestations
+
+    return _get_boundary_attestations_in_epoch(
+        state=state,
+        attestations=current_epoch_attestations,
+        epoch=current_epoch,
+        config=config,
+    )
+
+
+def _get_previous_epoch_boundary_attestations(
+        state: 'BeaconState',
+        config: 'BeaconConfig') -> Tuple[PendingAttestationRecord]:
+    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH)
+    previous_epoch_attestations = state.previous_epoch_attestations
+
+    return _get_boundary_attestations_in_epoch(
+        state=state,
+        attestations=previous_epoch_attestations,
+        epoch=previous_epoch,
+        config=config,
+    )
+
+
 def get_epoch_boundary_attesting_balances(
         current_epoch: Epoch,
         previous_epoch: Epoch,
         state: 'BeaconState',
         config: 'BeaconConfig') -> Tuple[Gwei, Gwei]:
-
     previous_epoch_boundary_root = get_block_root(
         state,
         get_epoch_start_slot(previous_epoch, config.SLOTS_PER_EPOCH),

eth2/beacon/state_machines/forks/serenity/epoch_processing.py

@@ -210,7 +210,7 @@ def _get_finalized_epoch(
 def process_justification(state: BeaconState, config: BeaconConfig) -> BeaconState:
 
     current_epoch = state.current_epoch(config.SLOTS_PER_EPOCH)
-    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH)
+    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH)
 
     current_epoch_justifiable, previous_epoch_justifiable = _current_previous_epochs_justifiable(
         state,
@@ -275,7 +275,7 @@ def process_crosslinks(state: BeaconState, config: BeaconConfig) -> BeaconState:
         for index in range(len(state.validator_registry))
     }
     previous_epoch_start_slot = get_epoch_start_slot(
-        state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH),
+        state.previous_epoch(config.SLOTS_PER_EPOCH),
         config.SLOTS_PER_EPOCH,
     )
     next_epoch_start_slot = get_epoch_start_slot(
@@ -523,7 +523,6 @@ def _process_rewards_and_penalties_for_finality(
     previous_epoch_boundary_attestations = get_previous_epoch_boundary_attestations(
         state,
         config.SLOTS_PER_EPOCH,
-        config.GENESIS_EPOCH,
         config.LATEST_BLOCK_ROOTS_LENGTH,
     )
     previous_epoch_boundary_attester_indices = get_attester_indices_from_attestations(
@@ -535,7 +534,6 @@ def _process_rewards_and_penalties_for_finality(
     previous_epoch_head_attestations = get_previous_epoch_matching_head_attestations(
         state,
         config.SLOTS_PER_EPOCH,
-        config.GENESIS_EPOCH,
         config.LATEST_BLOCK_ROOTS_LENGTH,
     )
     previous_epoch_head_attester_indices = get_attester_indices_from_attestations(
@@ -582,7 +580,7 @@ def _process_rewards_and_penalties_for_crosslinks(
         effective_balances: Dict[ValidatorIndex, Gwei],
         base_rewards: Dict[ValidatorIndex, Gwei]) -> Tuple[Dict[ValidatorIndex, Gwei], Dict[ValidatorIndex, Gwei]]:  # noqa: E501
     previous_epoch_start_slot = get_epoch_start_slot(
-        state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH),
+        state.previous_epoch(config.SLOTS_PER_EPOCH),
         config.SLOTS_PER_EPOCH,
     )
     current_epoch_start_slot = get_epoch_start_slot(
@@ -637,9 +635,14 @@ def process_rewards_and_penalties(state: BeaconState, config: BeaconConfig) -> B
     previous_epoch_active_validator_indices = set(
         get_active_validator_indices(
             state.validator_registry,
-            state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH)
+            state.previous_epoch(config.SLOTS_PER_EPOCH)
         )
     )
+
+    # do not proceed if there are no validators in the previous epoch
+    if not previous_epoch_active_validator_indices:
+        return state
+
     previous_total_balance: Gwei = get_total_balance(
         state.validator_balances,
         tuple(previous_epoch_active_validator_indices),

eth2/beacon/state_machines/forks/serenity/operation_processing.py

@@ -139,7 +139,7 @@ def process_attestations(state: BeaconState,
         )
 
     # update attestations
-    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH)
+    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH)
     current_epoch = state.current_epoch(config.SLOTS_PER_EPOCH)
     new_previous_epoch_pending_attestations = []
     new_current_epoch_pending_attestations = []

eth2/beacon/tools/builder/validator.py

@@ -635,9 +635,8 @@ def get_committee_assignment(
     ``CommitteeAssignment.is_proposer`` is a bool signalling if the validator is expected to
         propose a beacon block at the assigned slot.
     """
-    current_epoch = state.current_epoch(config.SLOTS_PER_EPOCH)
-    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH)
-    next_epoch = Epoch(current_epoch + 1)
+    previous_epoch = state.previous_epoch(config.SLOTS_PER_EPOCH)
+    next_epoch = state.next_epoch(config.SLOTS_PER_EPOCH)
 
     validate_epoch_within_previous_and_next(epoch, previous_epoch, next_epoch)
 

eth2/beacon/types/states.py

@@ -303,8 +303,8 @@ def update_validator(self,
     def current_epoch(self, slots_per_epoch: int) -> Epoch:
         return slot_to_epoch(self.slot, slots_per_epoch)
 
-    def previous_epoch(self, slots_per_epoch: int, genesis_epoch: int) -> Epoch:
-        return Epoch(max(self.current_epoch(slots_per_epoch) - 1, genesis_epoch))
+    def previous_epoch(self, slots_per_epoch: int) -> Epoch:
+        return Epoch(self.current_epoch(slots_per_epoch) - 1)
 
     def next_epoch(self, slots_per_epoch: int) -> Epoch:
         return Epoch(self.current_epoch(slots_per_epoch) + 1)

tests/eth2/beacon/state_machines/forks/test_serenity_epoch_processing.py

@@ -740,7 +740,7 @@ def mock_get_beacon_proposer_index(state,
     }
 
     prev_epoch_start_slot = get_epoch_start_slot(
-        state.previous_epoch(config.SLOTS_PER_EPOCH, config.GENESIS_EPOCH), slots_per_epoch,
+        state.previous_epoch(config.SLOTS_PER_EPOCH), slots_per_epoch,
     )
     prev_epoch_crosslink_committees = [
         get_crosslink_committees_at_slot(

tests/eth2/beacon/state_machines/test_state_transition.py

@@ -16,7 +16,8 @@
         'genesis_slot,'
     ),
     [
-        (0),
+        # start high enough so that we do not end up with negative numbers
+        (104),
     ]
 )
 @pytest.mark.parametrize(
@@ -54,6 +55,8 @@ def test_per_slot_transition(base_db,
                              config,
                              state_slot,
                              keymap):
+    state_slot += config.GENESIS_SLOT
+
     chaindb = BeaconChainDB(base_db)
     chaindb.persist_block(genesis_block, SerenityBeaconBlock)
     chaindb.persist_state(genesis_state)

tests/eth2/beacon/test_committee_helpers.py

@@ -326,10 +326,9 @@ def mock_get_epoch_committee_count(
 @pytest.mark.parametrize(
     (
         'genesis_slot,'
-        'genesis_epoch,'
     ),
     [
-        (0, 0),
+        0,
     ],
 )
 @pytest.mark.parametrize(
@@ -387,7 +386,6 @@ def test_get_crosslink_committees_at_slot(
         slots_per_epoch,
         target_committee_size,
         shard_count,
-        genesis_epoch,
         committee_config,
         registry_change,
         should_reseed,
@@ -473,8 +471,8 @@ def mock_generate_seed(state,
     #
     epoch = slot_to_epoch(slot, slots_per_epoch)
     current_epoch = state.current_epoch(slots_per_epoch)
-    previous_epoch = state.previous_epoch(slots_per_epoch, genesis_epoch)
-    next_epoch = current_epoch + 1
+    previous_epoch = state.previous_epoch(slots_per_epoch)
+    next_epoch = state.next_epoch(slots_per_epoch)
 
     if epoch == current_epoch:
         seed = state.current_shuffling_seed
@@ -507,10 +505,9 @@ def mock_generate_seed(state,
 @pytest.mark.parametrize(
     (
         'genesis_slot,'
-        'genesis_epoch,'
     ),
     [
-        (0, 0),
+        0,
     ],
 )
 @pytest.mark.parametrize(
@@ -547,7 +544,6 @@ def test_get_beacon_proposer_index(
         registry_change,
         success,
         sample_state,
-        genesis_epoch,
         target_committee_size,
         shard_count,
         committee_config):
@@ -632,7 +628,6 @@ def test_get_attestation_participants(
         aggregation_bitfield,
         expected,
         sample_state,
-        genesis_epoch,
         target_committee_size,
         shard_count,
         committee_config,