Sync with spec, update get_block_root and get_shard_committees_at_slot

Author: hwwhww

eth/beacon/helpers.py

@@ -1,5 +1,4 @@
 from typing import (
-    Any,
     Iterable,
     Sequence,
     Tuple,
@@ -63,47 +62,43 @@
     from eth.beacon.types.validator_records import ValidatorRecord  # noqa: F401
 
 
-def _get_element_from_recent_list(
-        target_list: Sequence[Any],
-        target_slot: SlotNumber,
-        slot_relative_position: SlotNumber) -> Any:
+#
+# Get block root
+#
+def _get_block_root(
+        latest_block_roots: Sequence[Hash32],
+        state_slot: SlotNumber,
+        slot: SlotNumber,
+        latest_block_roots_length: int) -> Hash32:
     """
-    Return the element from ``target_list`` by the ``target_slot`` number,
-    where the the element should be at ``target_slot - slot_relative_position``th
-    element of the given ``target_list``.
+    Return the block root at a recent ``slot``.
     """
-    target_list_length = len(target_list)
-
-    if target_slot < slot_relative_position:
+    if state_slot > slot + latest_block_roots_length:
         raise ValueError(
-            "target_slot (%s) should be greater than or equal to slot_relative_position (%s)" %
-            (target_slot, slot_relative_position)
+            "state.slot (%s) should be less than or equal to "
+            "(slot + latest_block_roots_length) (%s)" %
+            (state_slot, slot + latest_block_roots_length)
         )
-
-    if target_slot >= slot_relative_position + target_list_length:
+    if slot >= state_slot:
         raise ValueError(
-            "target_slot (%s) should be less than "
-            "slot_relative_position (%s) + target_list_length (%s)" %
-            (target_slot, slot_relative_position, target_list_length)
+            "slot (%s) should be less than state.slot (%s)" %
+            (slot, state_slot)
         )
-    return target_list[target_slot - slot_relative_position]
+    return latest_block_roots[slot % latest_block_roots_length]
 
 
-#
-# Get block root
-#
 def get_block_root(
-        latest_block_roots: Sequence[Hash32],
-        current_slot: SlotNumber,
-        slot: SlotNumber) -> Hash32:
+        state: 'BeaconState',
+        slot: SlotNumber,
+        latest_block_roots_length: int) -> Hash32:
     """
-    Returns the block root at a recent ``slot``.
+    Return the block root at a recent ``slot``.
     """
-    slot_relative_position = SlotNumber(current_slot - len(latest_block_roots))
-    return _get_element_from_recent_list(
-        latest_block_roots,
+    return _get_block_root(
+        state.latest_block_roots,
+        state.slot,
         slot,
-        slot_relative_position,
+        latest_block_roots_length,
     )
 
 
@@ -116,21 +111,21 @@ def _get_shard_committees_at_slot(
         shard_committees_at_slots: Sequence[Sequence[ShardCommittee]],
         slot: SlotNumber,
         epoch_length: int) -> Iterable[ShardCommittee]:
-    if len(shard_committees_at_slots) != epoch_length * 2:
+
+    earliest_slot_in_array = state_slot - (state_slot % epoch_length) - epoch_length
+
+    if earliest_slot_in_array > slot:
         raise ValueError(
-            "Length of shard_committees_at_slots != epoch_length * 2"
-            "\texpected: %s, found: %s" % (
-                epoch_length * 2, len(shard_committees_at_slots)
-            )
+            "earliest_slot_in_array (%s) should be less than or equal to slot (%s)" %
+            (earliest_slot_in_array, slot + slot)
+        )
+    if slot >= earliest_slot_in_array + epoch_length * 2:
+        raise ValueError(
+            "slot (%s) should be less than earliest_slot_in_array + epoch_length * 2 (%s)" %
+            (slot, earliest_slot_in_array + epoch_length * 2)
         )
 
-    slot_relative_position = SlotNumber(state_slot - epoch_length)
-
-    yield from _get_element_from_recent_list(
-        shard_committees_at_slots,
-        slot,
-        slot_relative_position,
-    )
+    return shard_committees_at_slots[slot - earliest_slot_in_array]
 
 
 def get_shard_committees_at_slot(state: 'BeaconState',

eth/beacon/state_machines/forks/serenity/operations.py

@@ -26,6 +26,7 @@ def process_attestations(state: BeaconState,
             attestation,
             config.EPOCH_LENGTH,
             config.MIN_ATTESTATION_INCLUSION_DELAY,
+            config.LATEST_BLOCK_ROOTS_LENGTH,
         )
 
     # update_latest_attestations

eth/beacon/state_machines/forks/serenity/validation.py

@@ -72,7 +72,8 @@ def validate_serenity_proposer_signature(state: BeaconState,
 def validate_serenity_attestation(state: Type[BeaconState],
                                   attestation: Attestation,
                                   epoch_length: int,
-                                  min_attestation_inclusion_delay: int) -> None:
+                                  min_attestation_inclusion_delay: int,
+                                  latest_block_roots_length: int) -> None:
     """
     Validate the given ``attestation``.
     Raise ``ValidationError`` if it's invalid.
@@ -96,9 +97,9 @@ def validate_serenity_attestation(state: Type[BeaconState],
     validate_serenity_attestation_justified_block_root(
         attestation.data,
         justified_block_root=get_block_root(
-            state.latest_block_roots,
-            current_slot=state.slot,
+            state=state,
             slot=attestation.data.justified_slot,
+            latest_block_roots_length=latest_block_roots_length,
         ),
     )
 

tests/beacon/state_machines/forks/test_serenity_operations.py

@@ -46,9 +46,9 @@ def create_mock_signed_attestations_at_slot(state,
                 shard=shard_committee.shard,
                 justified_slot=state.previous_justified_slot,
                 justified_block_root=get_block_root(
-                    state.latest_block_roots,
-                    state.slot,
+                    state,
                     state.previous_justified_slot,
+                    config.LATEST_BLOCK_ROOTS_LENGTH,
                 ),
                 latest_crosslink_root=latest_crosslink_root,
                 shard_block_root=ZERO_HASH32,

tests/beacon/test_helpers.py

@@ -34,17 +34,16 @@
 from eth.beacon.types.states import BeaconState
 from eth.beacon.types.validator_records import ValidatorRecord
 from eth.beacon.helpers import (
-    _get_element_from_recent_list,
+    _get_block_root,
+    _get_shard_committees_at_slot,
     get_active_validator_indices,
     get_attestation_participants,
     get_beacon_proposer_index,
-    get_block_root,
     get_effective_balance,
     get_domain,
     get_fork_version,
     get_new_shuffling,
     get_new_validator_registry_delta_chain_tip,
-    _get_shard_committees_at_slot,
     get_block_committees_info,
     get_pubkey_for_indices,
     generate_aggregate_pubkeys,
@@ -88,56 +87,29 @@ def get_sample_shard_committees_at_slots(num_slot,
 
 def generate_mock_latest_block_roots(
         genesis_block,
-        current_block_number,
-        epoch_length):
-    chain_length = (current_block_number // epoch_length + 1) * epoch_length
+        current_slot,
+        epoch_length,
+        latest_block_roots_length):
+    assert current_slot < latest_block_roots_length
+
+    chain_length = (current_slot // epoch_length + 1) * epoch_length
     blocks = get_pseudo_chain(chain_length, genesis_block)
     latest_block_roots = [
-        b'\x00' * 32
-        for i
-        in range(epoch_length * 2 - current_block_number)
-    ] + [block.root for block in blocks[:current_block_number]]
+        block.hash
+        for block in blocks[:current_slot]
+    ] + [
+        ZERO_HASH32
+        for _ in range(latest_block_roots_length - current_slot)
+    ]
     return blocks, latest_block_roots
 
 
-@pytest.mark.parametrize(
-    (
-        'target_list,target_slot,slot_relative_position,result'
-    ),
-    [
-        ([i for i in range(5)], 10, 7, 3),
-        ([], 1, 1, ValueError()),
-        # target_slot < slot_relative_position
-        ([i for i in range(5)], 1, 2, ValueError()),
-        # target_slot >= slot_relative_position + target_list_length
-        ([i for i in range(5)], 6, 1, ValueError()),
-    ],
-)
-def test_get_element_from_recent_list(target_list,
-                                      target_slot,
-                                      slot_relative_position,
-                                      result):
-    if isinstance(result, Exception):
-        with pytest.raises(ValueError):
-            _get_element_from_recent_list(
-                target_list,
-                target_slot,
-                slot_relative_position,
-            )
-    else:
-        assert result == _get_element_from_recent_list(
-            target_list,
-            target_slot,
-            slot_relative_position,
-        )
-
-
 #
 # Get block rootes
 #
 @pytest.mark.parametrize(
     (
-        'current_block_number,target_slot,success'
+        'current_slot,target_slot,success'
     ),
     [
         (10, 0, True),
@@ -148,30 +120,34 @@ def test_get_element_from_recent_list(target_list,
         (128, 128, False),
     ],
 )
-def test_get_block_root(current_block_number,
+def test_get_block_root(current_slot,
                         target_slot,
                         success,
                         epoch_length,
+                        latest_block_roots_length,
                         sample_block):
     blocks, latest_block_roots = generate_mock_latest_block_roots(
         sample_block,
-        current_block_number,
+        current_slot,
         epoch_length,
+        latest_block_roots_length,
     )
 
     if success:
-        block_root = get_block_root(
+        block_root = _get_block_root(
             latest_block_roots,
-            current_block_number,
+            current_slot,
             target_slot,
+            latest_block_roots_length,
         )
         assert block_root == blocks[target_slot].root
     else:
         with pytest.raises(ValueError):
-            get_block_root(
+            _get_block_root(
                 latest_block_roots,
-                current_block_number,
+                current_slot,
                 target_slot,
+                latest_block_roots_length,
             )
 
 
@@ -207,16 +183,6 @@ def test_get_block_root(current_block_number,
             64,
             True,
         ),
-        # The length of shard_committees_at_slots != epoch_length * 2
-        (
-            100,
-            64,
-            64,
-            127,
-            10,
-            0,
-            False,
-        ),
         # slot is too small
         (
             100,