Cleanups

specs/core/0_fork-choice.md

@@ -11,13 +11,12 @@
     - [Constants](#constants)
         - [Time parameters](#time-parameters)
     - [Fork choice](#fork-choice)
-        - [Containers](#containers)
+        - [Helpers](#helpers)
             - [`Target`](#target)
             - [`Store`](#store)
-        - [Helpers](#helpers)
             - [`get_genesis_store`](#get_genesis_store)
             - [`get_ancestor`](#get_ancestor)
-            - [`get_attesting_balance_from_store`](#get_attesting_balance_from_store)
+            - [`get_latest_attesting_balance`](#get_latest_attesting_balance)
             - [`get_head`](#get_head)
         - [Handlers](#handlers)
             - [`on_tick`](#on_tick)
@@ -51,9 +50,9 @@ The head block root associated with a `store` is defined as `get_head(store)`. A
 1) **Leap seconds**: Slots will last `SECONDS_PER_SLOT + 1` or `SECONDS_PER_SLOT - 1` seconds around leap seconds.
 2) **Honest clocks**: Honest nodes are assumed to have clocks synchronized within `SECONDS_PER_SLOT` seconds of each other.
 3) **Eth1 data**: The large `ETH1_FOLLOW_DISTANCE` specified in the [honest validator document](https://github.com/ethereum/eth2.0-specs/blob/dev/specs/validator/0_beacon-chain-validator.md) should ensure that `state.latest_eth1_data` of the canonical Ethereum 2.0 chain remains consistent with the canonical Ethereum 1.0 chain. If not, emergency manual intervention will be required.
-4) **Manual forks**: Manual forks may arbitrarily change the fork choice rule but are expected to be enacted at epoch transitions, with the fork details reflected in `state.fork`. 
+4) **Manual forks**: Manual forks may arbitrarily change the fork choice rule but are expected to be enacted at epoch transitions, with the fork details reflected in `state.fork`.
 
-### Containers
+### Helpers
 
 #### `Target`
 
@@ -61,7 +60,7 @@ The head block root associated with a `store` is defined as `get_head(store)`. A
 @dataclass
 class Target(object):
     epoch: Epoch
-    root: Bytes32
+    root: Hash
 ```
 
 #### `Store`
@@ -69,38 +68,36 @@ class Target(object):
 ```python
 @dataclass
 class Store(object):
-    blocks: Dict[Bytes32, BeaconBlock] = field(default_factory=dict)
+    blocks: Dict[Hash, BeaconBlock] = field(default_factory=dict)
-    states: Dict[Bytes32, BeaconState] = field(default_factory=dict)
+    states: Dict[Hash, BeaconState] = field(default_factory=dict)
     time: int = 0
     latest_targets: Dict[ValidatorIndex, Target] = field(default_factory=dict)
-    justified_root: Bytes32 = ZERO_HASH
+    justified_root: Hash = ZERO_HASH
-    finalized_root: Bytes32 = ZERO_HASH
+    finalized_root: Hash = ZERO_HASH
 ```
 
-### Helpers
-
 #### `get_genesis_store`
 
 ```python
 def get_genesis_store(genesis_state: BeaconState) -> Store:
     genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))
     root = signing_root(genesis_block)
-    return Store(blocks={root: genesis_block}, states={root: genesis_state}, finalized_root=root, justified_root=root)
+    return Store(blocks={root: genesis_block}, states={root: genesis_state}, justified_root=root, finalized_root=root)
 ```
 
 #### `get_ancestor`
 
 ```python
-def get_ancestor(store: Store, root: Bytes32, slot: Slot) -> Bytes32:
+def get_ancestor(store: Store, root: Hash, slot: Slot) -> Hash:
     block = store.blocks[root]
     assert block.slot >= slot
     return root if block.slot == slot else get_ancestor(store, block.parent_root, slot)
 ```
 
-#### `get_attesting_balance_from_store`
+#### `get_latest_attesting_balance`
 
 ```python
-def get_attesting_balance_from_store(store: Store, root: Bytes32) -> Gwei:
+def get_latest_attesting_balance(store: Store, root: Hash) -> Gwei:
     state = store.states[store.justified_root]
     active_indices = get_active_validator_indices(state.validator_registry, slot_to_epoch(state.slot))
     return Gwei(sum(
@@ -112,15 +109,15 @@ def get_attesting_balance_from_store(store: Store, root: Bytes32) -> Gwei:
 #### `get_head`
 
 ```python
-def get_head(store: Store) -> Bytes32:
+def get_head(store: Store) -> Hash:
     # Execute the LMD-GHOST fork choice
     head = store.justified_root
     while True:
         children = [root for root in store.blocks.keys() if store.blocks[root].parent_root == head]
         if len(children) == 0:
             return head
-        # Sort by attesting balance with ties broken lexicographically
+        # Sort by latest attesting balance with ties broken lexicographically
-        head = max(children, key=lambda root: (get_attesting_balance_from_store(store, root), root))
+        head = max(children, key=lambda root: (get_latest_attesting_balance(store, root), root))
 ```
 
 ### Handlers
@@ -147,13 +144,14 @@ def on_block(store: Store, block: BeaconBlock) -> None:
     state = state_transition(pre_state, block)
     # Add new state to the store
     store.states[signing_root(block)] = state
-    # Update justified and finalized blocks
+    # Update justified block root
-    if state.finalized_epoch > slot_to_epoch(store.blocks[store.finalized_root].slot):
-        store.finalized_root = state.finalized_root
     if state.current_justified_epoch > slot_to_epoch(store.blocks[store.justified_root].slot):
         store.justified_root = state.current_justified_root
     elif state.previous_justified_epoch > slot_to_epoch(store.blocks[store.justified_root].slot):
         store.justified_root = state.previous_justified_root
+    # Update finalized block root
+    if state.finalized_epoch > slot_to_epoch(store.blocks[store.finalized_root].slot):
+        store.finalized_root = state.finalized_root
 ```
 
 #### `on_attestation`
@@ -165,8 +163,5 @@ def on_attestation(store: Store, attestation: Attestation) -> None:
     validate_indexed_attestation(state, indexed_attestation)
     for i in indexed_attestation.custody_bit_0_indices + indexed_attestation.custody_bit_1_indices:
         if i not in store.latest_targets or attestation.data.target_epoch > store.latest_targets[i].epoch:
-            store.latest_targets[i] = Target(
+            store.latest_targets[i] = Target(attestation.data.target_epoch, attestation.data.target_root)
-                epoch=attestation.data.target_epoch,
-                root=attestation.data.target_root,
-            )
 ```