forkchoice store on top of any state now

specs/phase0/fork-choice.md

@@ -14,7 +14,7 @@
   - [Helpers](#helpers)
     - [`LatestMessage`](#latestmessage)
     - [`Store`](#store)
-    - [`get_genesis_store`](#get_genesis_store)
+    - [`get_forkchoice_store`](#get_forkchoice_store)
     - [`get_slots_since_genesis`](#get_slots_since_genesis)
     - [`get_current_slot`](#get_current_slot)
     - [`compute_slots_since_epoch_start`](#compute_slots_since_epoch_start)
@@ -38,7 +38,7 @@ This document is the beacon chain fork choice spec, part of Ethereum 2.0 Phase 0
 
 ## Fork choice
 
-The head block root associated with a `store` is defined as `get_head(store)`. At genesis, let `store = get_genesis_store(genesis_state)` and update `store` by running:
+The head block root associated with a `store` is defined as `get_head(store)`. At genesis, let `store = get_checkpoint_store(genesis_state)` and update `store` by running:
 
 - `on_tick(time)` whenever `time > store.time` where `time` is the current Unix time
 - `on_block(block)` whenever a block `block: SignedBeaconBlock` is received
@@ -79,29 +79,35 @@ class Store(object):
     justified_checkpoint: Checkpoint
     finalized_checkpoint: Checkpoint
     best_justified_checkpoint: Checkpoint
-    blocks: Dict[Root, BeaconBlock] = field(default_factory=dict)
+    blocks: Dict[Root, BeaconBlockHeader] = field(default_factory=dict)
     block_states: Dict[Root, BeaconState] = field(default_factory=dict)
     checkpoint_states: Dict[Checkpoint, BeaconState] = field(default_factory=dict)
     latest_messages: Dict[ValidatorIndex, LatestMessage] = field(default_factory=dict)
 ```
 
-#### `get_genesis_store`
+#### `get_forkchoice_store`
+
+The provided anchor-state will be regarded as a trusted state, to not roll back beyond.
+This should be the genesis state for a full client.
 
 ```python
-def get_genesis_store(genesis_state: BeaconState) -> Store:
-    genesis_block = BeaconBlock(state_root=hash_tree_root(genesis_state))
-    root = hash_tree_root(genesis_block)
-    justified_checkpoint = Checkpoint(epoch=GENESIS_EPOCH, root=root)
-    finalized_checkpoint = Checkpoint(epoch=GENESIS_EPOCH, root=root)
+def get_forkchoice_store(anchor_state: BeaconState) -> Store:
+    anchor_block_header = anchor_state.latest_block_header.copy()
+    if anchor_block_header.state_root == Bytes32():
+        anchor_block_header.state_root = hash_tree_root(anchor_state)
+    anchor_root = hash_tree_root(anchor_block_header)
+    anchor_epoch = get_current_epoch(anchor_state)
+    justified_checkpoint = Checkpoint(epoch=anchor_epoch, root=anchor_root)
+    finalized_checkpoint = Checkpoint(epoch=anchor_epoch, root=anchor_root)
     return Store(
-        time=genesis_state.genesis_time,
-        genesis_time=genesis_state.genesis_time,
+        time=anchor_state.genesis_time,
+        genesis_time=anchor_state.genesis_time,
         justified_checkpoint=justified_checkpoint,
         finalized_checkpoint=finalized_checkpoint,
         best_justified_checkpoint=justified_checkpoint,
-        blocks={root: genesis_block},
-        block_states={root: genesis_state.copy()},
-        checkpoint_states={justified_checkpoint: genesis_state.copy()},
+        blocks={anchor_root: anchor_block_header},
+        block_states={anchor_root: anchor_state.copy()},
+        checkpoint_states={justified_checkpoint: anchor_state.copy()},
     )
 ```
 

tests/core/pyspec/eth2spec/test/fork_choice/test_get_head.py

@@ -34,7 +34,7 @@ def add_attestation_to_store(spec, store, attestation):
 @spec_state_test
 def test_genesis(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     genesis_block = spec.BeaconBlock(state_root=state.hash_tree_root())
     assert spec.get_head(store) == spec.hash_tree_root(genesis_block)
 
@@ -43,7 +43,7 @@ def test_genesis(spec, state):
 @spec_state_test
 def test_chain_no_attestations(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     genesis_block = spec.BeaconBlock(state_root=state.hash_tree_root())
     assert spec.get_head(store) == spec.hash_tree_root(genesis_block)
 
@@ -66,7 +66,7 @@ def test_split_tie_breaker_no_attestations(spec, state):
     genesis_state = state.copy()
 
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     genesis_block = spec.BeaconBlock(state_root=state.hash_tree_root())
     assert spec.get_head(store) == spec.hash_tree_root(genesis_block)
 
@@ -94,7 +94,7 @@ def test_shorter_chain_but_heavier_weight(spec, state):
     genesis_state = state.copy()
 
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     genesis_block = spec.BeaconBlock(state_root=state.hash_tree_root())
     assert spec.get_head(store) == spec.hash_tree_root(genesis_block)
 
@@ -123,7 +123,7 @@ def test_shorter_chain_but_heavier_weight(spec, state):
 def test_filtered_block_tree(spec, state):
     # Initialization
     genesis_state_root = state.hash_tree_root()
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     genesis_block = spec.BeaconBlock(state_root=genesis_state_root)
 
     # transition state past initial couple of epochs

tests/core/pyspec/eth2spec/test/fork_choice/test_on_attestation.py

@@ -27,7 +27,7 @@ def run_on_attestation(spec, state, store, attestation, valid=True):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_current_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     spec.on_tick(store, store.time + spec.SECONDS_PER_SLOT * 2)
 
     block = build_empty_block_for_next_slot(spec, state)
@@ -46,7 +46,7 @@ def test_on_attestation_current_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_previous_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     spec.on_tick(store, store.time + spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH)
 
     block = build_empty_block_for_next_slot(spec, state)
@@ -65,7 +65,7 @@ def test_on_attestation_previous_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_past_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
 
     # move time forward 2 epochs
     time = store.time + 2 * spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
@@ -87,7 +87,7 @@ def test_on_attestation_past_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_mismatched_target_and_slot(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     spec.on_tick(store, store.time + spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH)
 
     block = build_empty_block_for_next_slot(spec, state)
@@ -110,7 +110,7 @@ def test_on_attestation_mismatched_target_and_slot(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_target_not_in_store(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
     spec.on_tick(store, time)
 
@@ -131,7 +131,7 @@ def test_on_attestation_target_not_in_store(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_beacon_block_not_in_store(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
     spec.on_tick(store, time)
 
@@ -159,7 +159,7 @@ def test_on_attestation_beacon_block_not_in_store(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_future_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 3 * spec.SECONDS_PER_SLOT
     spec.on_tick(store, time)
 
@@ -179,7 +179,7 @@ def test_on_attestation_future_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_future_block(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = spec.SECONDS_PER_SLOT * 5
     spec.on_tick(store, time)
 
@@ -199,7 +199,7 @@ def test_on_attestation_future_block(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_same_slot(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 1 * spec.SECONDS_PER_SLOT
     spec.on_tick(store, time)
 
@@ -215,7 +215,7 @@ def test_on_attestation_same_slot(spec, state):
 @with_all_phases
 @spec_state_test
 def test_on_attestation_invalid_attestation(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 3 * spec.SECONDS_PER_SLOT
     spec.on_tick(store, time)
 

tests/core/pyspec/eth2spec/test/fork_choice/test_on_block.py

@@ -36,7 +36,7 @@ def apply_next_epoch_with_attestations(spec, state, store):
 @spec_state_test
 def test_basic(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
     assert store.time == time
@@ -60,7 +60,7 @@ def test_basic(spec, state):
 @spec_state_test
 def test_on_block_checkpoints(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
 
@@ -86,7 +86,7 @@ def test_on_block_checkpoints(spec, state):
 @spec_state_test
 def test_on_block_future_block(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
 
     # do not tick time
 
@@ -100,7 +100,7 @@ def test_on_block_future_block(spec, state):
 @spec_state_test
 def test_on_block_bad_parent_root(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
 
@@ -120,7 +120,7 @@ def test_on_block_bad_parent_root(spec, state):
 @spec_state_test
 def test_on_block_before_finalized(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
 
@@ -139,7 +139,7 @@ def test_on_block_before_finalized(spec, state):
 @spec_state_test
 def test_on_block_update_justified_checkpoint_within_safe_slots(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
 
@@ -170,7 +170,7 @@ def test_on_block_update_justified_checkpoint_within_safe_slots(spec, state):
 @spec_state_test
 def test_on_block_outside_safe_slots_and_multiple_better_justified(spec, state):
     # Initialization
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     time = 100
     spec.on_tick(store, time)
 

tests/core/pyspec/eth2spec/test/fork_choice/test_on_tick.py

@@ -19,14 +19,14 @@ def run_on_tick(spec, store, time, new_justified_checkpoint=False):
 @with_all_phases
 @spec_state_test
 def test_basic(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     run_on_tick(spec, store, store.time + 1)
 
 
 @with_all_phases
 @spec_state_test
 def test_update_justified_single(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     seconds_per_epoch = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
 
     store.best_justified_checkpoint = spec.Checkpoint(
@@ -40,7 +40,7 @@ def test_update_justified_single(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_update_same_slot_at_epoch_boundary(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     seconds_per_epoch = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
 
     store.best_justified_checkpoint = spec.Checkpoint(
@@ -57,7 +57,7 @@ def test_no_update_same_slot_at_epoch_boundary(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_update_not_epoch_boundary(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
 
     store.best_justified_checkpoint = spec.Checkpoint(
         epoch=store.justified_checkpoint.epoch + 1,
@@ -70,7 +70,7 @@ def test_no_update_not_epoch_boundary(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_update_new_justified_equal_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     seconds_per_epoch = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
 
     store.best_justified_checkpoint = spec.Checkpoint(
@@ -89,7 +89,7 @@ def test_no_update_new_justified_equal_epoch(spec, state):
 @with_all_phases
 @spec_state_test
 def test_no_update_new_justified_later_epoch(spec, state):
-    store = spec.get_genesis_store(state)
+    store = spec.get_forkchoice_store(state)
     seconds_per_epoch = spec.SECONDS_PER_SLOT * spec.SLOTS_PER_EPOCH
 
     store.best_justified_checkpoint = spec.Checkpoint(