Implement light client friendliness changes

eth2/beacon/enums.py

@@ -6,11 +6,6 @@ class ValidatorStatusFlags(IntEnum):
     WITHDRAWABLE = 2
 
 
-class ValidatorRegistryDeltaFlag(IntEnum):
-    ACTIVATION = 0
-    EXIT = 1
-
-
 class SignatureDomain(IntEnum):
     DOMAIN_DEPOSIT = 0
     DOMAIN_ATTESTATION = 1

eth2/beacon/helpers.py

@@ -23,6 +23,9 @@
 from eth2._utils.numeric import (
     bitwise_xor,
 )
+from eth2.beacon._utils.hash import (
+    hash_eth2,
+)
 from eth2.beacon._utils.random import (
     shuffle,
     split,
@@ -43,6 +46,7 @@
     ValidatorIndex,
 )
 from eth2.beacon.validation import (
+    validate_epoch_for_active_index_root,
     validate_slot_for_state_slot,
 )
 
@@ -108,6 +112,7 @@ def get_randao_mix(state: 'BeaconState',
     """
     Return the randao mix at a recent ``slot``.
     """
+    # TODO: update to epoch version
     assert state.slot < slot + latest_randao_mixes_length
     assert slot <= state.slot
     return state.latest_randao_mixes[slot % latest_randao_mixes_length]
@@ -243,7 +248,7 @@ def get_crosslink_committees_at_slot(
             target_committee_size=target_committee_size,
         )
 
-        seed = state.previous_epoch_randao_mix
+        seed = state.previous_epoch_seed
         shuffling_slot = state.previous_epoch_calculation_slot
         shuffling_start_shard = state.previous_epoch_start_shard
     else:
@@ -253,7 +258,7 @@ def get_crosslink_committees_at_slot(
             epoch_length=epoch_length,
             target_committee_size=target_committee_size,
         )
-        seed = state.current_epoch_randao_mix
+        seed = state.current_epoch_seed
         shuffling_slot = state.current_epoch_calculation_slot
         shuffling_start_shard = state.current_epoch_start_shard
 
@@ -279,9 +284,46 @@ def get_crosslink_committees_at_slot(
         )
 
 
-#
-# Get proposer position
-#
+def get_active_index_root(state: 'BeaconState',
+                          slot: SlotNumber,
+                          epoch_length: int,
+                          latest_index_roots_length: int) -> Hash32:
+    """
+    Return the index root at a recent ``slot``.
+    """
+    state_epoch = state.slot // epoch_length
+    given_epoch = slot // epoch_length
+
+    validate_epoch_for_active_index_root(state_epoch, given_epoch, latest_index_roots_length)
+
+    return state.latest_index_roots[given_epoch % latest_index_roots_length]
+
+
+def generate_seed(state: 'BeaconState',
+                  slot: SlotNumber,
+                  epoch_length: int,
+                  seed_lookahead: int,
+                  latest_index_roots_length: int,
+                  latest_randao_mixes_length: int) -> Hash32:
+    """
+    Generate a seed for the given ``slot``.
+
+    TODO: it's slot version, will be changed to epoch version.
+    """
+    randao_mix = get_randao_mix(
+        state,
+        SlotNumber(slot - seed_lookahead),
+        latest_randao_mixes_length=latest_randao_mixes_length,
+    )
+    active_index_root = get_active_index_root(
+        state,
+        slot,
+        epoch_length=epoch_length,
+        latest_index_roots_length=latest_index_roots_length,
+    )
+
+    return hash_eth2(randao_mix + active_index_root)
+
 
 def get_beacon_proposer_index(state: 'BeaconState',
                               slot: SlotNumber,
@@ -506,3 +548,14 @@ def is_surround_vote(attestation_data_1: 'AttestationData',
         (attestation_data_2.justified_slot + 1 == attestation_data_2.slot) and
         (attestation_data_2.slot < attestation_data_1.slot)
     )
+
+
+def get_entry_exit_effect_slot(slot: SlotNumber,
+                               epoch_length: int,
+                               entry_exit_delay: int) -> SlotNumber:
+    """
+    An entry or exit triggered in the slot given by the input takes effect at
+    the slot given by the output.
+    """
+    # TODO: update to epoch version
+    return SlotNumber((slot - slot % epoch_length) + epoch_length + entry_exit_delay)

eth2/beacon/on_startup.py

@@ -66,8 +66,8 @@ def get_initial_beacon_state(*,
                              genesis_start_shard: ShardNumber,
                              shard_count: int,
                              latest_block_roots_length: int,
+                             latest_index_roots_length: int,
                              epoch_length: int,
-                             target_committee_size: int,
                              max_deposit: Ether,
                              latest_penalized_exit_length: int,
                              latest_randao_mixes_length: int,
@@ -87,7 +87,6 @@ def get_initial_beacon_state(*,
         validator_balances=(),
         validator_registry_update_slot=genesis_slot,
         validator_registry_exit_count=0,
-        validator_registry_delta_chain_tip=ZERO_HASH32,
 
         # Randomness and committees
         latest_randao_mixes=tuple(ZERO_HASH32 for _ in range(latest_randao_mixes_length)),
@@ -101,8 +100,8 @@ def get_initial_beacon_state(*,
         current_epoch_start_shard=genesis_start_shard,
         previous_epoch_calculation_slot=genesis_slot,
         current_epoch_calculation_slot=genesis_slot,
-        previous_epoch_randao_mix=ZERO_HASH32,
-        current_epoch_randao_mix=ZERO_HASH32,
+        previous_epoch_seed=ZERO_HASH32,
+        current_epoch_seed=ZERO_HASH32,
 
         # Custody challenges
         custody_challenges=(),
@@ -119,6 +118,7 @@ def get_initial_beacon_state(*,
             for _ in range(shard_count)
         ]),
         latest_block_roots=tuple(ZERO_HASH32 for _ in range(latest_block_roots_length)),
+        latest_index_roots=tuple(ZERO_HASH32 for _ in range(latest_index_roots_length)),
         latest_penalized_balances=tuple(
             Gwei(0)
             for _ in range(latest_penalized_exit_length)
@@ -154,8 +154,9 @@ def get_initial_beacon_state(*,
             state = activate_validator(
                 state,
                 validator_index,
-                genesis=True,
+                is_genesis=True,
                 genesis_slot=genesis_slot,
+                epoch_length=epoch_length,
                 entry_exit_delay=entry_exit_delay,
             )
 

eth2/beacon/state_machines/configs.py

@@ -24,6 +24,7 @@
         ('BEACON_CHAIN_SHARD_NUMBER', ShardNumber),
         ('MAX_CASPER_VOTES', int),
         ('LATEST_BLOCK_ROOTS_LENGTH', int),
+        ('LATEST_INDEX_ROOTS_LENGTH', int),
         ('LATEST_RANDAO_MIXES_LENGTH', int),
         ('LATEST_PENALIZED_EXIT_LENGTH', int),
         # EMPTY_SIGNATURE is defined in constants.py

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

@@ -19,6 +19,7 @@
     BEACON_CHAIN_SHARD_NUMBER=ShardNumber(2**64 - 1),
     MAX_CASPER_VOTES=2**10,  # (= 1,024) votes
     LATEST_BLOCK_ROOTS_LENGTH=2**13,  # (= 8,192) block roots
+    LATEST_INDEX_ROOTS_LENGTH=2**13,  # (= 8,192) index roots
     LATEST_RANDAO_MIXES_LENGTH=2**13,  # (= 8,192) randao mixes
     LATEST_PENALIZED_EXIT_LENGTH=2**13,  # (= 8,192) randao mixes
     # Deposit contract

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

@@ -8,16 +8,20 @@
 from eth2._utils.tuple import (
     update_tuple_item,
 )
+from eth2.beacon._utils.hash import (
+    hash_eth2,
+)
+from eth2.beacon import helpers
 from eth2.beacon.helpers import (
+    get_active_validator_indices,
     get_current_epoch_committee_count_per_slot,
-    get_randao_mix,
 )
 from eth2.beacon.types.states import BeaconState
 from eth2.beacon.state_machines.configs import BeaconConfig
 
 
 #
-# Validator Registry
+# Validator registry and shuffling seed data
 #
 def _check_if_update_validator_registry(state: BeaconState,
                                         config: BeaconConfig) -> Tuple[bool, int]:
@@ -48,13 +52,47 @@ def update_validator_registry(state: BeaconState) -> BeaconState:
     return state
 
 
+def _update_latest_index_roots(state: BeaconState,
+                               config: BeaconConfig) -> BeaconState:
+    """
+    Return the BeaconState with updated `latest_index_roots`.
+    """
+    next_epoch = state.next_epoch(config.EPOCH_LENGTH)
+
+    # TODO: chanege to hash_tree_root
+    active_validator_indices = get_active_validator_indices(
+        state.validator_registry,
+        # TODO: change to `per-epoch` version
+        state.slot,
+    )
+    index_root = hash_eth2(
+        b''.join(
+            [
+                index.to_bytes(32, 'big')
+                for index in active_validator_indices
+            ]
+        )
+    )
+
+    latest_index_roots = update_tuple_item(
+        state.latest_index_roots,
+        next_epoch % config.LATEST_INDEX_ROOTS_LENGTH,
+        index_root,
+    )
+
+    return state.copy(
+        latest_index_roots=latest_index_roots,
+    )
+
+
 def process_validator_registry(state: BeaconState,
                                config: BeaconConfig) -> BeaconState:
     state = state.copy(
         previous_epoch_calculation_slot=state.current_epoch_calculation_slot,
         previous_epoch_start_shard=state.current_epoch_start_shard,
-        previous_epoch_randao_mix=state.current_epoch_randao_mix,
+        previous_epoch_seed=state.current_epoch_seed,
     )
+    state = _update_latest_index_roots(state, config)
 
     need_to_update, num_shards_in_committees = _check_if_update_validator_registry(state, config)
 
@@ -71,12 +109,19 @@ def process_validator_registry(state: BeaconState,
                 state.current_epoch_start_shard + num_shards_in_committees
             ) % config.SHARD_COUNT,
         )
+
+        # The `helpers.generate_seed` function is only present to provide an entry point
+        # for mocking this out in tests.
+        current_epoch_seed = helpers.generate_seed(
+            state=state,
+            slot=state.current_epoch_calculation_slot,
+            epoch_length=config.EPOCH_LENGTH,
+            seed_lookahead=config.SEED_LOOKAHEAD,
+            latest_index_roots_length=config.LATEST_INDEX_ROOTS_LENGTH,
+            latest_randao_mixes_length=config.LATEST_RANDAO_MIXES_LENGTH,
+        )
         state = state.copy(
-            current_epoch_randao_mix=get_randao_mix(
-                state,
-                state.current_epoch_calculation_slot - config.SEED_LOOKAHEAD,
-                config.LATEST_RANDAO_MIXES_LENGTH,
-            ),
+            current_epoch_seed=current_epoch_seed,
         )
     else:
         epochs_since_last_registry_change = (
@@ -88,13 +133,22 @@ def process_validator_registry(state: BeaconState,
             state = state.copy(
                 current_epoch_calculation_slot=state.slot,
             )
+
+            # The `helpers.generate_seed` function is only present to provide an entry point
+            # for mocking this out in tests.
+            current_epoch_seed = helpers.generate_seed(
+                state=state,
+                slot=state.current_epoch_calculation_slot,
+                epoch_length=config.EPOCH_LENGTH,
+                seed_lookahead=config.SEED_LOOKAHEAD,
+                latest_index_roots_length=config.LATEST_INDEX_ROOTS_LENGTH,
+                latest_randao_mixes_length=config.LATEST_RANDAO_MIXES_LENGTH,
+            )
             state = state.copy(
-                current_epoch_randao_mix=get_randao_mix(
-                    state,
-                    state.current_epoch_calculation_slot - config.SEED_LOOKAHEAD,
-                    config.LATEST_RANDAO_MIXES_LENGTH,
-                ),
+                current_epoch_seed=current_epoch_seed,
             )
+        else:
+            pass
 
     return state
 

eth2/beacon/tools/builder/initializer.py

@@ -112,8 +112,8 @@ def create_mock_genesis(
         genesis_start_shard=config.GENESIS_START_SHARD,
         shard_count=config.SHARD_COUNT,
         latest_block_roots_length=config.LATEST_BLOCK_ROOTS_LENGTH,
+        latest_index_roots_length=config.LATEST_INDEX_ROOTS_LENGTH,
         epoch_length=config.EPOCH_LENGTH,
-        target_committee_size=config.TARGET_COMMITTEE_SIZE,
         max_deposit=config.MAX_DEPOSIT,
         latest_penalized_exit_length=config.LATEST_PENALIZED_EXIT_LENGTH,
         latest_randao_mixes_length=config.LATEST_RANDAO_MIXES_LENGTH,