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Increase length of historical vectors #1109

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Increase length of historical vectors #1109

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66 changes: 25 additions & 41 deletions specs/core/0_beacon-chain.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@
- [Gwei values](#gwei-values)
- [Initial values](#initial-values)
- [Time parameters](#time-parameters)
- [State list lengths](#state-list-lengths)
- [Reward and penalty quotients](#reward-and-penalty-quotients)
- [Max operations per block](#max-operations-per-block)
- [Signature domains](#signature-domains)
Expand Down Expand Up @@ -208,16 +207,7 @@ These configurations are updated for releases, but may be out of sync during `de
| `PERSISTENT_COMMITTEE_PERIOD` | `2**11` (= 2,048) | epochs | 9 days |
| `MAX_EPOCHS_PER_CROSSLINK` | `2**6` (= 64) | epochs | ~7 hours |
| `MIN_EPOCHS_TO_INACTIVITY_PENALTY` | `2**2` (= 4) | epochs | 25.6 minutes |

* `MAX_EPOCHS_PER_CROSSLINK` should be a small constant times `SHARD_COUNT // SLOTS_PER_EPOCH`

### State list lengths

| Name | Value | Unit | Duration |
| - | - | :-: | :-: |
| `LATEST_RANDAO_MIXES_LENGTH` | `2**13` (= 8,192) | epochs | ~36 days |
| `LATEST_ACTIVE_INDEX_ROOTS_LENGTH` | `2**13` (= 8,192) | epochs | ~36 days |
| `LATEST_SLASHED_EXIT_LENGTH` | `2**13` (= 8,192) | epochs | ~36 days |
| `EPOCHS_PER_HISTORICAL_VECTOR ` | `2**16` (= 65,536) | epochs | ~0.8 years |

### Reward and penalty quotients

Expand Down Expand Up @@ -558,7 +548,7 @@ The types are defined topologically to aid in facilitating an executable version
'balances': ['uint64'],

# Randomness and committees
'latest_randao_mixes': ['bytes32', LATEST_RANDAO_MIXES_LENGTH],
'latest_randao_mixes': ['bytes32', EPOCHS_PER_HISTORICAL_VECTOR],
'latest_start_shard': 'uint64',

# Finality
Expand All @@ -577,8 +567,8 @@ The types are defined topologically to aid in facilitating an executable version
'previous_crosslinks': [Crosslink, SHARD_COUNT],
'latest_block_roots': ['bytes32', SLOTS_PER_HISTORICAL_ROOT],
'latest_state_roots': ['bytes32', SLOTS_PER_HISTORICAL_ROOT],
'latest_active_index_roots': ['bytes32', LATEST_ACTIVE_INDEX_ROOTS_LENGTH],
'latest_slashed_balances': ['uint64', LATEST_SLASHED_EXIT_LENGTH],
'latest_active_index_roots': ['bytes32', EPOCHS_PER_HISTORICAL_VECTOR],
'latest_slashed_balances': ['uint64', EPOCHS_PER_HISTORICAL_VECTOR],
'latest_block_header': BeaconBlockHeader,
'historical_roots': ['bytes32'],

Expand Down Expand Up @@ -800,9 +790,9 @@ def get_randao_mix(state: BeaconState,
epoch: Epoch) -> Bytes32:
"""
Return the randao mix at a recent ``epoch``.
``epoch`` expected to be between (current_epoch - LATEST_RANDAO_MIXES_LENGTH, current_epoch].
``epoch`` expected to be between (current_epoch - EPOCHS_PER_HISTORICAL_VECTOR, current_epoch].
"""
return state.latest_randao_mixes[epoch % LATEST_RANDAO_MIXES_LENGTH]
return state.latest_randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
```

### `get_active_index_root`
Expand All @@ -813,9 +803,9 @@ def get_active_index_root(state: BeaconState,
"""
Return the index root at a recent ``epoch``.
``epoch`` expected to be between
(current_epoch - LATEST_ACTIVE_INDEX_ROOTS_LENGTH + ACTIVATION_EXIT_DELAY, current_epoch + ACTIVATION_EXIT_DELAY].
(current_epoch - EPOCHS_PER_HISTORICAL_VECTOR + ACTIVATION_EXIT_DELAY, current_epoch + ACTIVATION_EXIT_DELAY].
"""
return state.latest_active_index_roots[epoch % LATEST_ACTIVE_INDEX_ROOTS_LENGTH]
return state.latest_active_index_roots[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
```

### `generate_seed`
Expand All @@ -827,7 +817,7 @@ def generate_seed(state: BeaconState,
Generate a seed for the given ``epoch``.
"""
return hash(
get_randao_mix(state, epoch + LATEST_RANDAO_MIXES_LENGTH - MIN_SEED_LOOKAHEAD) +
get_randao_mix(state, epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD) +
get_active_index_root(state, epoch) +
int_to_bytes(epoch, length=32)
)
Expand Down Expand Up @@ -1157,9 +1147,9 @@ def slash_validator(state: BeaconState,
current_epoch = get_current_epoch(state)
initiate_validator_exit(state, slashed_index)
state.validator_registry[slashed_index].slashed = True
state.validator_registry[slashed_index].withdrawable_epoch = current_epoch + LATEST_SLASHED_EXIT_LENGTH
state.validator_registry[slashed_index].withdrawable_epoch = current_epoch + EPOCHS_PER_HISTORICAL_VECTOR
slashed_balance = state.validator_registry[slashed_index].effective_balance
state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH] += slashed_balance
state.latest_slashed_balances[current_epoch % EPOCHS_PER_HISTORICAL_VECTOR] += slashed_balance

proposer_index = get_beacon_proposer_index(state)
if whistleblower_index is None:
Expand Down Expand Up @@ -1208,7 +1198,7 @@ def get_genesis_beacon_state(deposits: List[Deposit], genesis_time: int, genesis

# Populate latest_active_index_roots
genesis_active_index_root = hash_tree_root(get_active_validator_indices(state, GENESIS_EPOCH))
for index in range(LATEST_ACTIVE_INDEX_ROOTS_LENGTH):
for index in range(EPOCHS_PER_HISTORICAL_VECTOR):
state.latest_active_index_roots[index] = genesis_active_index_root

return state
Expand Down Expand Up @@ -1524,12 +1514,12 @@ def process_slashings(state: BeaconState) -> None:
total_balance = get_total_balance(state, active_validator_indices)

# Compute `total_penalties`
total_at_start = state.latest_slashed_balances[(current_epoch + 1) % LATEST_SLASHED_EXIT_LENGTH]
total_at_end = state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH]
total_at_start = state.latest_slashed_balances[(current_epoch + 1) % EPOCHS_PER_HISTORICAL_VECTOR]
total_at_end = state.latest_slashed_balances[current_epoch % EPOCHS_PER_HISTORICAL_VECTOR]
total_penalties = total_at_end - total_at_start

for index, validator in enumerate(state.validator_registry):
if validator.slashed and current_epoch == validator.withdrawable_epoch - LATEST_SLASHED_EXIT_LENGTH // 2:
if validator.slashed and current_epoch == validator.withdrawable_epoch - EPOCHS_PER_HISTORICAL_VECTOR // 2:
penalty = max(
validator.effective_balance * min(total_penalties * 3, total_balance) // total_balance,
validator.effective_balance // MIN_SLASHING_PENALTY_QUOTIENT
Expand All @@ -1555,16 +1545,16 @@ def process_final_updates(state: BeaconState) -> None:
# Update start shard
state.latest_start_shard = (state.latest_start_shard + get_shard_delta(state, current_epoch)) % SHARD_COUNT
# Set active index root
index_root_position = (next_epoch + ACTIVATION_EXIT_DELAY) % LATEST_ACTIVE_INDEX_ROOTS_LENGTH
index_root_position = (next_epoch + ACTIVATION_EXIT_DELAY) % EPOCHS_PER_HISTORICAL_VECTOR
state.latest_active_index_roots[index_root_position] = hash_tree_root(
get_active_validator_indices(state, next_epoch + ACTIVATION_EXIT_DELAY)
)
# Set total slashed balances
state.latest_slashed_balances[next_epoch % LATEST_SLASHED_EXIT_LENGTH] = (
state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH]
state.latest_slashed_balances[next_epoch % EPOCHS_PER_HISTORICAL_VECTOR] = (
state.latest_slashed_balances[current_epoch % EPOCHS_PER_HISTORICAL_VECTOR]
)
# Set randao mix
state.latest_randao_mixes[next_epoch % LATEST_RANDAO_MIXES_LENGTH] = get_randao_mix(state, current_epoch)
state.latest_randao_mixes[next_epoch % EPOCHS_PER_HISTORICAL_VECTOR] = get_randao_mix(state, current_epoch)
# Set historical root accumulator
if next_epoch % (SLOTS_PER_HISTORICAL_ROOT // SLOTS_PER_EPOCH) == 0:
historical_batch = HistoricalBatch(
Expand Down Expand Up @@ -1612,19 +1602,13 @@ def process_block_header(state: BeaconState, block: BeaconBlock) -> None:

```python
def process_randao(state: BeaconState, body: BeaconBlockBody) -> None:
epoch = get_current_epoch(state)
# Verify RANDAO reveal
proposer = state.validator_registry[get_beacon_proposer_index(state)]
# Verify that the provided randao value is valid
assert bls_verify(
proposer.pubkey,
hash_tree_root(get_current_epoch(state)),
body.randao_reveal,
get_domain(state, DOMAIN_RANDAO),
)
# Mix it in
state.latest_randao_mixes[get_current_epoch(state) % LATEST_RANDAO_MIXES_LENGTH] = (
xor(get_randao_mix(state, get_current_epoch(state)),
hash(body.randao_reveal))
)
assert bls_verify(proposer.pubkey, hash_tree_root(epoch), body.randao_reveal, get_domain(state, DOMAIN_RANDAO))
# Mix in RANDAO reveal
mix = xor(get_randao_mix(state, epoch), hash(body.randao_reveal))
state.latest_randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR] = mix
```

#### Eth1 data
Expand Down