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Active registry roots #1104

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Active registry roots #1104

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Active registry roots
JustinDrake May 21, 2019
8acfe92
Update 0_beacon-chain.md
JustinDrake May 21, 2019
519d7d4
Update 0_beacon-chain.md
JustinDrake May 29, 2019
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87 changes: 51 additions & 36 deletions specs/core/0_beacon-chain.md
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Original file line number Diff line number Diff line change
Expand Up @@ -31,6 +31,7 @@
- [`DepositData`](#depositdata)
- [`BeaconBlockHeader`](#beaconblockheader)
- [`Validator`](#validator)
- [`ActiveRegistry`](#activeregistry)
- [`PendingAttestation`](#pendingattestation)
- [`HistoricalBatch`](#historicalbatch)
- [Beacon operations](#beacon-operations)
Expand Down Expand Up @@ -62,17 +63,17 @@
- [`decrease_balance`](#decrease_balance)
- [`get_epoch_committee_count`](#get_epoch_committee_count)
- [`get_shard_delta`](#get_shard_delta)
- [`get_epoch_start_shard`](#get_epoch_start_shard)
- [`get_start_shard`](#get_start_shard)
- [`get_attestation_data_slot`](#get_attestation_data_slot)
- [`get_block_root_at_slot`](#get_block_root_at_slot)
- [`get_block_root`](#get_block_root)
- [`get_randao_mix`](#get_randao_mix)
- [`get_active_index_root`](#get_active_index_root)
- [`get_active_registry_root`](#get_active_registry_root)
- [`generate_seed`](#generate_seed)
- [`get_beacon_proposer_index`](#get_beacon_proposer_index)
- [`verify_merkle_branch`](#verify_merkle_branch)
- [`get_shuffled_index`](#get_shuffled_index)
- [`compute_committee`](#compute_committee)
- [`get_committee_indices`](#get_committee_indices)
- [`get_crosslink_committee`](#get_crosslink_committee)
- [`get_attesting_indices`](#get_attesting_indices)
- [`int_to_bytes`](#int_to_bytes)
Expand Down Expand Up @@ -179,10 +180,11 @@ These configurations are updated for releases, but may be out of sync during `de

| Name | Value | Unit |
| - | - | :-: |
| `MIN_DEPOSIT_AMOUNT` | `2**0 * 10**9` (= 1,000,000,000) | Gwei |
| `MAX_EFFECTIVE_BALANCE` | `2**5 * 10**9` (= 32,000,000,000) | Gwei |
| `EJECTION_BALANCE` | `2**4 * 10**9` (= 16,000,000,000) | Gwei |
| `EFFECTIVE_BALANCE_INCREMENT` | `2**0 * 10**9` (= 1,000,000,000) | Gwei |
| `GWEI_PER_ETH` | `10**9` (= 1,000,000,000) | Gwei |
| `MIN_DEPOSIT_AMOUNT` | `2**0 * GWEI_PER_ETH` (= 1,000,000,000) | Gwei |
| `MAX_EFFECTIVE_BALANCE` | `2**5 * GWEI_PER_ETH` (= 32,000,000,000) | Gwei |
| `EJECTION_BALANCE` | `2**4 * GWEI_PER_ETH` (= 16,000,000,000) | Gwei |
| `EFFECTIVE_BALANCE_INCREMENT` | `2**0 * GWEI_PER_ETH` (= 1,000,000,000) | Gwei |

### Initial values

Expand Down Expand Up @@ -216,7 +218,7 @@ These configurations are updated for releases, but may be out of sync during `de
| 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_ACTIVE_REGISTRY_ROOTS_LENGTH` | `2**13` (= 8,192) | epochs | ~36 days |
| `LATEST_SLASHED_EXIT_LENGTH` | `2**13` (= 8,192) | epochs | ~36 days |

### Reward and penalty quotients
Expand Down Expand Up @@ -397,6 +399,15 @@ The types are defined topologically to aid in facilitating an executable version
}
```

#### `ActiveRegistry`

```python
[{
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'pubkeys': ['bytes48'],
'compact_validators': ['uint64'],
}, SHARD_COUNT]
```

#### `PendingAttestation`

```python
Expand Down Expand Up @@ -577,7 +588,7 @@ 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_active_registry_roots': ['bytes32', LATEST_ACTIVE_REGISTRY_ROOTS_LENGTH],
'latest_slashed_balances': ['uint64', LATEST_SLASHED_EXIT_LENGTH],
'latest_block_header': BeaconBlockHeader,
'historical_roots': ['bytes32'],
Expand Down Expand Up @@ -748,10 +759,10 @@ def get_shard_delta(state: BeaconState, epoch: Epoch) -> int:
return min(get_epoch_committee_count(state, epoch), SHARD_COUNT - SHARD_COUNT // SLOTS_PER_EPOCH)
```

### `get_epoch_start_shard`
### `get_start_shard`

```python
def get_epoch_start_shard(state: BeaconState, epoch: Epoch) -> Shard:
def get_start_shard(state: BeaconState, epoch: Epoch) -> Shard:
assert epoch <= get_current_epoch(state) + 1
check_epoch = get_current_epoch(state) + 1
shard = (state.latest_start_shard + get_shard_delta(state, get_current_epoch(state))) % SHARD_COUNT
Expand All @@ -766,7 +777,7 @@ def get_epoch_start_shard(state: BeaconState, epoch: Epoch) -> Shard:
```python
def get_attestation_data_slot(state: BeaconState, data: AttestationData) -> Slot:
committee_count = get_epoch_committee_count(state, data.target_epoch)
offset = (data.crosslink.shard + SHARD_COUNT - get_epoch_start_shard(state, data.target_epoch)) % SHARD_COUNT
offset = (data.crosslink.shard + SHARD_COUNT - get_start_shard(state, data.target_epoch)) % SHARD_COUNT
return get_epoch_start_slot(data.target_epoch) + offset // (committee_count // SLOTS_PER_EPOCH)
```

Expand Down Expand Up @@ -805,17 +816,24 @@ def get_randao_mix(state: BeaconState,
return state.latest_randao_mixes[epoch % LATEST_RANDAO_MIXES_LENGTH]
```

### `get_active_index_root`
### `get_active_registry_root`
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```python
def get_active_index_root(state: BeaconState,
epoch: Epoch) -> Bytes32:
def get_active_registry_root(state: BeaconState) -> Bytes32:
"""
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].
Return the active registry root for the current epoch.
"""
return state.latest_active_index_roots[epoch % LATEST_ACTIVE_INDEX_ROOTS_LENGTH]
epoch = get_current_epoch(state)
active_registry = ActiveRegistry()
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for committee_number in range(get_epoch_committee_count(state, epoch)):
shard = (get_start_shard(state, epoch) + committee_number) % SHARD_COUNT
for index in get_crosslink_committee(state, epoch, shard):
validator = validator_registry[index]
active_registry[shard].pubkeys.append(validator.pubkey)
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@djrtwo djrtwo May 27, 2019 •
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You're sorting validators by their crosslink committee shard. This isn't going to be particularly useful for light clients unless we merge the two committees.

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That's a good point. Maybe we want to wait until phase 1 to put this light-client infrastructure in place.

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The active_index_roots in combination with the historical randaomixes being in state was generic enough to serve proofs about the historic crosslink and persistent committees.
If we go this new path, we should either wait or intend to put both committees in the registry root.

# index (top 7 bytes) + slashed (8th bit) + effective_balance (bottom 7 bits)
compact_validator = index << 8 + validator.slashed << 7 + validator.effective_balance // GWEI_PER_ETH
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Suggested change
compact_validator = index << 8 + validator.slashed << 7 + validator.effective_balance // GWEI_PER_ETH
compact_validator = index << 8 + validator.slashed << 7 + validator.effective_balance // EFFECTIVE_BALANCE_INCREMENT

Same value, but it might not be in other configurations / future. So let's use the increment constant instead.

active_registry[shard].compact_validators.append(compact_validator)
return hash_tree_root(active_registry)
```

### `generate_seed`
Expand All @@ -828,7 +846,7 @@ def generate_seed(state: BeaconState,
"""
return hash(
get_randao_mix(state, epoch + LATEST_RANDAO_MIXES_LENGTH - MIN_SEED_LOOKAHEAD) +
get_active_index_root(state, epoch) +
state.latest_active_registry_roots[epoch % LATEST_ACTIVE_REGISTRY_ROOTS_LENGTH] +
int_to_bytes(epoch, length=32)
)
```
Expand All @@ -843,7 +861,7 @@ def get_beacon_proposer_index(state: BeaconState) -> ValidatorIndex:
epoch = get_current_epoch(state)
committees_per_slot = get_epoch_committee_count(state, epoch) // SLOTS_PER_EPOCH
offset = committees_per_slot * (state.slot % SLOTS_PER_EPOCH)
shard = (get_epoch_start_shard(state, epoch) + offset) % SHARD_COUNT
shard = (get_start_shard(state, epoch) + offset) % SHARD_COUNT
first_committee = get_crosslink_committee(state, epoch, shard)
MAX_RANDOM_BYTE = 2**8 - 1
seed = generate_seed(state, epoch)
Expand Down Expand Up @@ -898,10 +916,10 @@ def get_shuffled_index(index: ValidatorIndex, index_count: int, seed: Bytes32) -
return index
```

### `compute_committee`
### `get_committee_indices`

```python
def compute_committee(indices: List[ValidatorIndex], seed: Bytes32, index: int, count: int) -> List[ValidatorIndex]:
def get_committee_indices(indices: List[ValidatorIndex], seed: Bytes32, index: int, count: int) -> List[ValidatorIndex]:
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start = (len(indices) * index) // count
end = (len(indices) * (index + 1)) // count
return [indices[get_shuffled_index(i, len(indices), seed)] for i in range(start, end)]
Expand All @@ -911,10 +929,10 @@ def compute_committee(indices: List[ValidatorIndex], seed: Bytes32, index: int,

```python
def get_crosslink_committee(state: BeaconState, epoch: Epoch, shard: Shard) -> List[ValidatorIndex]:
return compute_committee(
return get_committee_indices(
indices=get_active_validator_indices(state, epoch),
seed=generate_seed(state, epoch),
index=(shard + SHARD_COUNT - get_epoch_start_shard(state, epoch)) % SHARD_COUNT,
index=(shard + SHARD_COUNT - get_start_shard(state, epoch)) % SHARD_COUNT,
count=get_epoch_committee_count(state, epoch),
)
```
Expand Down Expand Up @@ -1206,10 +1224,9 @@ def get_genesis_beacon_state(deposits: List[Deposit], genesis_time: int, genesis
validator.activation_eligibility_epoch = GENESIS_EPOCH
validator.activation_epoch = GENESIS_EPOCH

# 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):
state.latest_active_index_roots[index] = genesis_active_index_root
# Populate active registry roots
for index in range(LATEST_ACTIVE_REGISTRY_ROOTS_LENGTH):
state.latest_active_registry_roots[index] = get_active_registry_root(state)

return state
```
Expand Down Expand Up @@ -1391,7 +1408,7 @@ def process_crosslinks(state: BeaconState) -> None:
state.previous_crosslinks = [c for c in state.current_crosslinks]
for epoch in (get_previous_epoch(state), get_current_epoch(state)):
for offset in range(get_epoch_committee_count(state, epoch)):
shard = (get_epoch_start_shard(state, epoch) + offset) % SHARD_COUNT
shard = (get_start_shard(state, epoch) + offset) % SHARD_COUNT
crosslink_committee = get_crosslink_committee(state, epoch, shard)
winning_crosslink, attesting_indices = get_winning_crosslink_and_attesting_indices(state, epoch, shard)
if 3 * get_total_balance(state, attesting_indices) >= 2 * get_total_balance(state, crosslink_committee):
Expand Down Expand Up @@ -1461,7 +1478,7 @@ def get_crosslink_deltas(state: BeaconState) -> Tuple[List[Gwei], List[Gwei]]:
penalties = [0 for index in range(len(state.validator_registry))]
epoch = get_previous_epoch(state)
for offset in range(get_epoch_committee_count(state, epoch)):
shard = (get_epoch_start_shard(state, epoch) + offset) % SHARD_COUNT
shard = (get_start_shard(state, epoch) + offset) % SHARD_COUNT
crosslink_committee = get_crosslink_committee(state, epoch, shard)
winning_crosslink, attesting_indices = get_winning_crosslink_and_attesting_indices(state, epoch, shard)
attesting_balance = get_total_balance(state, attesting_indices)
Expand Down Expand Up @@ -1554,11 +1571,9 @@ def process_final_updates(state: BeaconState) -> None:
validator.effective_balance = min(balance - balance % EFFECTIVE_BALANCE_INCREMENT, MAX_EFFECTIVE_BALANCE)
# 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
state.latest_active_index_roots[index_root_position] = hash_tree_root(
get_active_validator_indices(state, next_epoch + ACTIVATION_EXIT_DELAY)
)
# Set active registry root
active_registry_index = (next_epoch + ACTIVATION_EXIT_DELAY) % LATEST_ACTIVE_REGISTRY_ROOTS_LENGTH
state.latest_active_registry_roots[active_registry_index] = get_active_registry_root(state)
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# Set total slashed balances
state.latest_slashed_balances[next_epoch % LATEST_SLASHED_EXIT_LENGTH] = (
state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH]
Expand Down