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Updated cryptarchia total stake inference spec #133

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104 changes: 53 additions & 51 deletions cryptarchia/cryptarchia.py
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Original file line number Diff line number Diff line change
Expand Up @@ -73,36 +73,36 @@ class Config:
def cryptarchia_v0_0_1(initial_total_active_stake) -> "Config":
return Config(
k=2160,
active_slot_coeff=0.05,
active_slot_coeff=1 / 30,
epoch_stake_distribution_stabilization=3,
epoch_period_nonce_buffer=3,
epoch_period_nonce_stabilization=4,
initial_total_active_stake=initial_total_active_stake,
total_active_stake_learning_rate=0.8,
total_active_stake_learning_rate=1.0,
time=TimeConfig(
slot_duration=1,
chain_start_time=0,
),
)

@property
@functools.cached_property
def base_period_length(self) -> int:
return int(floor(self.k / self.active_slot_coeff))

@property
@functools.cached_property
def epoch_relative_nonce_slot(self) -> int:
return (
self.epoch_stake_distribution_stabilization + self.epoch_period_nonce_buffer
) * self.base_period_length

@property
@functools.cached_property
def epoch_length(self) -> int:
return (
self.epoch_relative_nonce_slot
+ self.epoch_period_nonce_stabilization * self.base_period_length
)

@property
@functools.cached_property
def s(self):
"""
The Security Paramater. This paramter controls how many slots one must
Expand Down Expand Up @@ -162,6 +162,7 @@ def encode_sk(self) -> bytes:
def encode_pk(self) -> bytes:
return int.to_bytes(self.pk, length=32, byteorder="big")

@functools.cached_property
def commitment(self) -> Hash:
value_bytes = int.to_bytes(self.value, length=32, byteorder="big")
return Hash(
Expand All @@ -174,8 +175,9 @@ def commitment(self) -> Hash:
self.zone_id,
)

@functools.cached_property
def nullifier(self) -> Hash:
return Hash(b"NOMOS_NOTE_NF", self.commitment(), self.encode_sk())
return Hash(b"NOMOS_NOTE_NF", self.commitment, self.encode_sk())


@dataclass
Expand All @@ -188,7 +190,7 @@ def epoch_nonce_contribution(self) -> Hash:
return Hash(
b"NOMOS_NONCE_CONTRIB",
self.slot.encode(),
self.note.commitment(),
self.note.commitment,
self.note.encode_sk(),
)

Expand All @@ -199,8 +201,8 @@ def verify(
return (
slot == self.slot
and parent == self.parent
and self.note.commitment() in commitments
and self.note.nullifier() not in nullifiers
and self.note.commitment in commitments
and self.note.nullifier not in nullifiers
)


Expand All @@ -217,6 +219,7 @@ class BlockHeader:
# as serialized in the format specified by the 'HEADER' rule in 'messages.abnf'.
#
# The following code is to be considered as a reference implementation, mostly to be used for testing.
@functools.cached_property
def id(self) -> Hash:
return Hash(
b"BLOCK_ID",
Expand All @@ -231,7 +234,7 @@ def id(self) -> Hash:
)

def __hash__(self):
return hash(self.id())
return hash(self.id)


@dataclass
Expand Down Expand Up @@ -271,7 +274,7 @@ def replace(self, **kwarg) -> "LedgerState":
return replace(self, **kwarg)

def apply(self, block: BlockHeader):
assert block.parent == self.block.id()
assert block.parent == self.block.id

self.nonce = Hash(
b"EPOCH_NONCE",
Expand Down Expand Up @@ -317,12 +320,12 @@ class Follower:
def __init__(self, genesis_state: LedgerState, config: Config):
self.config = config
self.forks: list[Hash] = []
self.local_chain = genesis_state.block.id()
self.local_chain = genesis_state.block.id
self.genesis_state = genesis_state
self.ledger_state = {genesis_state.block.id(): genesis_state.copy()}
self.ledger_state = {genesis_state.block.id: genesis_state.copy()}
self.epoch_state = {}
self.state = State.BOOTSTRAPPING
self.lib = genesis_state.block.id() # Last immutable block, initially the genesis block
self.lib = genesis_state.block.id # Last immutable block, initially the genesis block

def to_online(self):
"""
Expand Down Expand Up @@ -359,22 +362,22 @@ def validate_header(self, block: BlockHeader):
raise InvalidLeaderProof

def on_block(self, block: BlockHeader):
if block.id() in self.ledger_state:
if block.id in self.ledger_state:
logger.warning("dropping already processed block")
return

self.validate_header(block)

new_state = self.ledger_state[block.parent].copy()
new_state.apply(block)
self.ledger_state[block.id()] = new_state
self.ledger_state[block.id] = new_state

if block.parent == self.local_chain:
# simply extending the local chain
self.local_chain = block.id()
self.local_chain = block.id
else:
# otherwise, this block creates a fork
self.forks.append(block.id())
self.forks.append(block.id)

# remove any existing fork that is superceded by this block
if block.parent in self.forks:
Expand All @@ -389,7 +392,6 @@ def on_block(self, block: BlockHeader):
if self.state == State.ONLINE:
self.update_lib()


# Update the lib, and prune forks that do not descend from it.
def update_lib(self):
"""
Expand All @@ -401,7 +403,7 @@ def update_lib(self):
return
# prune forks that do not descend from the last immutable block, this is needed to avoid Genesis rule to roll back
# past the LIB
self.lib = next(islice(iter_chain(self.local_chain, self.ledger_state), self.config.k, None), self.genesis_state).block.id()
self.lib = next(islice(iter_chain(self.local_chain, self.ledger_state), self.config.k, None), self.genesis_state).block.id
self.forks = [
f for f in self.forks if is_ancestor(self.lib, f, self.ledger_state)
]
Expand All @@ -411,7 +413,6 @@ def update_lib(self):
if is_ancestor(self.lib, k, self.ledger_state) or is_ancestor(k, self.lib, self.ledger_state)
}


# Evaluate the fork choice rule and return the chain we should be following
def fork_choice(self) -> Hash:
if self.state == State.BOOTSTRAPPING:
Expand Down Expand Up @@ -450,20 +451,18 @@ def state_at_slot_beginning(self, tip: Hash, slot: Slot) -> LedgerState:
def epoch_start_slot(self, epoch) -> Slot:
return Slot(epoch.epoch * self.config.epoch_length)

def stake_distribution_snapshot(self, epoch, tip: Hash):
def stake_distribution_snapshot_slot(self, epoch):
# stake distribution snapshot happens at the beginning of the previous epoch,
# i.e. for epoch e, the snapshot is taken at the last block of epoch e-2
slot = Slot(epoch.prev().epoch * self.config.epoch_length)
return self.state_at_slot_beginning(tip, slot)
return self.epoch_start_slot(epoch.prev())

def nonce_snapshot(self, epoch, tip):
def nonce_snapshot_slot(self, epoch):
# nonce snapshot happens partway through the previous epoch after the
# stake distribution has stabilized
slot = Slot(
return Slot(
self.config.epoch_relative_nonce_slot
+ self.epoch_start_slot(epoch.prev()).absolute_slot
)
return self.state_at_slot_beginning(tip, slot)

def compute_epoch_state(self, epoch: Epoch, tip: Hash) -> EpochState:
if epoch.epoch == 0:
Expand All @@ -473,18 +472,21 @@ def compute_epoch_state(self, epoch: Epoch, tip: Hash) -> EpochState:
inferred_total_active_stake=self.config.initial_total_active_stake,
)

stake_distribution_snapshot = self.stake_distribution_snapshot(epoch, tip)
nonce_snapshot = self.nonce_snapshot(epoch, tip)

# we memoize epoch states to avoid recursion killing our performance
memo_block_id = nonce_snapshot.block.id()
if state := self.epoch_state.get((epoch, memo_block_id)):
if state := self.epoch_state.get((epoch, tip)):
return state

nonce_slot = self.nonce_snapshot_slot(epoch)
stake_distribution_slot = self.stake_distribution_snapshot_slot(epoch)

stake_distribution_snapshot = self.state_at_slot_beginning(
tip, stake_distribution_slot
)
nonce_snapshot = self.state_at_slot_beginning(tip, nonce_slot)

# To update our inference of total stake, we need the prior estimate which
# was calculated last epoch. Thus we recurse here to retreive the previous
# estimate of total stake.
prev_epoch = self.compute_epoch_state(epoch.prev(), tip)
prev_epoch = self.compute_epoch_state(epoch.prev(), nonce_snapshot.block.id)
inferred_total_active_stake = self._infer_total_active_stake(
prev_epoch, nonce_snapshot, stake_distribution_snapshot
)
Expand All @@ -495,7 +497,7 @@ def compute_epoch_state(self, epoch: Epoch, tip: Hash) -> EpochState:
inferred_total_active_stake=inferred_total_active_stake,
)

self.epoch_state[(epoch, memo_block_id)] = state
self.epoch_state[(epoch, tip)] = state
return state

def _infer_total_active_stake(
Expand All @@ -509,19 +511,19 @@ def _infer_total_active_stake(
# Since we need a stable inference of total stake for the start of this epoch,
# we limit our look back period to the start of last epoch until when the nonce
# snapshot was taken.
block_proposals_last_epoch = (
period_block_density = (
nonce_snapshot.leader_count - stake_distribution_snapshot.leader_count
)
T = self.config.epoch_relative_nonce_slot
mean_blocks_per_slot = block_proposals_last_epoch / T
expected_blocks_per_slot = np.log(1 / (1 - self.config.active_slot_coeff))
blocks_per_slot_err = expected_blocks_per_slot - mean_blocks_per_slot
h = (
self.config.total_active_stake_learning_rate
* prev_epoch.inferred_total_active_stake
/ expected_blocks_per_slot
)
return int(prev_epoch.inferred_total_active_stake - h * blocks_per_slot_err)
# Use epoch_relative_nonce_slot as this is the actual observation window
# (the slot range from stake_distribution_snapshot to nonce_snapshot)
period = self.config.epoch_relative_nonce_slot
f = self.config.active_slot_coeff
beta = self.config.total_active_stake_learning_rate
total_stake_estimate = prev_epoch.inferred_total_active_stake

slot_activation_error = 1 - period_block_density / (period * f)
coefficient = total_stake_estimate * beta
return max(1, int(total_stake_estimate - coefficient * slot_activation_error))

def blocks_by_slot(self, from_slot: Slot) -> Generator[BlockHeader, None, None]:
# Returns blocks in the given range of slots in order of slot
Expand Down Expand Up @@ -564,7 +566,7 @@ def _is_slot_leader(self, epoch: EpochState, slot: Slot):
b"LEAD",
epoch.nonce(),
slot.encode(),
self.note.commitment(),
self.note.commitment,
self.note.encode_sk(),
)
ticket = int.from_bytes(ticket)
Expand Down Expand Up @@ -605,7 +607,7 @@ def is_ancestor(a: Hash, b: Hash, states: Dict[Hash, LedgerState]) -> bool:
Returns True if `a` is an ancestor of `b` in the chain.
"""
for state in iter_chain(b, states):
if state.block.id() == a:
if state.block.id == a:
return True
return False

Expand All @@ -623,7 +625,7 @@ def common_prefix_depth(
try:
a_block = next(a_blocks)
a_suffix.append(a_block)
a_block_id = a_block.id()
a_block_id = a_block.id
if a_block_id in seen:
# we had seen this block from the fork chain
return (
Expand All @@ -640,7 +642,7 @@ def common_prefix_depth(
try:
b_block = next(b_blocks)
b_suffix.append(b_block)
b_block_id = b_block.id()
b_block_id = b_block.id
if b_block_id in seen:
# we had seen the fork in the local chain
return (
Expand Down
21 changes: 9 additions & 12 deletions cryptarchia/sync.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -39,8 +39,8 @@ def sync(local: Follower, peers: list[Follower], checkpoint: LedgerState | None
num_blocks += 1
# Reject blocks that have been rejected in the past
# or whose parent has been rejected.
if {block.id(), block.parent} & rejected_blocks:
rejected_blocks.add(block.id())
if {block.id, block.parent} & rejected_blocks:
rejected_blocks.add(block.id)
continue

try:
Expand All @@ -49,7 +49,7 @@ def sync(local: Follower, peers: list[Follower], checkpoint: LedgerState | None
except ParentNotFound:
orphans.add(block)
except Exception:
rejected_blocks.add(block.id())
rejected_blocks.add(block.id)

# Finish the sync process if no block has been fetched,
# which means that no peer has a tip ahead of the local tip.
Expand All @@ -63,14 +63,11 @@ def sync(local: Follower, peers: list[Follower], checkpoint: LedgerState | None
# Skip the orphan block if it has been processed during the previous backfillings
# (i.e. if it has been already added to the local block tree).
# Or, skip if it has been rejected during the previous backfillings.
if (
orphan.id() not in local.ledger_state
and orphan.id() not in rejected_blocks
):
if orphan.id not in local.ledger_state and orphan.id not in rejected_blocks:
try:
backfill_fork(local, orphan, block_fetcher)
except InvalidBlockFromBackfillFork as e:
rejected_blocks.update(block.id() for block in e.invalid_suffix)
rejected_blocks.update(block.id for block in e.invalid_suffix)


def backfill_fork(
Expand All @@ -83,7 +80,7 @@ def backfill_fork(

suffix = find_missing_part(
local,
block_fetcher.fetch_chain_backward(fork_tip.id(), local),
block_fetcher.fetch_chain_backward(fork_tip.id, local),
)

# Add blocks in the fork suffix with applying fork choice rule.
Expand All @@ -105,7 +102,7 @@ def find_missing_part(

suffix: list[BlockHeader] = []
for block in fork:
if block.id() in local.ledger_state:
if block.id in local.ledger_state:
break
suffix.append(block)
suffix.reverse()
Expand Down Expand Up @@ -167,15 +164,15 @@ def fetch_chain_backward(
# First, try to iterate the chain from the local block tree.
for block in iter_chain_blocks(id, local.ledger_state):
yield block
if block.id() == local.genesis_state.block.id():
if block.id == local.genesis_state.block.id:
return
id = block.parent

# Try to continue by fetching the remaining blocks from the peers
for peer in self.peers:
for block in iter_chain_blocks(id, peer.ledger_state):
yield block
if block.id() == local.genesis_state.block.id():
if block.id == local.genesis_state.block.id:
return
id = block.parent

Expand Down
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