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FCR: thread balances through active validator iteration #99

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Merged
dapplion merged 1 commit into from
Jul 1, 2026
Merged

FCR: thread balances through active validator iteration #99

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6 changes: 4 additions & 2 deletions consensus/fast_confirmation/src/balance_source.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -57,12 +57,14 @@ impl BalanceSourceData {
self.effective_balances.get(val_idx).copied().unwrap_or(0)
}

pub(crate) fn unslashed_and_active_indices(&self) -> impl Iterator<Item = usize> + '_ {
pub(crate) fn unslashed_and_active_indices(&self) -> impl Iterator<Item = (usize, u64)> + '_ {
self.effective_balances
.iter()
.copied()
.enumerate()
.filter_map(|(i, balance)| {
(*balance > 0 && !self.slashed.get(i).copied().unwrap_or(false)).then_some(i)
(balance > 0 && !self.slashed.get(i).copied().unwrap_or(false))
.then_some((i, balance))
})
}

Expand Down
46 changes: 22 additions & 24 deletions consensus/fast_confirmation/src/lib.rs
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Expand Up @@ -666,11 +666,6 @@ impl FastConfirmationRule {
// -----------------------------------------------------------------------

/// Spec: `get_block_support_between_slots`.
/// Counts weight of validators whose latest vote is for EXACTLY `block_root`
/// (not descendants) and whose committee assignment is in [start_slot, end_slot].
/// Equivalent to the spec's `participants` set, but iterates validators with latest
/// messages and tests committee membership with precomputed head assignments instead of
/// materializing all committee participants for the slot range.
fn get_block_support_between_slots(
&self,
balance_source: &BalanceSourceData,
Expand All @@ -680,10 +675,17 @@ impl FastConfirmationRule {
votes: &[VoteTracker],
equivocating_indices: &BTreeSet<u64>,
) -> Result<u64, Error> {
// Spec: sum effective balance of validators that:
// - Are assigned to attest in a committee in the `range(start_slot, end_slot + 1)`
// - Are active in `balance_source` tracked here as `balance > 0`
// - Are not slashed in `balance_source` tracked here as `slashed == false`
// - Do not belong to the `store.equivocating_indices` set
// - Their vote is for exactly `block_root`
let mut score = 0u64;
for (val_idx, vote) in votes.iter().enumerate() {
let balance = balance_source.unslashed_balance(val_idx);
// `balance > 0` is the spec's active-and-unslashed validator filter.
for (val_idx, balance) in balance_source.unslashed_and_active_indices() {
let Some(vote) = votes.get(val_idx) else {
continue;
};
if balance > 0
&& self
.head_assignments
Expand Down Expand Up @@ -892,9 +894,9 @@ impl FastConfirmationRule {
equivocating_indices: &BTreeSet<u64>,
) -> Result<u64, Error> {
let mut score = 0u64;
// Spec: Sum the balance of validators that:
// Spec: Sum the effective balance of validators that:
// - Belong to the `store.equivocating_indices` set
// - As assigned to attest in a committee in the `range(start_slot, end_slot + 1)`
// - Are assigned to attest in a committee in the `range(start_slot, end_slot + 1)`
// - Are active in `balance_source` tracked here as `balance > 0`
for &idx in equivocating_indices {
let idx = idx as usize;
Expand Down Expand Up @@ -988,33 +990,29 @@ impl FastConfirmationRule {
let mut balance_by_vote_checkpoint =
optimizations::RootBalanceMap::<(Hash256, Epoch)>::new();

// Spec: iterate `unslashed_and_active_indices`; zero roots mean no latest message.
for val_idx in self.head_balance_source.unslashed_and_active_indices() {
// Spec: sum the effective balance of validators that:
// - Are active the current epoch
// - Are not slashed in the current epoch
// - Don't belong in the equivocating_indices set
// - Have a vote for the current target
let mut score = 0u64;

for (val_idx, balance) in self.head_balance_source.unslashed_and_active_indices() {
let Some(vote) = votes.get(val_idx) else {
continue;
};
let vote_root = vote.current_root();
// Spec: get_latest_message_epoch(latest_messages[i]).
let vote_epoch = vote.current_slot().epoch(E::slots_per_epoch());

// vote_root.is_zero() == true means no latest message
if !vote_root.is_zero()
&& vote_epoch == target.epoch
&& !equivocating_indices.contains(&(val_idx as u64))
{
balance_by_vote_checkpoint.add(
(vote_root, vote_epoch),
self.head_balance_source.balance(val_idx),
)?;
balance_by_vote_checkpoint.add((vote_root, vote_epoch), balance)?;
}
}

// Spec: sum the effective balance of validators that:
// - Are active the current epoch
// - Are not slashed in the current epoch
// - Don't belong in the equivocating_indices set
// - Have a vote for the current target
let mut score = 0u64;

for ((vote_root, vote_epoch), balance) in balance_by_vote_checkpoint.iter() {
// Spec: get_checkpoint_for_block(store, latest_messages[i].root,
// get_latest_message_epoch(latest_messages[i])).
Expand Down
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