Update to spec v1.7.0-alpha.4

consensus/state_processing/src/per_epoch_processing/altair.rs

@@ -51,8 +51,8 @@ pub fn process_epoch<E: EthSpec>(
     // without loss of correctness.
     let current_epoch_progressive_balances = state.progressive_balances_cache().clone();
     let current_epoch_total_active_balance = state.get_total_active_balance()?;
-    let participation_summary =
-        process_epoch_single_pass(state, spec, SinglePassConfig::default())?;
+    let epoch_result = process_epoch_single_pass(state, spec, SinglePassConfig::default())?;
+    let participation_summary = epoch_result.summary;
 
     // Reset eth1 data votes.
     process_eth1_data_reset(state)?;
@@ -79,6 +79,13 @@ pub fn process_epoch<E: EthSpec>(
 
     // Rotate the epoch caches to suit the epoch transition.
     state.advance_caches()?;
+
+    // Install the lookahead committee cache (built during PTC window processing) as the Next
+    // cache. After advance_caches, the lookahead epoch becomes the Next relative epoch.
+    if let Some(cache) = epoch_result.lookahead_committee_cache {
+        state.set_committee_cache(RelativeEpoch::Next, cache)?;
+    }
+
     update_progressive_balances_on_epoch_transition(state, spec)?;
 
     Ok(EpochProcessingSummary::Altair {

consensus/state_processing/src/per_epoch_processing/single_pass.rs

@@ -12,12 +12,13 @@ use milhouse::{Cow, List, Vector};
 use safe_arith::{SafeArith, SafeArithIter};
 use std::cmp::{max, min};
 use std::collections::{BTreeSet, HashMap};
+use std::sync::Arc;
 use tracing::instrument;
 use typenum::Unsigned;
 use types::{
     ActivationQueue, BeaconState, BeaconStateError, BuilderPendingPayment, ChainSpec, Checkpoint,
-    DepositData, Epoch, EthSpec, ExitCache, ForkName, ParticipationFlags, PendingDeposit,
-    ProgressiveBalancesCache, RelativeEpoch, Validator,
+    CommitteeCache, DepositData, Epoch, EthSpec, ExitCache, ForkName, ParticipationFlags,
+    PendingDeposit, ProgressiveBalancesCache, RelativeEpoch, Validator,
     consts::altair::{
         NUM_FLAG_INDICES, PARTICIPATION_FLAG_WEIGHTS, TIMELY_HEAD_FLAG_INDEX,
         TIMELY_TARGET_FLAG_INDEX, WEIGHT_DENOMINATOR,
@@ -34,6 +35,7 @@ pub struct SinglePassConfig {
     pub effective_balance_updates: bool,
     pub proposer_lookahead: bool,
     pub builder_pending_payments: bool,
+    pub ptc_window: bool,
 }
 
 impl Default for SinglePassConfig {
@@ -54,6 +56,7 @@ impl SinglePassConfig {
             effective_balance_updates: true,
             proposer_lookahead: true,
             builder_pending_payments: true,
+            ptc_window: true,
         }
     }
 
@@ -68,6 +71,7 @@ impl SinglePassConfig {
             effective_balance_updates: false,
             proposer_lookahead: false,
             builder_pending_payments: false,
+            ptc_window: false,
         }
     }
 }
@@ -139,12 +143,20 @@ impl ValidatorInfo {
     }
 }
 
+/// Result of single-pass epoch processing.
+pub struct SinglePassEpochResult<E: EthSpec> {
+    pub summary: ParticipationEpochSummary<E>,
+    /// Committee cache for the lookahead epoch, built during PTC window processing.
+    /// Can be installed as the Next committee cache after `advance_caches`.
+    pub lookahead_committee_cache: Option<Arc<CommitteeCache>>,
+}
+
 #[instrument(skip_all)]
 pub fn process_epoch_single_pass<E: EthSpec>(
     state: &mut BeaconState<E>,
     spec: &ChainSpec,
     conf: SinglePassConfig,
-) -> Result<ParticipationEpochSummary<E>, Error> {
+) -> Result<SinglePassEpochResult<E>, Error> {
     initialize_epoch_cache(state, spec)?;
     initialize_progressive_balances_cache(state, spec)?;
     state.build_exit_cache(spec)?;
@@ -479,7 +491,16 @@ pub fn process_epoch_single_pass<E: EthSpec>(
         process_proposer_lookahead(state, spec)?;
     }
 
-    Ok(summary)
+    let lookahead_committee_cache = if conf.ptc_window && fork_name.gloas_enabled() {
+        Some(process_ptc_window(state, spec)?)
+    } else {
+        None
+    };
+
+    Ok(SinglePassEpochResult {
+        summary,
+        lookahead_committee_cache,
+    })
 }
 
 // TOOO(EIP-7917): use balances cache
@@ -512,6 +533,53 @@ pub fn process_proposer_lookahead<E: EthSpec>(
     Ok(())
 }
 
+/// Process the PTC window, returning the committee cache built for the lookahead epoch.
+///
+/// The returned cache can be injected into the state's Next committee cache slot after
+/// `advance_caches` is called during the epoch transition, avoiding redundant recomputation.
+pub fn process_ptc_window<E: EthSpec>(
+    state: &mut BeaconState<E>,
+    spec: &ChainSpec,
+) -> Result<Arc<CommitteeCache>, Error> {
+    let slots_per_epoch = E::slots_per_epoch() as usize;
+
+    // Convert Vector -> List to use tree-efficient pop_front.
+    let ptc_window = state.ptc_window()?.clone();
+    let mut window: List<_, E::PtcWindowLength> = List::from(ptc_window);
+
+    // Drop the oldest epoch from the front (reuses shared tree nodes).
+    window
+        .pop_front(slots_per_epoch)
+        .map_err(|e| Error::BeaconStateError(BeaconStateError::MilhouseError(e)))?;
+
+    // Compute PTC for the new lookahead epoch
+    let next_epoch = state
+        .current_epoch()
+        .safe_add(spec.min_seed_lookahead.as_u64())?
+        .safe_add(1)?;
+    let start_slot = next_epoch.start_slot(E::slots_per_epoch());
+
+    // Build a committee cache for the lookahead epoch (beyond the normal Next bound)
+    let committee_cache = state.initialize_committee_cache_for_lookahead(next_epoch, spec)?;
+
+    for i in 0..slots_per_epoch {
+        let slot = start_slot.safe_add(i as u64)?;
+        let ptc = state.compute_ptc_with_cache(slot, &committee_cache, spec)?;
+        let ptc_u64: Vec<u64> = ptc.into_iter().map(|v| v as u64).collect();
+        let entry = ssz_types::FixedVector::new(ptc_u64)
+            .map_err(|e| Error::BeaconStateError(BeaconStateError::SszTypesError(e)))?;
+        window
+            .push(entry)
+            .map_err(|e| Error::BeaconStateError(BeaconStateError::MilhouseError(e)))?;
+    }
+
+    // Convert List back to Vector.
+    *state.ptc_window_mut()? = Vector::try_from(window)
+        .map_err(|e| Error::BeaconStateError(BeaconStateError::MilhouseError(e)))?;
+
+    Ok(committee_cache)
+}
+
 /// Calculate the quorum threshold for builder payments based on total active balance.
 fn get_builder_payment_quorum_threshold<E: EthSpec>(
     state_ctxt: &StateContext,

consensus/state_processing/src/upgrade/gloas.rs

@@ -2,7 +2,9 @@ use crate::per_block_processing::{
     is_valid_deposit_signature, process_operations::apply_deposit_for_builder,
 };
 use milhouse::{List, Vector};
+use safe_arith::SafeArith;
 use ssz_types::BitVector;
+use ssz_types::FixedVector;
 use std::collections::HashSet;
 use std::mem;
 use typenum::Unsigned;
@@ -102,13 +104,11 @@ pub fn upgrade_state_to_gloas<E: EthSpec>(
             vec![0xFFu8; E::SlotsPerHistoricalRoot::to_usize() / 8].into(),
         )
         .map_err(|_| Error::InvalidBitfield)?,
-        builder_pending_payments: Vector::new(vec![
-            BuilderPendingPayment::default();
-            E::builder_pending_payments_limit()
-        ])?,
+        builder_pending_payments: Vector::from_elem(BuilderPendingPayment::default())?,
         builder_pending_withdrawals: List::default(), // Empty list initially,
         latest_block_hash: pre.latest_execution_payload_header.block_hash,
         payload_expected_withdrawals: List::default(),
+        ptc_window: Vector::from_elem(FixedVector::from_elem(0))?, // placeholder, will be initialized below
         // Caches
         total_active_balance: pre.total_active_balance,
         progressive_balances_cache: mem::take(&mut pre.progressive_balances_cache),
@@ -120,10 +120,45 @@ pub fn upgrade_state_to_gloas<E: EthSpec>(
     });
     // [New in Gloas:EIP7732]
     onboard_builders_from_pending_deposits(&mut post, spec)?;
+    initialize_ptc_window(&mut post, spec)?;
 
     Ok(post)
 }
 
+/// Initialize the `ptc_window` field in the beacon state at fork transition.
+///
+/// The window contains:
+/// - One epoch of empty entries (previous epoch)
+/// - Computed PTC for the current epoch through `1 + MIN_SEED_LOOKAHEAD` epochs
+fn initialize_ptc_window<E: EthSpec>(
+    state: &mut BeaconState<E>,
+    spec: &ChainSpec,
+) -> Result<(), Error> {
+    let slots_per_epoch = E::slots_per_epoch() as usize;
+
+    let empty_previous_epoch = vec![FixedVector::<u64, E::PTCSize>::from_elem(0); slots_per_epoch];
+    let mut ptcs = empty_previous_epoch;
+
+    // Compute PTC for current epoch + lookahead epochs
+    let current_epoch = state.current_epoch();
+    for e in 0..=spec.min_seed_lookahead.as_u64() {
+        let epoch = current_epoch.safe_add(e)?;
+        let committee_cache = state.initialize_committee_cache_for_lookahead(epoch, spec)?;
+        let start_slot = epoch.start_slot(E::slots_per_epoch());
+        for i in 0..slots_per_epoch {
+            let slot = start_slot.safe_add(i as u64)?;
+            let ptc = state.compute_ptc_with_cache(slot, &committee_cache, spec)?;
+            let ptc_u64: Vec<u64> = ptc.into_iter().map(|v| v as u64).collect();
+            let entry = FixedVector::new(ptc_u64)?;
+            ptcs.push(entry);
+        }
+    }
+
+    *state.ptc_window_mut()? = Vector::new(ptcs)?;
+
+    Ok(())
+}
+
 /// Applies any pending deposit for builders, effectively onboarding builders at the fork.
 fn onboard_builders_from_pending_deposits<E: EthSpec>(
     state: &mut BeaconState<E>,

consensus/types/src/core/eth_spec.rs

@@ -6,9 +6,9 @@ use std::{
 use safe_arith::{ArithError, SafeArith};
 use serde::{Deserialize, Serialize};
 use typenum::{
-    U0, U1, U2, U4, U8, U16, U17, U32, U64, U128, U256, U512, U625, U1024, U2048, U4096, U8192,
-    U16384, U65536, U131072, U262144, U1048576, U16777216, U33554432, U134217728, U1073741824,
-    U1099511627776, UInt, Unsigned, bit::B0,
+    U0, U1, U2, U4, U8, U16, U17, U24, U32, U48, U64, U96, U128, U256, U512, U625, U1024, U2048,
+    U4096, U8192, U16384, U65536, U131072, U262144, U1048576, U16777216, U33554432, U134217728,
+    U1073741824, U1099511627776, UInt, Unsigned, bit::B0,
 };
 
 use crate::core::{ChainSpec, Epoch};
@@ -176,6 +176,7 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
      * New in Gloas
      */
     type PTCSize: Unsigned + Clone + Sync + Send + Debug + PartialEq;
+    type PtcWindowLength: Unsigned + Clone + Sync + Send + Debug + PartialEq;
     type MaxPayloadAttestations: Unsigned + Clone + Sync + Send + Debug + PartialEq;
     type BuilderPendingPaymentsLimit: Unsigned + Clone + Sync + Send + Debug + PartialEq;
     type BuilderPendingWithdrawalsLimit: Unsigned + Clone + Sync + Send + Debug + PartialEq;
@@ -428,6 +429,11 @@ pub trait EthSpec: 'static + Default + Sync + Send + Clone + Debug + PartialEq +
         Self::PTCSize::to_usize()
     }
 
+    /// Returns the `PtcWindowLength` constant for this specification.
+    fn ptc_window_length() -> usize {
+        Self::PtcWindowLength::to_usize()
+    }
+
     /// Returns the `MaxPayloadAttestations` constant for this specification.
     fn max_payload_attestations() -> usize {
         Self::MaxPayloadAttestations::to_usize()
@@ -515,6 +521,7 @@ impl EthSpec for MainnetEthSpec {
     type MaxWithdrawalRequestsPerPayload = U16;
     type MaxPendingDepositsPerEpoch = U16;
     type PTCSize = U512;
+    type PtcWindowLength = U96; // (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH
     type MaxPayloadAttestations = U4;
     type MaxBuildersPerWithdrawalsSweep = U16384;
 
@@ -561,6 +568,7 @@ impl EthSpec for MinimalEthSpec {
     type ProposerLookaheadSlots = U16; // Derived from (MIN_SEED_LOOKAHEAD + 1) * SLOTS_PER_EPOCH
     type BuilderPendingPaymentsLimit = U16; // 2 * SLOTS_PER_EPOCH = 2 * 8 = 16
     type PTCSize = U2;
+    type PtcWindowLength = U24; // (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH
     type MaxBuildersPerWithdrawalsSweep = U16;
 
     params_from_eth_spec!(MainnetEthSpec {
@@ -668,6 +676,7 @@ impl EthSpec for GnosisEthSpec {
     type ProposerLookaheadSlots = U32; // Derived from (MIN_SEED_LOOKAHEAD + 1) * SLOTS_PER_EPOCH
     type BuilderRegistryLimit = U1099511627776;
     type PTCSize = U512;
+    type PtcWindowLength = U48; // (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH
     type MaxPayloadAttestations = U2;
     type MaxBuildersPerWithdrawalsSweep = U16384;
 
@@ -694,6 +703,11 @@ mod test {
             E::proposer_lookahead_slots(),
             (spec.min_seed_lookahead.as_usize() + 1) * E::slots_per_epoch() as usize
         );
+        assert_eq!(
+            E::ptc_window_length(),
+            (spec.min_seed_lookahead.as_usize() + 2) * E::slots_per_epoch() as usize,
+            "PtcWindowLength must equal (2 + MIN_SEED_LOOKAHEAD) * SLOTS_PER_EPOCH"
+        );
     }
 
     #[test]