From 64dca6fba70b583ae189a3e17952c0d34be87eb2 Mon Sep 17 00:00:00 2001
From: Michael Sproul <michael@sigmaprime.io>
Date: Wed, 12 Jun 2019 15:40:48 +1000
Subject: [PATCH] committee cache: avoid spurious recomputes

Check that the committeee cache matches the absolute epoch for the relative epoch, rather than
always checking the previous epoch.
---
 eth2/types/src/beacon_state.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/eth2/types/src/beacon_state.rs b/eth2/types/src/beacon_state.rs
index c4000b8d8..b5dbf2a4a 100644
--- a/eth2/types/src/beacon_state.rs
+++ b/eth2/types/src/beacon_state.rs
@@ -110,7 +110,9 @@ where
     pub current_crosslinks: FixedLenVec<Crosslink, T::ShardCount>,
     pub previous_crosslinks: FixedLenVec<Crosslink, T::ShardCount>,
     pub latest_block_roots: FixedLenVec<Hash256, T::SlotsPerHistoricalRoot>,
+    #[compare_fields(as_slice)]
     latest_state_roots: FixedLenVec<Hash256, T::SlotsPerHistoricalRoot>,
+    #[compare_fields(as_slice)]
     latest_active_index_roots: FixedLenVec<Hash256, T::LatestActiveIndexRootsLength>,
     latest_slashed_balances: FixedLenVec<u64, T::LatestSlashedExitLength>,
     pub latest_block_header: BeaconBlockHeader,
@@ -795,7 +797,9 @@ impl<T: EthSpec> BeaconState<T> {
     ) -> Result<(), Error> {
         let i = Self::cache_index(relative_epoch);
 
-        if self.committee_caches[i].is_initialized_at(self.previous_epoch()) {
+        if self.committee_caches[i]
+            .is_initialized_at(relative_epoch.into_epoch(self.current_epoch()))
+        {
             Ok(())
         } else {
             self.force_build_committee_cache(relative_epoch, spec)