From 4fccec158aaf2e63b779ddee268633d59f4e16c8 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Mon, 23 Sep 2019 22:22:19 +1000
Subject: [PATCH] Fix wasted iterations when getting previous state

---
 beacon_node/beacon_chain/src/beacon_chain.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/beacon_node/beacon_chain/src/beacon_chain.rs b/beacon_node/beacon_chain/src/beacon_chain.rs
index f0d1589643..731165f81f 100644
--- a/beacon_node/beacon_chain/src/beacon_chain.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain.rs
@@ -393,7 +393,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         } else {
             let state_root = self
                 .rev_iter_state_roots()
-                .find(|(_root, s)| *s == slot)
+                .take_while(|(_root, current_slot)| *current_slot >= slot)
+                .find(|(_root, current_slot)| *current_slot == slot)
                 .map(|(root, _slot)| root)
                 .ok_or_else(|| Error::NoStateForSlot(slot))?;