From 4b6c0198ad55de44884783c9914cb28d7d3d4fe1 Mon Sep 17 00:00:00 2001
From: Rob Walker <rob@solana.com>
Date: Wed, 10 Apr 2019 18:18:55 -0700
Subject: [PATCH] reset coding generator on slot boundaries (#3726)

---
 core/src/broadcast_stage.rs |  2 +-
 core/src/erasure.rs         | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/core/src/broadcast_stage.rs b/core/src/broadcast_stage.rs
index 543e4f483d..ea26a7e06e 100644
--- a/core/src/broadcast_stage.rs
+++ b/core/src/broadcast_stage.rs
@@ -53,7 +53,7 @@ impl Broadcast {
         let mut last_tick = entries.last().map(|v| v.1).unwrap_or(0);
         ventries.push(entries);
 
-        assert!(last_tick <= max_tick_height,);
+        assert!(last_tick <= max_tick_height);
         if last_tick != max_tick_height {
             while let Ok((same_bank, entries)) = receiver.try_recv() {
                 // If the bank changed, that implies the previous slot was interrupted and we do not have to
diff --git a/core/src/erasure.rs b/core/src/erasure.rs
index 97e0662bab..1b37038a80 100644
--- a/core/src/erasure.rs
+++ b/core/src/erasure.rs
@@ -297,6 +297,11 @@ impl CodingGenerator {
         let mut next_coding =
             Vec::with_capacity((self.leftover.len() + next_data.len()) / NUM_DATA * NUM_CODING);
 
+        if self.leftover.len() > 0 && next_data.len() > 0 {
+            if self.leftover[0].read().unwrap().slot() != next_data[0].read().unwrap().slot() {
+                self.leftover.clear(); // reset on slot boundaries
+            }
+        }
         let next_data: Vec<_> = self.leftover.iter().chain(next_data).cloned().collect();
 
         for data_blobs in next_data.chunks(NUM_DATA) {
@@ -641,6 +646,24 @@ pub mod test {
         }
     }
 
+    #[test]
+    fn test_erasure_generate_coding_reset_on_new_slot() {
+        solana_logger::setup();
+
+        let mut coding_generator = CodingGenerator::new();
+
+        // test coding by iterating one blob at a time
+        let data_blobs = generate_test_blobs(0, NUM_DATA * 2);
+
+        for i in NUM_DATA..NUM_DATA * 2 {
+            data_blobs[i].write().unwrap().set_slot(1);
+        }
+
+        let coding = coding_generator.next(&data_blobs[1..]).unwrap();
+
+        assert_eq!(coding.len(), NUM_CODING);
+    }
+
     #[test]
     fn test_generate_blocktree_with_coding() {
         let cases = vec![