Merge pull request monero-project#9013

bb33daa add a test for the long term weight cache (Boog900)
65839b5 Fix: long term block weight cache The long term block weight cache was doing a wrong calculation when adding a new block to the cache. (Boog900)

src/cryptonote_core/blockchain.cpp

@@ -4615,40 +4615,9 @@ bool Blockchain::update_next_cumulative_weight_limit(uint64_t *long_term_effecti
   }
   else
   {
-    const uint64_t block_weight = m_db->get_block_weight(db_height - 1);
+    const uint64_t nblocks = std::min<uint64_t>(m_long_term_block_weights_window, db_height);
+    const uint64_t long_term_median = get_long_term_block_weight_median(db_height - nblocks, nblocks);
 
-    uint64_t long_term_median;
-    if (db_height == 1)
-    {
-      long_term_median = CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V5;
-    }
-    else
-    {
-      uint64_t nblocks = std::min<uint64_t>(m_long_term_block_weights_window, db_height);
-      if (nblocks == db_height)
-        --nblocks;
-      long_term_median = get_long_term_block_weight_median(db_height - nblocks - 1, nblocks);
-    }
-
-    m_long_term_effective_median_block_weight = std::max<uint64_t>(CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V5, long_term_median);
-
-    uint64_t short_term_constraint = m_long_term_effective_median_block_weight;
-    if (hf_version >= HF_VERSION_2021_SCALING)
-      short_term_constraint += m_long_term_effective_median_block_weight * 7 / 10;
-    else
-      short_term_constraint += m_long_term_effective_median_block_weight * 2 / 5;
-    uint64_t long_term_block_weight = std::min<uint64_t>(block_weight, short_term_constraint);
-
-    if (db_height == 1)
-    {
-      long_term_median = long_term_block_weight;
-    }
-    else
-    {
-      m_long_term_block_weights_cache_tip_hash = m_db->get_block_hash_from_height(db_height - 1);
-      m_long_term_block_weights_cache_rolling_median.insert(long_term_block_weight);
-      long_term_median = m_long_term_block_weights_cache_rolling_median.median();
-    }
     m_long_term_effective_median_block_weight = std::max<uint64_t>(CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V5, long_term_median);
 
     std::vector<uint64_t> weights;

tests/unit_tests/long_term_block_weight.cpp

@@ -400,3 +400,38 @@ TEST(long_term_block_weight, long_growth_spike_and_drop)
   ASSERT_GT(long_term_effective_median_block_weight, 300000 * 1.07);
   ASSERT_LT(long_term_effective_median_block_weight, 300000 * 1.09);
 }
+
+TEST(long_term_block_weight, cache_matches_true_value)
+{
+  PREFIX(16);
+
+  // Add big blocks to increase the block weight limit 
+  for (uint64_t h = 0; h <= 2000; ++h)
+  {
+    size_t w = bc->get_current_cumulative_block_weight_limit();
+    uint64_t ltw = bc->get_next_long_term_block_weight(w);
+    bc->get_db().add_block(std::make_pair(cryptonote::block(), ""), w, ltw, h, h, {});
+    bc->update_next_cumulative_weight_limit();
+  }
+
+  ASSERT_GT(bc->get_current_cumulative_block_weight_limit() * 10/17 , 300000);
+
+  // Add small blocks to the top of the chain
+  for (uint64_t h = 2000; h <= 5001; ++h)
+  {
+    size_t w = (bc->get_current_cumulative_block_weight_median() * 10/17) - 1000;
+    uint64_t ltw = bc->get_next_long_term_block_weight(w);
+    bc->get_db().add_block(std::make_pair(cryptonote::block(), ""), w, ltw, h, h, {});
+    bc->update_next_cumulative_weight_limit();
+  }
+
+  // get the weight limit
+  uint64_t weight_limit = bc->get_current_cumulative_block_weight_limit();
+  // refresh the cache
+  bc->m_long_term_block_weights_cache_rolling_median.clear();
+  bc->get_long_term_block_weight_median(bc->get_db().height() - TEST_LONG_TERM_BLOCK_WEIGHT_WINDOW, TEST_LONG_TERM_BLOCK_WEIGHT_WINDOW);
+  bc->update_next_cumulative_weight_limit();
+
+  // make sure the weight limit is the same
+  ASSERT_EQ(weight_limit, bc->get_current_cumulative_block_weight_limit());
+}