blockchain: keep a rolling long term block weight median

contrib/epee/include/rolling_median.h

@@ -0,0 +1,236 @@
+// Copyright (c) 2019, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+//
+// Adapted from source by AShelly:
+// Copyright (c) 2011 ashelly.myopenid.com, licenced under the MIT licence
+// https://stackoverflow.com/questions/5527437/rolling-median-in-c-turlach-implementation
+// https://stackoverflow.com/questions/1309263/rolling-median-algorithm-in-c
+// https://ideone.com/XPbl6
+
+#pragma once
+
+#include <stdlib.h>
+#include <stdint.h>
+
+namespace epee
+{
+namespace misc_utils
+{
+
+template<typename Item>
+struct rolling_median_t
+{
+private:
+  Item* data;  //circular queue of values
+  int*  pos;   //index into `heap` for each value
+  int*  heap;  //max/median/min heap holding indexes into `data`.
+  int   N;     //allocated size.
+  int   idx;   //position in circular queue
+  int   minCt; //count of items in min heap
+  int   maxCt; //count of items in max heap
+  int   sz;    //count of items in heap
+
+private:
+
+  //returns true if heap[i] < heap[j]
+  bool mmless(int i, int j) const
+  {
+    return data[heap[i]] < data[heap[j]];
+  }
+
+  //swaps items i&j in heap, maintains indexes
+  bool mmexchange(int i, int j)
+  {
+    const int t = heap[i];
+    heap[i] = heap[j];
+    heap[j] = t;
+    pos[heap[i]] = i;
+    pos[heap[j]] = j;
+    return 1;
+  }
+
+  //swaps items i&j if i<j;  returns true if swapped
+  bool mmCmpExch(int i, int j)
+  {
+     return mmless(i, j) && mmexchange(i, j);
+  }
+
+  //maintains minheap property for all items below i.
+  void minSortDown(int i)
+  {
+    for (i *= 2; i <= minCt; i *= 2)
+    {
+       if (i < minCt && mmless(i + 1, i))
+         ++i;
+       if (!mmCmpExch(i, i / 2))
+         break;
+    }
+  }
+
+  //maintains maxheap property for all items below i. (negative indexes)
+  void maxSortDown(int i)
+  {
+    for (i *= 2; i >= -maxCt; i *= 2)
+    {
+      if (i > -maxCt && mmless(i, i - 1))
+        --i;
+      if (!mmCmpExch(i / 2, i))
+        break;
+    }
+  }
+
+  //maintains minheap property for all items above i, including median
+  //returns true if median changed
+  bool minSortUp(int i)
+  {
+    while (i > 0 && mmCmpExch(i, i / 2))
+      i /= 2;
+    return i == 0;
+  }
+
+  //maintains maxheap property for all items above i, including median
+  //returns true if median changed
+  bool maxSortUp(int i)
+  {
+     while (i < 0 && mmCmpExch(i / 2, i))
+       i /= 2;
+     return i == 0;
+  }
+
+protected:
+  rolling_median_t &operator=(const rolling_median_t&) = delete;
+  rolling_median_t(const rolling_median_t&) = delete;
+
+public:
+  //creates new rolling_median_t: to calculate `nItems` running median. 
+  rolling_median_t(size_t N): N(N)
+  {
+    int size = N * (sizeof(Item) + sizeof(int) * 2);
+    data = (Item*)malloc(size);
+    pos = (int*) (data + N);
+    heap = pos + N + (N / 2); //points to middle of storage.
+    clear();
+  }
+
+  rolling_median_t(rolling_median_t &&m)
+  {
+    free(data);
+    memcpy(this, &m, sizeof(rolling_median_t));
+    m.data = NULL;
+  }
+  rolling_median_t &operator=(rolling_median_t &&m)
+  {
+    free(data);
+    memcpy(this, &m, sizeof(rolling_median_t));
+    m.data = NULL;
+    return *this;
+  }
+
+  ~rolling_median_t()
+  {
+    free(data);
+  }
+
+  void clear()
+  {
+    idx = 0;
+    minCt = 0;
+    maxCt = 0;
+    sz = 0;
+    int nItems = N;
+    while (nItems--)  //set up initial heap fill pattern: median,max,min,max,...
+    {
+      pos[nItems] = ((nItems + 1) / 2) * ((nItems & 1) ? -1 : 1);
+      heap[pos[nItems]] = nItems;
+    }
+  }
+
+  int size() const
+  {
+    return sz;
+  }
+
+  //Inserts item, maintains median in O(lg nItems)
+  void insert(Item v)
+  {
+    int p = pos[idx];
+    Item old = data[idx];
+    data[idx] = v;
+    idx = (idx + 1) % N;
+    sz = std::min<int>(sz + 1, N);
+    if (p > 0)         //new item is in minHeap
+    {
+      if (minCt < (N - 1) / 2)
+      {
+        ++minCt;
+      }
+      else if (v > old)
+      {
+        minSortDown(p);
+        return;
+      }
+      if (minSortUp(p) && mmCmpExch(0, -1))
+        maxSortDown(-1);
+    }
+    else if (p < 0)   //new item is in maxheap
+    {
+      if (maxCt < N / 2)
+      {
+        ++maxCt;
+      }
+      else if (v < old)
+      {
+        maxSortDown(p);
+        return;
+      }
+      if (maxSortUp(p) && minCt && mmCmpExch(1, 0))
+        minSortDown(1);
+    }
+    else //new item is at median
+    {
+      if (maxCt && maxSortUp(-1))
+        maxSortDown(-1);
+      if (minCt && minSortUp(1))
+        minSortDown(1);
+    }
+  }
+
+  //returns median item (or average of 2 when item count is even)
+  Item median() const
+  {
+    Item v = data[heap[0]];
+    if (minCt < maxCt)
+    {
+      v = (v + data[heap[-1]]) / 2;
+    }
+    return v;
+  }
+};
+
+}
+}

src/cryptonote_core/blockchain.cpp

@@ -179,6 +179,7 @@ Blockchain::Blockchain(tx_memory_pool& tx_pool) :
   m_long_term_block_weights_window(CRYPTONOTE_LONG_TERM_BLOCK_WEIGHT_WINDOW_SIZE),
   m_long_term_effective_median_block_weight(0),
   m_long_term_block_weights_cache_tip_hash(crypto::null_hash),
+  m_long_term_block_weights_cache_rolling_median(CRYPTONOTE_LONG_TERM_BLOCK_WEIGHT_WINDOW_SIZE),
   m_difficulty_for_next_block_top_hash(crypto::null_hash),
   m_difficulty_for_next_block(1),
   m_btc_valid(false)
@@ -519,7 +520,10 @@ bool Blockchain::init(BlockchainDB* db, const network_type nettype, bool offline
   }
 
   if (test_options && test_options->long_term_block_weight_window)
+  {
     m_long_term_block_weights_window = test_options->long_term_block_weight_window;
+    m_long_term_block_weights_cache_rolling_median = epee::misc_utils::rolling_median_t<uint64_t>(m_long_term_block_weights_window);
+  }
 
   {
     db_txn_guard txn_guard(m_db, m_db->is_read_only());
@@ -1283,21 +1287,20 @@ void Blockchain::get_last_n_blocks_weights(std::vector<uint64_t>& weights, size_
   weights = m_db->get_block_weights(start_offset, count);
 }
 //------------------------------------------------------------------
-void Blockchain::get_long_term_block_weights(std::vector<uint64_t>& weights, uint64_t start_height, size_t count) const
+uint64_t Blockchain::get_long_term_block_weight_median(uint64_t start_height, size_t count) const
 {
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
   PERF_TIMER(get_long_term_block_weights);
 
-  if (count == 0)
+  CHECK_AND_ASSERT_THROW_MES(count > 0, "count == 0");
-    return;
 
   bool cached = false;
   uint64_t blockchain_height = m_db->height();
   uint64_t tip_height = start_height + count - 1;
   crypto::hash tip_hash = crypto::null_hash;
-  if (tip_height < blockchain_height && count == m_long_term_block_weights_cache.size())
+  if (tip_height < blockchain_height && count == (size_t)m_long_term_block_weights_cache_rolling_median.size())
   {
     tip_hash = m_db->get_block_hash_from_height(tip_height);
     cached = tip_hash == m_long_term_block_weights_cache_tip_hash;
@@ -1306,32 +1309,30 @@ void Blockchain::get_long_term_block_weights(std::vector<uint64_t>& weights, uin
   if (cached)
   {
     MTRACE("requesting " << count << " from " << start_height << ", cached");
-    weights = m_long_term_block_weights_cache;
+    return m_long_term_block_weights_cache_rolling_median.median();
-    return;
   }
 
   // in the vast majority of uncached cases, most is still cached,
   // as we just move the window one block up:
-  if (tip_height > 0 && count == m_long_term_block_weights_cache.size() && tip_height < blockchain_height)
+  if (tip_height > 0 && count == (size_t)m_long_term_block_weights_cache_rolling_median.size() && tip_height < blockchain_height)
   {
     crypto::hash old_tip_hash = m_db->get_block_hash_from_height(tip_height - 1);
     if (old_tip_hash == m_long_term_block_weights_cache_tip_hash)
     {
-      weights = m_long_term_block_weights_cache;
-      for (size_t i = 1; i < weights.size(); ++i)
-        weights[i - 1] = weights[i];
       MTRACE("requesting " << count << " from " << start_height << ", incremental");
-      weights.back() = m_db->get_block_long_term_weight(tip_height);
-      m_long_term_block_weights_cache = weights;
       m_long_term_block_weights_cache_tip_hash = tip_hash;
-      return;
+      m_long_term_block_weights_cache_rolling_median.insert(m_db->get_block_long_term_weight(tip_height));
+      return m_long_term_block_weights_cache_rolling_median.median();
     }
   }
 
   MTRACE("requesting " << count << " from " << start_height << ", uncached");
-  weights = m_db->get_long_term_block_weights(start_height, count);
+  std::vector<uint64_t> weights = m_db->get_long_term_block_weights(start_height, count);
-  m_long_term_block_weights_cache = weights;
   m_long_term_block_weights_cache_tip_hash = tip_hash;
+  m_long_term_block_weights_cache_rolling_median.clear();
+  for (uint64_t w: weights)
+    m_long_term_block_weights_cache_rolling_median.insert(w);
+  return m_long_term_block_weights_cache_rolling_median.median();
 }
 //------------------------------------------------------------------
 uint64_t Blockchain::get_current_cumulative_block_weight_limit() const
@@ -3934,9 +3935,7 @@ uint64_t Blockchain::get_next_long_term_block_weight(uint64_t block_weight) cons
   if (hf_version < HF_VERSION_LONG_TERM_BLOCK_WEIGHT)
     return block_weight;
 
-  std::vector<uint64_t> weights;
+  uint64_t long_term_median = get_long_term_block_weight_median(db_height - nblocks, nblocks);
-  get_long_term_block_weights(weights, db_height - nblocks, nblocks);
-  uint64_t long_term_median = epee::misc_utils::median(weights);
   uint64_t 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 = long_term_effective_median_block_weight + long_term_effective_median_block_weight * 2 / 5;
@@ -3968,7 +3967,6 @@ bool Blockchain::update_next_cumulative_weight_limit(uint64_t *long_term_effecti
   {
     const uint64_t block_weight = m_db->get_block_weight(db_height - 1);
 
-    std::vector<uint64_t> weights, new_weights;
     uint64_t long_term_median;
     if (db_height == 1)
     {
@@ -3979,9 +3977,7 @@ bool Blockchain::update_next_cumulative_weight_limit(uint64_t *long_term_effecti
       uint64_t nblocks = std::min<uint64_t>(m_long_term_block_weights_window, db_height);
       if (nblocks == db_height)
         --nblocks;
-      get_long_term_block_weights(weights, db_height - nblocks - 1, nblocks);
+      long_term_median = get_long_term_block_weight_median(db_height - nblocks - 1, nblocks);
-      new_weights = weights;
-      long_term_median = epee::misc_utils::median(weights);
     }
 
     m_long_term_effective_median_block_weight = std::max<uint64_t>(CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V5, long_term_median);
@@ -3989,13 +3985,19 @@ bool Blockchain::update_next_cumulative_weight_limit(uint64_t *long_term_effecti
     uint64_t short_term_constraint = m_long_term_effective_median_block_weight + m_long_term_effective_median_block_weight * 2 / 5;
     long_term_block_weight = std::min<uint64_t>(block_weight, short_term_constraint);
 
-    if (new_weights.empty())
+    if (db_height == 1)
-      new_weights.resize(1);
+    {
-    new_weights[0] = long_term_block_weight;
+      long_term_median = long_term_block_weight;
-    long_term_median = epee::misc_utils::median(new_weights);
+    }
+    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);
 
-    weights.clear();
+    std::vector<uint64_t> weights;
     get_last_n_blocks_weights(weights, CRYPTONOTE_REWARD_BLOCKS_WINDOW);
 
     uint64_t short_term_median = epee::misc_utils::median(weights);

src/cryptonote_core/blockchain.h

@@ -37,7 +37,6 @@
 #include <boost/multi_index/global_fun.hpp>
 #include <boost/multi_index/hashed_index.hpp>
 #include <boost/multi_index/member.hpp>
-#include <boost/circular_buffer.hpp>
 #include <atomic>
 #include <functional>
 #include <unordered_map>
@@ -46,6 +45,7 @@
 #include "span.h"
 #include "syncobj.h"
 #include "string_tools.h"
+#include "rolling_median.h"
 #include "cryptonote_basic/cryptonote_basic.h"
 #include "common/util.h"
 #include "cryptonote_protocol/cryptonote_protocol_defs.h"
@@ -1064,7 +1064,7 @@ namespace cryptonote
     uint64_t m_long_term_block_weights_window;
     uint64_t m_long_term_effective_median_block_weight;
     mutable crypto::hash m_long_term_block_weights_cache_tip_hash;
-    mutable std::vector<uint64_t> m_long_term_block_weights_cache;
+    mutable epee::misc_utils::rolling_median_t<uint64_t> m_long_term_block_weights_cache_rolling_median;
 
     epee::critical_section m_difficulty_lock;
     crypto::hash m_difficulty_for_next_block_top_hash;
@@ -1314,15 +1314,16 @@ namespace cryptonote
     void get_last_n_blocks_weights(std::vector<uint64_t>& weights, size_t count) const;
 
     /**
-     * @brief gets recent block long term weights for median calculation
+     * @brief gets block long term weight median
      *
-     * get the block long term weights of the last <count> blocks, and return by reference <weights>.
+     * get the block long term weight median of <count> blocks starting at <start_height>
      *
-     * @param weights return-by-reference the list of weights
      * @param start_height the block height of the first block to query
      * @param count the number of blocks to get weights for
+     *
+     * @return the long term median block weight
      */
-    void get_long_term_block_weights(std::vector<uint64_t>& weights, uint64_t start_height, size_t count) const;
+    uint64_t get_long_term_block_weight_median(uint64_t start_height, size_t count) const;
 
     /**
      * @brief checks if a transaction is unlocked (its outputs spendable)

src/daemon/rpc_command_executor.cpp

@@ -722,7 +722,7 @@ bool t_rpc_command_executor::print_blockchain_info(uint64_t start_block_index, u
       tools::msg_writer() << "" << std::endl;
     tools::msg_writer()
       << "height: " << header.height << ", timestamp: " << header.timestamp << " (" << tools::get_human_readable_timestamp(header.timestamp) << ")"
-      << ", size: " << header.block_size << ", weight: " << header.block_weight << ", transactions: " << header.num_txes << std::endl
+      << ", size: " << header.block_size << ", weight: " << header.block_weight << " (long term " << header.long_term_weight << "), transactions: " << header.num_txes << std::endl
       << "major version: " << (unsigned)header.major_version << ", minor version: " << (unsigned)header.minor_version << std::endl
       << "block id: " << header.hash << ", previous block id: " << header.prev_hash << std::endl
       << "difficulty: " << header.difficulty << ", nonce " << header.nonce << ", reward " << cryptonote::print_money(header.reward) << std::endl;

tests/unit_tests/CMakeLists.txt

@@ -72,6 +72,7 @@ set(unit_tests_sources
   parse_amount.cpp
   pruning.cpp
   random.cpp
+  rolling_median.cpp
   serialization.cpp
   sha256.cpp
   slow_memmem.cpp

tests/unit_tests/rolling_median.cpp

@@ -0,0 +1,202 @@
+// Copyright (c) 2019, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <random>
+#include "gtest/gtest.h"
+#include "misc_language.h"
+#include "rolling_median.h"
+#include "crypto/crypto.h"
+
+TEST(rolling_median, one)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(1);
+  m.insert(42);
+  ASSERT_EQ(m.median(), 42);
+  m.insert(18);
+  ASSERT_EQ(m.median(), 18);
+  m.insert(7483);
+  ASSERT_EQ(m.median(), 7483);
+}
+
+TEST(rolling_median, two)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(2);
+  m.insert(42);
+  ASSERT_EQ(m.median(), 42);
+  m.insert(45);
+  ASSERT_EQ(m.median(), 43);
+  m.insert(49);
+  ASSERT_EQ(m.median(), 47);
+  m.insert(41);
+  ASSERT_EQ(m.median(), 45);
+  m.insert(43);
+  ASSERT_EQ(m.median(), 42);
+  m.insert(40);
+  ASSERT_EQ(m.median(), 41);
+  m.insert(41);
+  ASSERT_EQ(m.median(), 40);
+}
+
+TEST(rolling_median, series)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(100);
+  std::vector<uint64_t> v;
+  v.reserve(100);
+  for (int i = 0; i < 10000; ++i)
+  {
+    uint64_t r = rand();
+    v.push_back(r);
+    if (v.size() > 100)
+      v.erase(v.begin());
+    m.insert(r);
+    std::vector<uint64_t> vcopy = v;
+    ASSERT_EQ(m.median(), epee::misc_utils::median(vcopy));
+  }
+}
+
+TEST(rolling_median, clear_whole)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(100);
+  std::vector<uint64_t> random, median;
+  random.reserve(10000);
+  median.reserve(10000);
+  for (int i = 0; i < 10000; ++i)
+  {
+    random.push_back(rand());
+    m.insert(random.back());
+    median.push_back(m.median());
+  }
+  m.clear();
+  for (int i = 0; i < 10000; ++i)
+  {
+    m.insert(random[i]);
+    ASSERT_EQ(median[i], m.median());
+  }
+}
+
+TEST(rolling_median, clear_partway)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(100);
+  std::vector<uint64_t> random, median;
+  random.reserve(10000);
+  median.reserve(10000);
+  for (int i = 0; i < 10000; ++i)
+  {
+    random.push_back(rand());
+    m.insert(random.back());
+    median.push_back(m.median());
+  }
+  m.clear();
+  for (int i = 10000 - 100; i < 10000; ++i)
+  {
+    m.insert(random[i]);
+  }
+  ASSERT_EQ(median[10000-1], m.median());
+}
+
+TEST(rolling_median, order)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(1000);
+  std::vector<uint64_t> random;
+  random.reserve(1000);
+  for (int i = 0; i < 1000; ++i)
+  {
+    random.push_back(rand());
+    m.insert(random.back());
+  }
+  const uint64_t med = m.median();
+
+  std::sort(random.begin(), random.end(), [](uint64_t a, uint64_t b) { return a < b; });
+  m.clear();
+  for (int i = 0; i < 1000; ++i)
+    m.insert(random[i]);
+  ASSERT_EQ(med, m.median());
+
+  std::sort(random.begin(), random.end(), [](uint64_t a, uint64_t b) { return a > b; });
+  m.clear();
+  for (int i = 0; i < 1000; ++i)
+    m.insert(random[i]);
+  ASSERT_EQ(med, m.median());
+
+  std::shuffle(random.begin(), random.end(), std::default_random_engine(crypto::rand<unsigned>()));
+  m.clear();
+  for (int i = 0; i < 1000; ++i)
+    m.insert(random[i]);
+  ASSERT_EQ(med, m.median());
+}
+
+TEST(rolling_median, history_blind)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(10);
+
+  uint64_t median = 0;
+  for (int i = 0; i < 1000; ++i)
+  {
+    m.clear();
+    int history_length = 743723 % (i+1);
+    while (history_length--)
+      m.insert(743284 % (i+1));
+    for (int j = 0; j < 10; ++j)
+      m.insert(8924829384 % (j+1));
+    if (i == 0)
+      median = m.median();
+    else
+      ASSERT_EQ(median, m.median());
+  }
+}
+
+TEST(rolling_median, size)
+{
+  epee::misc_utils::rolling_median_t<uint64_t> m(10);
+
+  ASSERT_EQ(m.size(), 0);
+  m.insert(1);
+  ASSERT_EQ(m.size(), 1);
+  m.insert(2);
+  ASSERT_EQ(m.size(), 2);
+  m.clear();
+  ASSERT_EQ(m.size(), 0);
+  for (int i = 0; i < 10; ++i)
+  {
+    m.insert(80 % (i + 1));
+    ASSERT_EQ(m.size(), i + 1);
+  }
+  m.insert(1);
+  ASSERT_EQ(m.size(), 10);
+  m.insert(2);
+  ASSERT_EQ(m.size(), 10);
+  m.clear();
+  ASSERT_EQ(m.size(), 0);
+  m.insert(4);
+  ASSERT_EQ(m.size(), 1);
+  for (int i = 0; i < 1000; ++i)
+  {
+    m.insert(80 % (i + 1));
+    ASSERT_EQ(m.size(), std::min<int>(10, i + 2));
+  }
+}