difficulty is fun

src/cryptonote_basic/difficulty.cpp

@@ -33,6 +33,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <vector>
+#include <boost/math/special_functions/round.hpp>
 
 #include "int-util.h"
 #include "crypto/hash.h"
@@ -121,10 +122,10 @@ namespace cryptonote {
 
   uint64_t next_difficulty_64(std::vector<std::uint64_t> timestamps, std::vector<uint64_t> cumulative_difficulties, size_t target_seconds) {
 
-    if(timestamps.size() > DIFFICULTY_WINDOW)
+    if(timestamps.size() > DIFFICULTY_WINDOW_V3)
     {
-      timestamps.resize(DIFFICULTY_WINDOW);
-      cumulative_difficulties.resize(DIFFICULTY_WINDOW);
+      timestamps.resize(DIFFICULTY_WINDOW_V3);
+      cumulative_difficulties.resize(DIFFICULTY_WINDOW_V3);
     }
 
 
@@ -133,17 +134,17 @@ namespace cryptonote {
     if (length <= 1) {
       return 1;
     }
-    static_assert(DIFFICULTY_WINDOW >= 2, "Window is too small");
-    assert(length <= DIFFICULTY_WINDOW);
+    static_assert(DIFFICULTY_WINDOW_V3 >= 2, "Window is too small");
+    assert(length <= DIFFICULTY_WINDOW_V3);
     sort(timestamps.begin(), timestamps.end());
     size_t cut_begin, cut_end;
-    static_assert(2 * DIFFICULTY_CUT <= DIFFICULTY_WINDOW - 2, "Cut length is too large");
-    if (length <= DIFFICULTY_WINDOW - 2 * DIFFICULTY_CUT) {
+    static_assert(2 * DIFFICULTY_CUT_V2 <= DIFFICULTY_WINDOW_V3 - 2, "Cut length is too large");
+    if (length <= DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2) {
       cut_begin = 0;
       cut_end = length;
     } else {
-      cut_begin = (length - (DIFFICULTY_WINDOW - 2 * DIFFICULTY_CUT) + 1) / 2;
-      cut_end = cut_begin + (DIFFICULTY_WINDOW - 2 * DIFFICULTY_CUT);
+      cut_begin = (length - (DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2) + 1) / 2;
+      cut_end = cut_begin + (DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2);
     }
     assert(/*cut_begin >= 0 &&*/ cut_begin + 2 <= cut_end && cut_end <= length);
     uint64_t time_span = timestamps[cut_end - 1] - timestamps[cut_begin];
@@ -200,7 +201,7 @@ namespace cryptonote {
       return check_hash_128(hash, difficulty);
   }
 
-  difficulty_type next_difficulty(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds) {
+  difficulty_type next_difficulty(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds, uint64_t HEIGHT) {
     //cutoff DIFFICULTY_LAG
     if(timestamps.size() > DIFFICULTY_WINDOW)
     {
@@ -214,6 +215,8 @@ namespace cryptonote {
     if (length <= 1) {
       return 1;
     }
+    // reset difficulty for solo mining to 100 million
+    if (HEIGHT <= 331170 + DIFFICULTY_WINDOW && HEIGHT >= 331170) { return 100000000; }
     static_assert(DIFFICULTY_WINDOW >= 2, "Window is too small");
     assert(length <= DIFFICULTY_WINDOW);
     sort(timestamps.begin(), timestamps.end());
@@ -254,4 +257,193 @@ namespace cryptonote {
     return "0x" + s;
   }
 
+  // LWMA difficulty algorithm
+  // Background:  https://github.com/zawy12/difficulty-algorithms/issues/3
+  // Copyright (c) 2017-2018 Zawy
+  difficulty_type next_difficulty_v2(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds, uint64_t HEIGHT) {
+    const int64_t T = static_cast<int64_t>(target_seconds);
+    size_t N = DIFFICULTY_WINDOW_V2;
+    if (timestamps.size() < 4) {
+        return 1;
+    } else if ( timestamps.size() < N+1 ) {
+        N = timestamps.size() - 1;
+    } else {
+        timestamps.resize(N+1);
+        cumulative_difficulties.resize(N+1);
+    }
+    const double adjust = 0.998;
+    const double k = N * (N + 1) / 2;
+    double LWMA(0), sum_inverse_D(0), harmonic_mean_D(0), nextDifficulty(0);
+    int64_t solveTime(0);
+    uint64_t difficulty(0), next_difficulty(0);
+    for (size_t i = 1; i <= N; i++) {
+      solveTime = static_cast<int64_t>(timestamps[i]) - static_cast<int64_t>(timestamps[i - 1]);
+      solveTime = std::min<int64_t>((T * 7), std::max<int64_t>(solveTime, (-7 * T)));
+      difficulty = static_cast<uint64_t>(cumulative_difficulties[i] - cumulative_difficulties[i - 1]);
+      LWMA += (int64_t)(solveTime * i) / k;
+      sum_inverse_D += 1 / static_cast<double>(difficulty);
+    }
+    harmonic_mean_D = N / sum_inverse_D;
+    if (static_cast<int64_t>(boost::math::round(LWMA)) < T / 20)
+      LWMA = static_cast<double>(T / 20);
+
+    nextDifficulty = harmonic_mean_D * T / LWMA * adjust;
+    next_difficulty = static_cast<uint64_t>(nextDifficulty);
+    return next_difficulty;
+  }
+
+  // LWMA-2
+  difficulty_type next_difficulty_v3(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT) {
+    int64_t T = DIFFICULTY_TARGET_V2;
+    int64_t N = DIFFICULTY_WINDOW_V2;
+    int64_t  L(0), ST, sum_3_ST(0), next_D, prev_D;
+    assert(timestamps.size() == cumulative_difficulties.size() && timestamps.size() <= static_cast<uint64_t>(N+1) );
+    for ( int64_t i = 1; i <= N; i++ ) {
+      ST = static_cast<int64_t>(timestamps[i]) - static_cast<int64_t>(timestamps[i-1]);
+      ST = std::max(-4*T, std::min(ST, 6*T));
+      L +=  ST * i ;
+      if ( i > N-3 ) {
+        sum_3_ST += ST;
+      }
+    }
+    next_D = (static_cast<int64_t>(cumulative_difficulties[N] - cumulative_difficulties[0])*T*(N+1)*99)/(100*2*L);
+    prev_D = static_cast<int64_t>(cumulative_difficulties[N] - cumulative_difficulties[N-1]);
+    next_D = std::max((prev_D*67)/100, std::min(next_D, (prev_D*150)/100));
+    if ( sum_3_ST < (8*T)/10) {
+      next_D = std::max(next_D,(prev_D*108)/100);
+    }
+    return static_cast<uint64_t>(next_D);
+  }
+
+  // LWMA-4
+  difficulty_type next_difficulty_v4(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT) {
+    uint64_t T = DIFFICULTY_TARGET_V2;
+    uint64_t N = DIFFICULTY_WINDOW_V2;
+    uint64_t L(0), ST(0), next_D, prev_D, avg_D, i;
+    assert(timestamps.size() == cumulative_difficulties.size() && timestamps.size() <= N+1 );
+    if (HEIGHT <= 63469 + 1) { return 100000069; }
+    std::vector<uint64_t>TS(N+1);
+    TS[0] = timestamps[0];
+    for ( i = 1; i <= N; i++) {
+      if ( timestamps[i]  > TS[i-1]  ) {   TS[i] = timestamps[i];  }
+      else {  TS[i] = TS[i-1];   }
+    }
+    for ( i = 1; i <= N; i++) {
+      if ( i > 4 && TS[i]-TS[i-1] > 5*T  && TS[i-1] - TS[i-4] < (14*T)/10 ) {   ST = 2*T; }
+      else if ( i > 7 && TS[i]-TS[i-1] > 5*T  && TS[i-1] - TS[i-7] < 4*T ) {   ST = 2*T; }
+      else {
+        ST = std::min(5*T ,TS[i] - TS[i-1]);
+      }
+      L +=  ST * i ;
+    }
+    if (L < N*N*T/20 ) { L =  N*N*T/20; }
+    avg_D = static_cast<uint64_t>(( cumulative_difficulties[N] - cumulative_difficulties[0] )/ N);
+    if (avg_D > 2000000*N*N*T) {
+      next_D = (avg_D/(200*L))*(N*(N+1)*T*97);
+    }
+    else {    next_D = (avg_D*N*(N+1)*T*97)/(200*L);    }
+    prev_D = static_cast<uint64_t>(cumulative_difficulties[N] - cumulative_difficulties[N-1]);
+    if (  ( TS[N] - TS[N-1] < (2*T)/10 ) ||
+         ( TS[N] - TS[N-2] < (5*T)/10 ) ||
+         ( TS[N] - TS[N-3] < (8*T)/10 )    )
+    {
+      next_D = std::max( next_D, std::min( (prev_D*110)/100, (105*avg_D)/100 ) );
+    }
+    i = 1000000000;
+    while (i > 1) {
+      if ( next_D > i*100 ) { next_D = ((next_D+i/2)/i)*i; break; }
+     else { i /= 10; }
+   }
+   if ( next_D > 100000 ) {
+    next_D = ((next_D+500)/1000)*1000 + std::min(static_cast<uint64_t>(999), (TS[N]-TS[N-10])/10);
+   }
+   return static_cast<uint64_t>(next_D);
+  }
+
+  // LWMA-1 difficulty algorithm
+  // Copyright (c) 2017-2019 Zawy, MIT License
+  // https://github.com/zawy12/difficulty-algorithms/issues/3
+  difficulty_type next_difficulty_v5(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT) {
+    uint64_t T = DIFFICULTY_TARGET_V2;
+    uint64_t N = DIFFICULTY_WINDOW_V3;
+    assert(timestamps.size() == cumulative_difficulties.size() && timestamps.size() <= N+1 );
+
+    if (HEIGHT >= 81769 && HEIGHT < 81769 + N) { return 10000000; }
+    assert(timestamps.size() == N+1);
+
+    // hardcoding previously erroneously calculated difficulty entries
+    if(HEIGHT == 307686) return 25800000;
+    if(HEIGHT == 307692) return 1890000;
+    if(HEIGHT == 307735) return 17900000;
+    if(HEIGHT == 307742) return 21300000;
+    if(HEIGHT == 307750) return 10900000;
+    if(HEIGHT == 307766) return 2960000;
+
+    uint64_t  i, this_timestamp(0), previous_timestamp(0);
+    difficulty_type L(0), next_D, avg_D;
+
+    previous_timestamp = timestamps[0]-T;
+    for ( i = 1; i <= N; i++) {
+    // Safely prevent out-of-sequence timestamps
+      if ( timestamps[i]  > previous_timestamp ) {   this_timestamp = timestamps[i];  }
+      else {  this_timestamp = previous_timestamp+1;   }
+      L +=  i*std::min(6*T ,this_timestamp - previous_timestamp);
+      previous_timestamp = this_timestamp;
+    }
+    if (L < N*N*T/20 ) { L =  N*N*T/20; }
+    avg_D = ( cumulative_difficulties[N] - cumulative_difficulties[0] )/ N;
+
+    // Prevent round off error for small D and overflow for large D.
+    if (avg_D > 2000000*N*N*T && HEIGHT < 307800) {
+      next_D = (avg_D/(200*L))*(N*(N+1)*T*99);
+    }
+    else if (avg_D > uint64_t(-1)/(N*(N+1)*T*99) && HEIGHT > 307800) {
+      next_D = (avg_D/(200*L))*(N*(N+1)*T*99);
+    }
+    else {    next_D = (avg_D*N*(N+1)*T*99)/(200*L);    }
+
+    // Make all insignificant digits zero for easy reading.
+    i = 1000000000;
+    while (i > 1) {
+      if ( next_D > i*100 ) { next_D = ((next_D+i/2)/i)*i; break; }
+      else { i /= 10; }
+    }
+    return  next_D;
+  }
+
+  difficulty_type next_difficulty_v6(std::vector<uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds) {
+    if(timestamps.size() > DIFFICULTY_WINDOW_V3)
+    {
+        timestamps.resize(DIFFICULTY_WINDOW_V3);
+        cumulative_difficulties.resize(DIFFICULTY_WINDOW_V3);
+    }
+    size_t length = timestamps.size();
+    assert(length == cumulative_difficulties.size());
+    if (length <= 1) {
+        return 1;
+    }
+    static_assert(DIFFICULTY_WINDOW_V3 >= 2, "Window is too small");
+    assert(length <= DIFFICULTY_WINDOW_V3);
+    sort(timestamps.begin(), timestamps.end());
+    size_t cut_begin, cut_end;
+    static_assert(2 * DIFFICULTY_CUT_V2 <= DIFFICULTY_WINDOW_V3 - 2, "Cut length is too large");
+    if (length <= DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2) {
+        cut_begin = 0;
+        cut_end = length;
+    } else {
+        cut_begin = (length - (DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2) + 1) / 2;
+        cut_end = cut_begin + (DIFFICULTY_WINDOW_V3 - 2 * DIFFICULTY_CUT_V2);
+    }
+    assert(/*cut_begin >= 0 &&*/ cut_begin + 2 <= cut_end && cut_end <= length);
+    uint64_t time_span = timestamps[cut_end - 1] - timestamps[cut_begin];
+    if (time_span == 0) {
+        time_span = 1;
+    }
+    difficulty_type total_work = cumulative_difficulties[cut_end - 1] - cumulative_difficulties[cut_begin];
+    assert(total_work > 0);
+    boost::multiprecision::uint256_t res =  (boost::multiprecision::uint256_t(total_work) * target_seconds + time_span - 1) / time_span;
+    if(res > max128bit)
+        return 0; // to behave like previous implementation, may be better return max128bit?
+    return res.convert_to<difficulty_type>();
+  }
 }

src/cryptonote_basic/difficulty.h

@@ -57,7 +57,12 @@ namespace cryptonote
 
     bool check_hash_128(const crypto::hash &hash, difficulty_type difficulty);
     bool check_hash(const crypto::hash &hash, difficulty_type difficulty);
-    difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
+    difficulty_type next_difficulty(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds, uint64_t HEIGHT);
+    difficulty_type next_difficulty_v2(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds, uint64_t HEIGHT);
+    difficulty_type next_difficulty_v3(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT);
+    difficulty_type next_difficulty_v4(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT);
+    difficulty_type next_difficulty_v5(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, uint64_t HEIGHT);
+    difficulty_type next_difficulty_v6(std::vector<std::uint64_t> timestamps, std::vector<difficulty_type> cumulative_difficulties, size_t target_seconds);
 
     std::string hex(difficulty_type v);
 }

src/cryptonote_config.h

@@ -84,8 +84,13 @@
 #define DIFFICULTY_WINDOW_V3                            144
 #define DIFFICULTY_WINDOW_V2                            60
 #define DIFFICULTY_WINDOW                               720 // blocks
+#define DIFFICULTY_LAG_V2                               3
 #define DIFFICULTY_LAG                                  15  // !!!
+#define DIFFICULTY_CUT_V2                               12
 #define DIFFICULTY_CUT                                  60  // timestamps to cut after sorting
+#define DIFFICULTY_BLOCKS_COUNT_V4                      DIFFICULTY_WINDOW_V3 + DIFFICULTY_LAG_V2
+#define DIFFICULTY_BLOCKS_COUNT_V3                      DIFFICULTY_WINDOW_V3 + 1
+#define DIFFICULTY_BLOCKS_COUNT_V2                      DIFFICULTY_WINDOW_V2 + 1
 #define DIFFICULTY_BLOCKS_COUNT                         DIFFICULTY_WINDOW + DIFFICULTY_LAG
 
 

src/cryptonote_core/blockchain.cpp

@@ -895,17 +895,19 @@ start:
   //    pop the oldest one from the list. This only requires 1x read per height instead
   //    of doing 735 (DIFFICULTY_BLOCKS_COUNT).
   bool check = false;
+  uint8_t version = get_current_hard_fork_version();
+  uint64_t difficulty_blocks_count = version >= 20 ? DIFFICULTY_BLOCKS_COUNT_V4 : version <= 17 && version >= 11 ? DIFFICULTY_BLOCKS_COUNT_V3 : version <= 10 && version >= 8 ? DIFFICULTY_BLOCKS_COUNT_V2 : DIFFICULTY_BLOCKS_COUNT;
   if (m_reset_timestamps_and_difficulties_height)
     m_timestamps_and_difficulties_height = 0;
-  if (m_timestamps_and_difficulties_height != 0 && ((height - m_timestamps_and_difficulties_height) == 1) && m_timestamps.size() >= DIFFICULTY_BLOCKS_COUNT)
+  if (m_timestamps_and_difficulties_height != 0 && ((height - m_timestamps_and_difficulties_height) == 1) && m_timestamps.size() >= difficulty_blocks_count)
   {
     uint64_t index = height - 1;
     m_timestamps.push_back(m_db->get_block_timestamp(index));
     m_difficulties.push_back(m_db->get_block_cumulative_difficulty(index));
 
-    while (m_timestamps.size() > DIFFICULTY_BLOCKS_COUNT)
+    while (m_timestamps.size() > difficulty_blocks_count)
       m_timestamps.erase(m_timestamps.begin());
-    while (m_difficulties.size() > DIFFICULTY_BLOCKS_COUNT)
+    while (m_difficulties.size() > difficulty_blocks_count)
       m_difficulties.erase(m_difficulties.begin());
 
     m_timestamps_and_difficulties_height = height;
@@ -918,7 +920,7 @@ start:
   std::vector<difficulty_type> difficulties_from_cache = difficulties;
 
   {
-    uint64_t offset = height - std::min <uint64_t> (height, static_cast<uint64_t>(DIFFICULTY_BLOCKS_COUNT));
+    uint64_t offset = height - std::min <uint64_t> (height, static_cast<uint64_t>(difficulty_blocks_count));
     if (offset == 0)
       ++offset;
 
@@ -964,7 +966,21 @@ start:
   }
 
   size_t target = get_difficulty_target();
-  difficulty_type diff = next_difficulty(timestamps, difficulties, target);
+  uint64_t HEIGHT = m_db->height();
+  difficulty_type diff;
+  if (version >= 20) {
+    diff = next_difficulty_v6(timestamps, difficulties, target);
+  } else if (version <= 17 && version >= 11) {
+    diff = next_difficulty_v5(timestamps, difficulties, HEIGHT);
+  } else if (version == 10) {
+    diff = next_difficulty_v4(timestamps, difficulties, HEIGHT);
+  } else if (version == 9) {
+    diff = next_difficulty_v3(timestamps, difficulties, HEIGHT);
+  } else if (version == 8) {
+    diff = next_difficulty_v2(timestamps, difficulties, target, HEIGHT);
+  } else {
+    diff = next_difficulty(timestamps, difficulties, target, HEIGHT);
+  }
 
   CRITICAL_REGION_LOCAL1(m_difficulty_lock);
   m_difficulty_for_next_block_top_hash = top_hash;
@@ -1023,11 +1039,13 @@ size_t Blockchain::recalculate_difficulties(boost::optional<uint64_t> start_heig
 
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> difficulties;
-  timestamps.reserve(DIFFICULTY_BLOCKS_COUNT + 1);
-  difficulties.reserve(DIFFICULTY_BLOCKS_COUNT + 1);
+  uint8_t version = get_current_hard_fork_version();
+  uint64_t difficulty_blocks_count = version >= 20 ? DIFFICULTY_BLOCKS_COUNT_V4 : version <= 17 && version >= 11 ? DIFFICULTY_BLOCKS_COUNT_V3 : version <= 10 && version >= 8 ? DIFFICULTY_BLOCKS_COUNT_V2 : DIFFICULTY_BLOCKS_COUNT;
+  timestamps.reserve(difficulty_blocks_count + 1);
+  difficulties.reserve(difficulty_blocks_count + 1);
   if (start_height > 1)
   {
-    for (uint64_t i = 0; i < DIFFICULTY_BLOCKS_COUNT; ++i)
+    for (uint64_t i = 0; i < difficulty_blocks_count; ++i)
     {
       uint64_t height = start_height - 1 - i;
       if (height == 0)
@@ -1042,7 +1060,21 @@ size_t Blockchain::recalculate_difficulties(boost::optional<uint64_t> start_heig
   for (uint64_t height = start_height; height <= top_height; ++height)
   {
     size_t target = get_ideal_hard_fork_version(height) < 2 ? DIFFICULTY_TARGET_V1 : DIFFICULTY_TARGET_V2;
-    difficulty_type recalculated_diff = next_difficulty(timestamps, difficulties, target);
+    uint64_t HEIGHT = m_db->height();
+    difficulty_type recalculated_diff;
+    if (version >= 20) {
+      recalculated_diff = next_difficulty_v6(timestamps, difficulties, target);
+    } else if (version <= 17 && version >= 11) {
+      recalculated_diff = next_difficulty_v5(timestamps, difficulties, HEIGHT);
+    } else if (version == 10) {
+      recalculated_diff = next_difficulty_v4(timestamps, difficulties, HEIGHT);
+    } else if (version == 9) {
+      recalculated_diff = next_difficulty_v3(timestamps, difficulties, HEIGHT);
+    } else if (version == 8) {
+      recalculated_diff = next_difficulty_v2(timestamps, difficulties, target, HEIGHT);
+    } else {
+      recalculated_diff = next_difficulty(timestamps, difficulties, target, HEIGHT);
+    }
 
     boost::multiprecision::uint256_t recalculated_cum_diff_256 = boost::multiprecision::uint256_t(recalculated_diff) + last_cum_diff;
     CHECK_AND_ASSERT_THROW_MES(recalculated_cum_diff_256 <= std::numeric_limits<difficulty_type>::max(), "Difficulty overflow!");
@@ -1070,9 +1102,9 @@ size_t Blockchain::recalculate_difficulties(boost::optional<uint64_t> start_heig
       timestamps.push_back(m_db->get_block_timestamp(height));
       difficulties.push_back(recalculated_cum_diff);
     }
-    if (timestamps.size() > DIFFICULTY_BLOCKS_COUNT)
+    if (timestamps.size() > difficulty_blocks_count)
     {
-      CHECK_AND_ASSERT_THROW_MES(timestamps.size() == DIFFICULTY_BLOCKS_COUNT + 1, "Wrong timestamps size: " << timestamps.size());
+      CHECK_AND_ASSERT_THROW_MES(timestamps.size() == difficulty_blocks_count + 1, "Wrong timestamps size: " << timestamps.size());
       timestamps.erase(timestamps.begin());
       difficulties.erase(difficulties.begin());
     }
@@ -1297,16 +1329,18 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   LOG_PRINT_L3("Blockchain::" << __func__);
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> cumulative_difficulties;
+  uint8_t version = get_current_hard_fork_version();
+  uint64_t difficulty_blocks_count = version >= 20 ? DIFFICULTY_BLOCKS_COUNT_V4 : version <= 17 && version >= 11 ? DIFFICULTY_BLOCKS_COUNT_V3 : version <= 10 && version >= 8 ? DIFFICULTY_BLOCKS_COUNT_V2 : DIFFICULTY_BLOCKS_COUNT;
 
   // if the alt chain isn't long enough to calculate the difficulty target
   // based on its blocks alone, need to get more blocks from the main chain
-  if(alt_chain.size()< DIFFICULTY_BLOCKS_COUNT)
+  if(alt_chain.size()< difficulty_blocks_count)
   {
     CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
     // Figure out start and stop offsets for main chain blocks
     size_t main_chain_stop_offset = alt_chain.size() ? alt_chain.front().height : bei.height;
-    size_t main_chain_count = DIFFICULTY_BLOCKS_COUNT - std::min(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT), alt_chain.size());
+    size_t main_chain_count = difficulty_blocks_count - std::min(static_cast<size_t>(difficulty_blocks_count), alt_chain.size());
     main_chain_count = std::min(main_chain_count, main_chain_stop_offset);
     size_t main_chain_start_offset = main_chain_stop_offset - main_chain_count;
 
@@ -1321,7 +1355,7 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
     }
 
     // make sure we haven't accidentally grabbed too many blocks...maybe don't need this check?
-    CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= DIFFICULTY_BLOCKS_COUNT, false, "Internal error, alt_chain.size()[" << alt_chain.size() << "] + vtimestampsec.size()[" << timestamps.size() << "] NOT <= DIFFICULTY_WINDOW[]" << DIFFICULTY_BLOCKS_COUNT);
+    CHECK_AND_ASSERT_MES((alt_chain.size() + timestamps.size()) <= difficulty_blocks_count, false, "Internal error, alt_chain.size()[" << alt_chain.size() << "] + vtimestampsec.size()[" << timestamps.size() << "] NOT <= DIFFICULTY_WINDOW[]" << difficulty_blocks_count);
 
     for (const auto &bei : alt_chain)
     {
@@ -1333,8 +1367,8 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   // and timestamps from it alone
   else
   {
-    timestamps.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
-    cumulative_difficulties.resize(static_cast<size_t>(DIFFICULTY_BLOCKS_COUNT));
+    timestamps.resize(static_cast<size_t>(difficulty_blocks_count));
+    cumulative_difficulties.resize(static_cast<size_t>(difficulty_blocks_count));
     size_t count = 0;
     size_t max_i = timestamps.size()-1;
     // get difficulties and timestamps from most recent blocks in alt chain
@@ -1343,7 +1377,7 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
       timestamps[max_i - count] = bei.bl.timestamp;
       cumulative_difficulties[max_i - count] = bei.cumulative_difficulty;
       count++;
-      if(count >= DIFFICULTY_BLOCKS_COUNT)
+      if(count >= difficulty_blocks_count)
         break;
     }
   }
@@ -1352,7 +1386,22 @@ difficulty_type Blockchain::get_next_difficulty_for_alternative_chain(const std:
   size_t target = get_ideal_hard_fork_version(bei.height) < 2 ? DIFFICULTY_TARGET_V1 : DIFFICULTY_TARGET_V2;
 
   // calculate the difficulty target for the block and return it
-  return next_difficulty(timestamps, cumulative_difficulties, target);
+  uint64_t HEIGHT = m_db->height();
+  difficulty_type next_diff;
+  if (version >= 20) {
+    next_diff = next_difficulty_v6(timestamps, cumulative_difficulties, target);
+  } else if (version <= 17 && version >= 11) {
+    next_diff = next_difficulty_v5(timestamps, cumulative_difficulties, HEIGHT);
+  } else if (version == 10) {
+    next_diff = next_difficulty_v4(timestamps, cumulative_difficulties, HEIGHT);
+  } else if (version == 9) {
+    next_diff = next_difficulty_v3(timestamps, cumulative_difficulties, HEIGHT);
+  } else if (version == 8) {
+    next_diff = next_difficulty_v2(timestamps, cumulative_difficulties, target, HEIGHT);
+  } else {
+    next_diff = next_difficulty(timestamps, cumulative_difficulties, target, HEIGHT);
+  }
+  return next_diff;
 }
 //------------------------------------------------------------------
 // This function does a sanity check on basic things that all miner