Merge pull request #1276

18f66f4 wallet: use the dynamic per kB fee (moneromooo-monero)
e6deb8a rpc: add a dynamic fee estimation RPC call (moneromooo-monero)
82dbba1 core: dynamic fee algorithm from ArticMine (moneromooo-monero)

src/cryptonote_config.h

@@ -64,6 +64,8 @@
 
 #define FEE_PER_KB_OLD                                  ((uint64_t)10000000000) // pow(10, 10)
 #define FEE_PER_KB                                      ((uint64_t)2000000000) // 2 * pow(10, 9)
+#define DYNAMIC_FEE_PER_KB_BASE_FEE                     ((uint64_t)2000000000) // 2 * pow(10,9)
+#define DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD            ((uint64_t)10000000000000) // 10 * pow(10,12)
 
 #define ORPHANED_BLOCKS_MAX_COUNT                       100
 
@@ -122,6 +124,8 @@
 
 #define THREAD_STACK_SIZE                       5 * 1024 * 1024
 
+#define HF_VERSION_DYNAMIC_FEE                  4
+
 // New constants are intended to go here
 namespace config
 {

src/cryptonote_core/blockchain.cpp

@@ -46,6 +46,7 @@
 #include "misc_language.h"
 #include "profile_tools.h"
 #include "file_io_utils.h"
+#include "common/int-util.h"
 #include "common/boost_serialization_helper.h"
 #include "warnings.h"
 #include "crypto/hash.h"
@@ -2708,6 +2709,87 @@ void Blockchain::check_ring_signature(const crypto::hash &tx_prefix_hash, const
   result = crypto::check_ring_signature(tx_prefix_hash, key_image, p_output_keys, sig.data()) ? 1 : 0;
 }
 
+//------------------------------------------------------------------
+uint64_t Blockchain::get_dynamic_per_kb_fee(uint64_t block_reward, size_t median_block_size)
+{
+  if (median_block_size < CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2)
+    median_block_size = CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2;
+
+  uint64_t unscaled_fee_per_kb = (DYNAMIC_FEE_PER_KB_BASE_FEE * CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / median_block_size);
+  uint64_t hi, lo = mul128(unscaled_fee_per_kb, block_reward, &hi);
+  static_assert(DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD % 1000000 == 0, "DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD must be divisible by 1000000");
+  static_assert(DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD / 1000000 <= std::numeric_limits<uint32_t>::max(), "DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD is too large");
+  // divide in two steps, since the divisor must be 32 bits, but DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD isn't
+  div128_32(hi, lo, DYNAMIC_FEE_PER_KB_BASE_BLOCK_REWARD / 1000000, &hi, &lo);
+  div128_32(hi, lo, 1000000, &hi, &lo);
+  assert(hi == 0);
+
+  return lo;
+}
+
+//------------------------------------------------------------------
+bool Blockchain::check_fee(size_t blob_size, uint64_t fee) const
+{
+  const uint8_t version = get_current_hard_fork_version();
+
+  uint64_t fee_per_kb;
+  if (version < HF_VERSION_DYNAMIC_FEE)
+  {
+    fee_per_kb = FEE_PER_KB;
+  }
+  else
+  {
+    uint64_t median = m_current_block_cumul_sz_limit / 2;
+    uint64_t already_generated_coins = m_db->height() ? m_db->get_block_already_generated_coins(m_db->height() - 1) : 0;
+    uint64_t base_reward;
+    if (!get_block_reward(median, 1, already_generated_coins, base_reward, version))
+      return false;
+    fee_per_kb = get_dynamic_per_kb_fee(base_reward, median);
+  }
+  LOG_PRINT_L2("Using " << print_money(fee) << "/kB fee");
+
+  uint64_t needed_fee = blob_size / 1024;
+  needed_fee += (blob_size % 1024) ? 1 : 0;
+  needed_fee *= fee_per_kb;
+
+  if (fee < needed_fee)
+  {
+    LOG_PRINT_L1("transaction fee is not enough: " << print_money(fee) << ", minimum fee: " << print_money(needed_fee));
+    return false;
+  }
+  return true;
+}
+
+//------------------------------------------------------------------
+uint64_t Blockchain::get_dynamic_per_kb_fee_estimate(uint64_t grace_blocks) const
+{
+  const uint8_t version = get_current_hard_fork_version();
+
+  if (version < HF_VERSION_DYNAMIC_FEE)
+    return FEE_PER_KB;
+
+  if (grace_blocks >= CRYPTONOTE_REWARD_BLOCKS_WINDOW)
+    grace_blocks = CRYPTONOTE_REWARD_BLOCKS_WINDOW - 1;
+
+  std::vector<size_t> sz;
+  get_last_n_blocks_sizes(sz, CRYPTONOTE_REWARD_BLOCKS_WINDOW - grace_blocks);
+  for (size_t i = 0; i < grace_blocks; ++i)
+    sz.push_back(CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2);
+
+  uint64_t median = epee::misc_utils::median(sz);
+  if(median <= CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2)
+    median = CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2;
+
+  uint64_t already_generated_coins = m_db->height() ? m_db->get_block_already_generated_coins(m_db->height() - 1) : 0;
+  uint64_t base_reward;
+  if (!get_block_reward(median, 1, already_generated_coins, base_reward, version))
+    return false;
+
+  uint64_t fee = get_dynamic_per_kb_fee(base_reward, median);
+  LOG_PRINT_L2("Estimating " << grace_blocks << "-block fee at " << print_money(fee) << "/kB");
+  return fee;
+}
+
 //------------------------------------------------------------------
 // This function checks to see if a tx is unlocked.  unlock_time is either
 // a block index or a unix time.

src/cryptonote_core/blockchain.h

@@ -512,6 +512,47 @@ namespace cryptonote
      */
     bool check_tx_inputs(transaction& tx, uint64_t& pmax_used_block_height, crypto::hash& max_used_block_id, tx_verification_context &tvc, bool kept_by_block = false);
 
+    /**
+     * @brief get dynamic per kB fee for a given block size
+     *
+     * The dynamic fee is based on the block size in a past window, and
+     * the current block reward. It is expressed by kB.
+     *
+     * @param block_reward the current block reward
+     * @param median_block_size the median blob's size in the past window
+     *
+     * @return the per kB fee
+     */
+    static uint64_t get_dynamic_per_kb_fee(uint64_t block_reward, size_t median_block_size);
+
+    /**
+     * @brief get dynamic per kB fee estimate for the next few blocks
+     *
+     * The dynamic fee is based on the block size in a past window, and
+     * the current block reward. It is expressed by kB. This function
+     * calculates an estimate for a dynamic fee which will be valid for
+     * the next grace_blocks
+     *
+     * @param grace_blocks number of blocks we want the fee to be valid for
+     *
+     * @return the per kB fee estimate
+     */
+    uint64_t get_dynamic_per_kb_fee_estimate(uint64_t grace_blocks) const;
+
+    /**
+     * @brief validate a transaction's fee
+     *
+     * This function validates the fee is enough for the transaction.
+     * This is based on the size of the transaction blob, and, after a
+     * height threshold, on the average size of transaction in a past window
+     *
+     * @param blob_size the transaction blob's size
+     * @param fee the fee
+     *
+     * @return true if the fee is enough, false otherwise
+     */
+    bool check_fee(size_t blob_size, uint64_t fee) const;
+
     /**
      * @brief check that a transaction's outputs conform to current standards
      *

src/cryptonote_core/tx_pool.cpp

@@ -133,12 +133,8 @@ namespace cryptonote
       fee = tx.rct_signatures.txnFee;
     }
 
-    uint64_t needed_fee = blob_size / 1024;
-    needed_fee += (blob_size % 1024) ? 1 : 0;
-    needed_fee *= FEE_PER_KB;
-    if (!kept_by_block && fee < needed_fee)
+    if (!kept_by_block && !m_blockchain.check_fee(blob_size, fee))
     {
-      LOG_PRINT_L1("transaction fee is not enough: " << print_money(fee) << ", minimum fee: " << print_money(needed_fee));
       tvc.m_verifivation_failed = true;
       tvc.m_fee_too_low = true;
       return false;

src/rpc/core_rpc_server.cpp

@@ -1283,6 +1283,13 @@ namespace cryptonote
     return true;
   }
   //------------------------------------------------------------------------------------------------------------------------------
+  bool core_rpc_server::on_get_per_kb_fee_estimate(const COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::request& req, COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::response& res, epee::json_rpc::error& error_resp)
+  {
+    res.fee = m_core.get_blockchain_storage().get_dynamic_per_kb_fee_estimate(req.grace_blocks);
+    res.status = CORE_RPC_STATUS_OK;
+    return true;
+  }
+  //------------------------------------------------------------------------------------------------------------------------------
   bool core_rpc_server::on_out_peers(const COMMAND_RPC_OUT_PEERS::request& req, COMMAND_RPC_OUT_PEERS::response& res)
   {
 	  // TODO

src/rpc/core_rpc_server.h

@@ -116,6 +116,7 @@ namespace cryptonote
         MAP_JON_RPC_WE("get_output_histogram",   on_get_output_histogram,       COMMAND_RPC_GET_OUTPUT_HISTOGRAM)
         MAP_JON_RPC_WE("get_version",            on_get_version,                COMMAND_RPC_GET_VERSION)
         MAP_JON_RPC_WE("get_coinbase_tx_sum",    on_get_coinbase_tx_sum,        COMMAND_RPC_GET_COINBASE_TX_SUM)
+        MAP_JON_RPC_WE("get_fee_estimate",       on_get_per_kb_fee_estimate,    COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE)
       END_JSON_RPC_MAP()
     END_URI_MAP2()
 
@@ -162,6 +163,7 @@ namespace cryptonote
     bool on_get_output_histogram(const COMMAND_RPC_GET_OUTPUT_HISTOGRAM::request& req, COMMAND_RPC_GET_OUTPUT_HISTOGRAM::response& res, epee::json_rpc::error& error_resp);
     bool on_get_version(const COMMAND_RPC_GET_VERSION::request& req, COMMAND_RPC_GET_VERSION::response& res, epee::json_rpc::error& error_resp);
     bool on_get_coinbase_tx_sum(const COMMAND_RPC_GET_COINBASE_TX_SUM::request& req, COMMAND_RPC_GET_COINBASE_TX_SUM::response& res, epee::json_rpc::error& error_resp);
+    bool on_get_per_kb_fee_estimate(const COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::request& req, COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::response& res, epee::json_rpc::error& error_resp);
     //-----------------------
 
 private:

src/rpc/core_rpc_server_commands_defs.h

@@ -1266,4 +1266,27 @@ namespace cryptonote
       END_KV_SERIALIZE_MAP()
     };
   };
+
+  struct COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE
+  {
+    struct request
+    {
+      uint64_t grace_blocks;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(grace_blocks)
+      END_KV_SERIALIZE_MAP()
+    };
+
+    struct response
+    {
+      std::string status;
+      uint64_t fee;
+
+      BEGIN_KV_SERIALIZE_MAP()
+        KV_SERIALIZE(status)
+        KV_SERIALIZE(fee)
+      END_KV_SERIALIZE_MAP()
+    };
+  };
 }

src/wallet/wallet2.cpp

@@ -80,6 +80,8 @@ using namespace cryptonote;
 #define RECENT_OUTPUT_RATIO (0.25) // 25% of outputs are from the recent zone
 #define RECENT_OUTPUT_ZONE (5 * 86400) // last 5 days are the recent zone
 
+#define FEE_ESTIMATE_GRACE_BLOCKS 10 // estimate fee valid for that many blocks
+
 #define KILL_IOSERVICE()  \
     do { \
       work.reset(); \
@@ -2765,6 +2767,40 @@ uint64_t wallet2::get_fee_multiplier(uint32_t priority, bool use_new_fee) const
   return 1;
 }
 //----------------------------------------------------------------------------------------------------
+uint64_t wallet2::get_dynamic_per_kb_fee_estimate()
+{
+  epee::json_rpc::request<cryptonote::COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::request> req_t = AUTO_VAL_INIT(req_t);
+  epee::json_rpc::response<cryptonote::COMMAND_RPC_GET_PER_KB_FEE_ESTIMATE::response, std::string> resp_t = AUTO_VAL_INIT(resp_t);
+
+  m_daemon_rpc_mutex.lock();
+  req_t.jsonrpc = "2.0";
+  req_t.id = epee::serialization::storage_entry(0);
+  req_t.method = "get_fee_estimate";
+  req_t.params.grace_blocks = FEE_ESTIMATE_GRACE_BLOCKS;
+  bool r = net_utils::invoke_http_json_remote_command2(m_daemon_address + "/json_rpc", req_t, resp_t, m_http_client);
+  m_daemon_rpc_mutex.unlock();
+  CHECK_AND_ASSERT_THROW_MES(r, "Failed to connect to daemon");
+  CHECK_AND_ASSERT_THROW_MES(resp_t.result.status != CORE_RPC_STATUS_BUSY, "Failed to connect to daemon");
+  CHECK_AND_ASSERT_THROW_MES(resp_t.result.status == CORE_RPC_STATUS_OK, "Failed to get fee estimate");
+  return resp_t.result.fee;
+}
+//----------------------------------------------------------------------------------------------------
+uint64_t wallet2::get_per_kb_fee()
+{
+  bool use_dyn_fee = use_fork_rules(HF_VERSION_DYNAMIC_FEE, -720 * 14);
+  if (!use_dyn_fee)
+    return FEE_PER_KB;
+  try
+  {
+    return get_dynamic_per_kb_fee_estimate();
+  }
+  catch (...)
+  {
+    LOG_PRINT_L1("Failed to query per kB fee, using " << print_money(FEE_PER_KB));
+    return FEE_PER_KB;
+  }
+}
+//----------------------------------------------------------------------------------------------------
 // separated the call(s) to wallet2::transfer into their own function
 //
 // this function will make multiple calls to wallet2::transfer if multiple
@@ -2774,7 +2810,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions(std::vector<crypto
   const std::vector<size_t> unused_transfers_indices = select_available_outputs_from_histogram(fake_outs_count + 1, true, true, trusted_daemon);
 
   const bool use_new_fee  = use_fork_rules(3, -720 * 14);
-  const uint64_t fee_per_kb  = use_new_fee ? FEE_PER_KB : FEE_PER_KB_OLD;
+  const uint64_t fee_per_kb  = get_per_kb_fee();
   const uint64_t fee_multiplier = get_fee_multiplier(priority, use_new_fee);
 
   // failsafe split attempt counter
@@ -3495,7 +3531,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_2(std::vector<cryp
   const bool use_rct = use_fork_rules(4, 0);
 
   const bool use_new_fee  = use_fork_rules(3, -720 * 14);
-  const uint64_t fee_per_kb  = use_new_fee ? FEE_PER_KB : FEE_PER_KB_OLD;
+  const uint64_t fee_per_kb  = get_per_kb_fee();
   const uint64_t fee_multiplier = get_fee_multiplier(priority, use_new_fee);
 
   // throw if attempting a transaction with no destinations
@@ -3777,7 +3813,7 @@ std::vector<wallet2::pending_tx> wallet2::create_transactions_from(const crypton
 
   const bool use_rct = fake_outs_count > 0 && use_fork_rules(4, 0);
   const bool use_new_fee  = use_fork_rules(3, -720 * 14);
-  const uint64_t fee_per_kb  = use_new_fee ? FEE_PER_KB : FEE_PER_KB_OLD;
+  const uint64_t fee_per_kb  = get_per_kb_fee();
   const uint64_t fee_multiplier = get_fee_multiplier(priority, use_new_fee);
 
   LOG_PRINT_L2("Starting with " << unused_transfers_indices.size() << " non-dust outputs and " << unused_dust_indices.size() << " dust outputs");
@@ -4083,7 +4119,7 @@ std::vector<wallet2::pending_tx> wallet2::create_unmixable_sweep_transactions(bo
   tx_dust_policy dust_policy(hf1_rules ? 0 : ::config::DEFAULT_DUST_THRESHOLD);
 
   const bool use_new_fee  = use_fork_rules(3, -720 * 14);
-  const uint64_t fee_per_kb  = use_new_fee ? FEE_PER_KB : FEE_PER_KB_OLD;
+  const uint64_t fee_per_kb  = get_per_kb_fee();
 
   // may throw
   std::vector<size_t> unmixable_outputs = select_available_unmixable_outputs(trusted_daemon);

src/wallet/wallet2.h

@@ -520,6 +520,8 @@ namespace tools
     uint64_t get_upper_tranaction_size_limit();
     std::vector<uint64_t> get_unspent_amounts_vector();
     uint64_t get_fee_multiplier(uint32_t priority, bool use_new_fee) const;
+    uint64_t get_dynamic_per_kb_fee_estimate();
+    uint64_t get_per_kb_fee();
     float get_output_relatedness(const transfer_details &td0, const transfer_details &td1) const;
     std::vector<size_t> pick_prefered_rct_inputs(uint64_t needed_money) const;
     void set_spent(size_t idx, uint64_t height);

tests/unit_tests/CMakeLists.txt

@@ -39,6 +39,7 @@ set(unit_tests_sources
   dns_resolver.cpp
   epee_boosted_tcp_server.cpp
   epee_levin_protocol_handler_async.cpp
+  fee.cpp
   get_xtype_from_string.cpp
   main.cpp
   mnemonics.cpp

tests/unit_tests/fee.cpp

@@ -0,0 +1,121 @@
+// Copyright (c) 2014-2016, 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.
+// 
+// Parts of this file are originally copyright (c) 2012-2013 The Cryptonote developers
+
+#include "gtest/gtest.h"
+
+#include "cryptonote_core/blockchain.h"
+
+using namespace cryptonote;
+
+namespace
+{
+  //--------------------------------------------------------------------------------------------------------------------
+  class fee : public ::testing::Test
+  {
+  };
+
+  TEST_F(fee, 10xmr)
+  {
+    // CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 and lower are clamped
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2), 2000000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 2), 2000000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 100), 2000000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, 1), 2000000000);
+
+    // higher is inverse proportional
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 2), 2000000000 / 2);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 10), 2000000000 / 10);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000), 2000000000 / 1000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(10000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000000ull), 2000000000 / 1000000);
+  }
+
+  TEST_F(fee, 1xmr)
+  {
+    // CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 and lower are clamped
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2), 200000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 2), 200000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 100), 200000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, 1), 200000000);
+
+    // higher is inverse proportional
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 2), 200000000 / 2);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 10), 200000000 / 10);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000), 200000000 / 1000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(1000000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000000ull), 200000000 / 1000000);
+  }
+
+  TEST_F(fee, dot3xmr)
+  {
+    // CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 and lower are clamped
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2), 60000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 2), 60000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 / 100), 60000000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, 1), 60000000);
+
+    // higher is inverse proportional
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 2), 60000000 / 2);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 10), 60000000 / 10);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000), 60000000 / 1000);
+    ASSERT_EQ(Blockchain::get_dynamic_per_kb_fee(300000000000, CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000000ull), 60000000 / 1000000);
+  }
+
+  static bool is_more_or_less(double x, double y)
+  {
+    return fabs(y - x) < 0.001;
+  }
+
+  static const double MAX_MULTIPLIER = 166.f;
+
+  TEST_F(fee, double_at_full)
+  {
+    static const uint64_t block_rewards[] = {
+      20000000000000ull, // 20 monero
+      13000000000000ull,
+      1000000000000ull,
+      600000000000ull, // .6 monero, minimum reward per block at 2min
+      300000000000ull, // .3 monero, minimum reward per block at 1min
+    };
+    static const uint64_t median_block_sizes[] = {
+      CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2,
+      CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 2,
+      CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 10,
+      CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000,
+      CRYPTONOTE_BLOCK_GRANTED_FULL_REWARD_ZONE_V2 * 1000000ull
+    };
+
+    for (uint64_t block_reward: block_rewards)
+    {
+      for (uint64_t median_block_size: median_block_sizes)
+      {
+        ASSERT_TRUE(is_more_or_less(Blockchain::get_dynamic_per_kb_fee(block_reward, median_block_size) * (median_block_size / 1024.) * MAX_MULTIPLIER / (double)block_reward, 1.992 * 1000 / 1024));
+      }
+    }
+  }
+}