Use floating point in payment calculations

contracts/eosio.system/common.hpp

@@ -53,20 +53,4 @@ namespace eosiosystem {
          }
    };
 
-   std::pair<uint64_t, uint64_t> int_logarithm_one_plus(uint32_t x) {
-      static const uint64_t denom = 10000;
-      uint64_t ret = 0;
-      uint64_t x_power = x;
-      const uint64_t n = 4;
-      static const uint64_t ten_power = denom * denom * denom * denom;
-      for (uint64_t i = 0, p = ten_power; i < n; ++i) {
-         uint64_t factor = x_power * p / (i+1);
-         ret += factor;
-         ret -= 2 * (i % 2) * factor;
-         x_power *= x;
-         p /= denom;
-      }
-      return std::make_pair(ret / (denom * denom * denom), denom);
-   }
-
 }

contracts/eosio.system/voting.hpp

@@ -19,6 +19,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cmath>
 
 namespace eosiosystem {
    using eosio::indexed_by;
@@ -233,9 +234,10 @@ namespace eosiosystem {
 
          static system_token_type payment_per_block(uint32_t percent_of_max_inflation_rate) {
             const system_token_type token_supply = currency::get_total_supply();
-            const auto inflation_rate = max_inflation_rate * percent_of_max_inflation_rate;
-            const auto& inflation_ratio = int_logarithm_one_plus(inflation_rate);
-            return (token_supply * inflation_ratio.first) / (inflation_ratio.second * blocks_per_year);
+            const double annual_rate = double(max_inflation_rate * percent_of_max_inflation_rate) / double(10000);
+            double continuous_rate = std::log1p(annual_rate);
+            uint64_t payment = static_cast<uint64_t>((continuous_rate * double(token_supply.quantity)) / double(blocks_per_year));
+            return (system_token_type(payment));
          }
 
          static void update_elected_producers(time cycle_time) {

tests/wasm_tests/eosio.system_tests.cpp

@@ -1054,7 +1054,7 @@ BOOST_FIXTURE_TEST_CASE( proxy_actions_affect_producers, eosio_system_tester ) t
 } FC_LOG_AND_RETHROW()
 
 BOOST_FIXTURE_TEST_CASE(producer_pay, eosio_system_tester) try {
-   issue( "alice", "100000.0000 EOS",  config::system_account_name );
+   issue( "alice", "1000000.0000 EOS",  config::system_account_name );
    fc::variant params = producer_parameters_example(50);
    vector<char> key = fc::raw::pack(get_public_key(N(alice), "active"));