Implement square root curation curve #1052

libraries/chain/database.cpp

@@ -3846,6 +3846,24 @@ void database::apply_hardfork( uint32_t hardfork )
                rfo.author_reward_curve = curve_id::linear;
                rfo.curation_reward_curve = curve_id::square_root;
             });
+
+            const auto& cidx = get_index< comment_index, by_cashout_time >();
+            const auto& vidx = get_index< comment_vote_index, by_comment_voter >();
+            for( auto c_itr = cidx.begin(); c_itr != cidx.end() && c_itr->cashout_time != fc::time_point_sec::maximum(); ++c_itr )
+            {
+               modify( *c_itr, [&]( comment_object& c )
+               {
+                  c.total_vote_weight = c.total_sqrt_vote_weight;
+               });
+
+               for( auto v_itr = vidx.lower_bound( c_itr->id ); v_itr != vidx.end() && v_itr->comment == c_itr->id; ++v_itr )
+               {
+                  modify( *v_itr, [&]( comment_vote_object& v )
+                  {
+                     v.weight = v.sqrt_weight;
+                  });
+               }
+            }
          }
          break;
       default:

libraries/chain/hardfork.d/0_19.hf

@@ -10,6 +10,7 @@
 #define STEEMIT_HARDFORK_0_19__987 (STEEMIT_HARDFORK_0_19)
 #define STEEMIT_HARDFORK_0_19__997 (STEEMIT_HARDFORK_0_19)
 #define STEEMIT_HARDFORK_0_19__1051 (STEEMIT_HARDFORK_0_19)
+#define STEEMIT_HARDFORK_0_19__1052 (STEEMIT_HARDFORK_0_19)
 #define STEEMIT_HARDFORK_0_19__1053 (STEEMIT_HARDFORK_0_19)
 
 #define STEEMIT_HARDFORK_0_19_VERSION hardfork_version( 0, 19 )

libraries/chain/include/steemit/chain/comment_object.hpp

@@ -78,6 +78,7 @@ namespace steemit { namespace chain {
          time_point_sec    cashout_time; /// 24 hours from the weighted average of vote time
          time_point_sec    max_cashout_time;
          uint64_t          total_vote_weight = 0; /// the total weight of voting rewards, used to calculate pro-rata share of curation payouts
+         uint64_t          total_sqrt_vote_weight = 0; /// Temporary total weight of votes for post hf19 curation reward curve
 
          uint16_t          reward_weight = 0;
 
@@ -120,6 +121,7 @@ namespace steemit { namespace chain {
          account_id_type   voter;
          comment_id_type   comment;
          uint64_t          weight = 0; ///< defines the score this vote receives, used by vote payout calc. 0 if a negative vote or changed votes.
+         uint64_t          sqrt_weight = 0; ///< Temporary vote weight for post hf19 curation curve
          int64_t           rshares = 0; ///< The number of rshares this vote is responsible for
          int16_t           vote_percent = 0; ///< The percent weight of the vote
          time_point_sec    last_update; ///< The time of the last update of the vote
@@ -250,13 +252,13 @@ FC_REFLECT( steemit::chain::comment_object,
              (depth)(children)
              (net_rshares)(abs_rshares)(vote_rshares)
              (children_abs_rshares)(cashout_time)(max_cashout_time)
-             (total_vote_weight)(reward_weight)(total_payout_value)(curator_payout_value)(beneficiary_payout_value)(author_rewards)(net_votes)(root_comment)
+             (total_vote_weight)(total_sqrt_vote_weight)(reward_weight)(total_payout_value)(curator_payout_value)(beneficiary_payout_value)(author_rewards)(net_votes)(root_comment)
              (max_accepted_payout)(percent_steem_dollars)(allow_replies)(allow_votes)(allow_curation_rewards)
              (beneficiaries)
           )
 CHAINBASE_SET_INDEX_TYPE( steemit::chain::comment_object, steemit::chain::comment_index )
 
 FC_REFLECT( steemit::chain::comment_vote_object,
-             (id)(voter)(comment)(weight)(rshares)(vote_percent)(last_update)(num_changes)
+             (id)(voter)(comment)(weight)(sqrt_weight)(rshares)(vote_percent)(last_update)(num_changes)
           )
 CHAINBASE_SET_INDEX_TYPE( steemit::chain::comment_vote_object, steemit::chain::comment_vote_index )

libraries/chain/steem_evaluator.cpp

@@ -1290,6 +1290,7 @@ void vote_evaluator::do_apply( const vote_operation& o )
       old_rshares = util::evaluate_reward_curve( old_rshares );
 
       uint64_t max_vote_weight = 0;
+      uint64_t sqrt_max_vote_weight = 0;
 
       /** this verifies uniqueness of voter
        *
@@ -1345,6 +1346,13 @@ void vote_evaluator::do_apply( const vote_operation& o )
                   uint64_t old_weight = util::evaluate_reward_curve( old_vote_rshares.value, reward_fund.curation_reward_curve, reward_fund.content_constant ).to_uint64();
                   uint64_t new_weight = util::evaluate_reward_curve( comment.vote_rshares.value, reward_fund.curation_reward_curve, reward_fund.content_constant ).to_uint64();
                   cv.weight = new_weight - old_weight;
+                  if( !_db.has_hardfork( STEEMIT_HARDFORK_0_19__1052 ) )
+                  {
+                     old_weight = util::evaluate_reward_curve( old_vote_rshares.value, curve_id::square_root ).to_uint64();
+                     new_weight = util::evaluate_reward_curve( comment.vote_rshares.value, curve_id::square_root ).to_uint64();
+                     cv.sqrt_weight = new_weight - old_weight;
+                     sqrt_max_vote_weight = cv.sqrt_weight;
+                  }
                }
                else if ( _db.has_hardfork( STEEMIT_HARDFORK_0_1 ) )
                {
@@ -1371,6 +1379,14 @@ void vote_evaluator::do_apply( const vote_operation& o )
                w *= delta_t;
                w /= STEEMIT_REVERSE_AUCTION_WINDOW_SECONDS;
                cv.weight = w.to_uint64();
+
+               if( _db.has_hardfork( STEEMIT_HARDFORK_0_17 ) )
+               {
+                  uint128_t w(sqrt_max_vote_weight);
+                  w *= delta_t;
+                  w /= STEEMIT_REVERSE_AUCTION_WINDOW_SECONDS;
+                  cv.sqrt_weight = w.to_uint64();
+               }
             }
          }
          else
@@ -1384,6 +1400,7 @@ void vote_evaluator::do_apply( const vote_operation& o )
          _db.modify( comment, [&]( comment_object& c )
          {
             c.total_vote_weight += max_vote_weight;
+            c.total_sqrt_vote_weight = sqrt_max_vote_weight;
          });
       }
       if( !_db.has_hardfork( STEEMIT_HARDFORK_0_17__774) )

libraries/chain/util/reward.cpp

@@ -4,6 +4,37 @@
 
 namespace steemit { namespace chain { namespace util {
 
+uint8_t find_msb( const uint128_t& u )
+{
+   uint64_t x;
+   uint8_t places;
+   x      = (u.lo ? u.lo : 1);
+   places = (u.hi ?   64 : 0);
+   x      = (u.hi ? u.hi : x);
+   return uint8_t( boost::multiprecision::detail::find_msb(x) + places );
+}
+
+uint64_t approx_sqrt( const uint128_t& x )
+{
+   if( (x.lo == 0) && (x.hi == 0) )
+      return 0;
+
+   uint8_t msb_x = find_msb(x);
+   uint8_t msb_z = msb_x >> 1;
+
+   uint128_t msb_x_bit = uint128_t(1) << msb_x;
+   uint64_t  msb_z_bit = uint64_t (1) << msb_z;
+
+   uint128_t mantissa_mask = msb_x_bit - 1;
+   uint128_t mantissa_x = x & mantissa_mask;
+   uint64_t mantissa_z_hi = (msb_x & 1) ? msb_z_bit : 0;
+   uint64_t mantissa_z_lo = (mantissa_x >> (msb_x - msb_z)).lo;
+   uint64_t mantissa_z = (mantissa_z_hi | mantissa_z_lo) >> 1;
+   uint64_t result = msb_z_bit | mantissa_z;
+
+   return result;
+}
+
 uint64_t get_rshare_reward( const comment_reward_context& ctx )
 {
    try
@@ -53,7 +84,7 @@ uint128_t evaluate_reward_curve( const uint128_t& rshares, const curve_id& curve
          }
          break;
       case linear:
-         result = rshares;
+         result = approx_sqrt( rshares );
          break;
       case square_root:
          break;