Implement recent_slots_filled and use it to measure witness participation

libraries/chain/db_getter.cpp

@@ -73,14 +73,4 @@ node_property_object& database::node_properties()
    return _node_property_object;
 }
 
-double database::witness_participation_rate()const
-{
-    if( head_block_num() < 10 ) return 1; // sample size is too small
-    uint32_t produced = std::min<uint32_t>( head_block_num()-1, 100 );
-    auto prior = fetch_block_by_number( head_block_num() - produced );
-    auto delta_time = head_block_time() - prior->timestamp;
-    auto expected_slots = delta_time.to_seconds() / get_global_properties().parameters.block_interval;
-    return double(produced) / expected_slots;
-}
-
 } }

libraries/chain/db_init.cpp

@@ -525,6 +525,8 @@ void database::init_genesis(const genesis_state_type& genesis_state)
          _wso.scheduler.produce_schedule(rng);
 
       _wso.last_scheduling_block = 0;
+
+      _wso.recent_slots_filled = fc::uint128::max_value();
    });
    assert( wso.id == witness_schedule_id_type() );
 

libraries/chain/db_witness_schedule.cpp

@@ -141,6 +141,16 @@ void database::update_witness_schedule(const signed_block& next_block)
             memcpy(_wso.rng_seed.begin(), dpo.random.data(), dpo.random.data_size());
       }
       _wso.last_scheduling_block = next_block.block_num();
+      _wso.recent_slots_filled = (
+           (_wso.recent_slots_filled << 1)
+           + 1) << (schedule_slot - 1);
    });
 }
+
+uint32_t database::witness_participation_rate()const
+{
+   const witness_schedule_object& wso = get(witness_schedule_id_type());
+   return uint64_t(GRAPHENE_100_PERCENT) * wso.recent_slots_filled.popcount() / 128;
+}
+
 } }

libraries/chain/include/graphene/chain/database.hpp

@@ -138,9 +138,9 @@ namespace graphene { namespace chain {
 
          /**
           *  Calculate the percent of block production slots that were missed in the
-          *  past 100 blocks.  
+          *  past 128 blocks, not including the current block.
           */
-         double witness_participation_rate()const;
+         uint32_t witness_participation_rate()const;
 
          void                              add_checkpoints( const flat_map<uint32_t,block_id_type>& checkpts );
          const flat_map<uint32_t,block_id_type> get_checkpoints()const { return _checkpoints; }

libraries/chain/include/graphene/chain/global_property_object.hpp

@@ -16,6 +16,8 @@
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 #pragma once
+#include <fc/uint128.hpp>
+
 #include <graphene/chain/protocol/chain_parameters.hpp>
 #include <graphene/chain/database.hpp>
 #include <graphene/db/object.hpp>

libraries/chain/include/graphene/chain/witness_schedule_object.hpp

@@ -19,6 +19,7 @@
 
 // needed to serialize witness_scheduler
 #include <fc/container/deque.hpp>
+#include <fc/uint128.hpp>
 
 #include <graphene/chain/protocol/types.hpp>
 #include <graphene/chain/witness_scheduler.hpp>
@@ -57,6 +58,12 @@ class witness_schedule_object : public abstract_object<witness_schedule_object>
       uint32_t last_scheduling_block;
       uint64_t slots_since_genesis = 0;
       fc::array< char, sizeof(secret_hash_type) > rng_seed;
+
+      /**
+       * Not necessary for consensus, but used for figuring out the participation rate.
+       * The nth bit is 0 if the nth slot was unfilled, else it is 1.
+       */
+      fc::uint128 recent_slots_filled;
 };
 
 } }
@@ -77,4 +84,5 @@ FC_REFLECT_DERIVED( graphene::chain::witness_schedule_object, (graphene::chain::
                     (last_scheduling_block)
                     (slots_since_genesis)
                     (rng_seed)
+                    (recent_slots_filled)
                     )

libraries/fc

@@ -1 +1 @@
-Subproject commit 0391665471b4dffb7af951853a777565a7ae9a74
+Subproject commit 5f43c06bae6d03e319dd2f230fe7cbd74399a773

libraries/plugins/witness/include/graphene/witness/witness.hpp

@@ -57,7 +57,7 @@ private:
    boost::program_options::variables_map _options;
    bool _production_enabled = false;
    bool _consecutive_production_enabled = false;
-   int  _required_witness_participation = 33;
+   uint32_t _required_witness_participation = 33 * GRAPHENE_1_PERCENT;
 
    std::map<chain::public_key_type, fc::ecc::private_key> _private_keys;
    std::set<chain::witness_id_type> _witnesses;

libraries/plugins/witness/witness.cpp

@@ -39,7 +39,7 @@ void witness_plugin::plugin_set_program_options(
    string witness_id_example = fc::json::to_string(chain::witness_id_type());
    command_line_options.add_options()
          ("enable-stale-production", bpo::bool_switch()->notifier([this](bool e){_production_enabled = e;}), "Enable block production, even if the chain is stale.")
-         ("required-participation", bpo::bool_switch()->notifier([this](int e){_required_witness_participation = e;}), "Percent of witnesses (0-99) that must be participating in order to produce blocks")
+         ("required-participation", bpo::bool_switch()->notifier([this](int e){_required_witness_participation = uint32_t(e*GRAPHENE_1_PERCENT);}), "Percent of witnesses (0-99) that must be participating in order to produce blocks")
          ("allow-consecutive", bpo::bool_switch()->notifier([this](bool e){_consecutive_production_enabled = e;}), "Allow block production, even if the last block was produced by the same witness.")
          ("witness-id,w", bpo::value<vector<string>>()->composing()->multitoken(),
           ("ID of witness controlled by this node (e.g. " + witness_id_example + ", quotes are required, may specify multiple times)").c_str())
@@ -191,11 +191,11 @@ void witness_plugin::block_production_loop()
          return false;
       }
 
-      double prate = db.witness_participation_rate();
+      uint32_t prate = db.witness_participation_rate();
-      if( int(100*prate)  < _required_witness_participation ) 
+      if( prate < _required_witness_participation )
       {
          elog("Not producing block because node appers to be on a minority fork with only ${x}% witness participation",
-              ("x",uint32_t(100*prate) ) );
+              ("x",uint32_t(100*uint64_t(prate) / GRAPHENE_1_PERCENT) ) );
          return false;
       }