Convert target -> difficulty #256

steemit · Aug 10, 2016 · 581317f · 581317f
1 parent 8885009
commit 581317f
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Showing 8 changed files with 123 additions and 40 deletions.
diff --git a/libraries/chain/database.cpp b/libraries/chain/database.cpp
@@ -1030,6 +1030,12 @@ fc::sha256 database::get_pow_target()const
    return target;
 }
 
+uint32_t database::get_difficulty_target()const
+{
+   const dynamic_global_property_object& dgp = get_dynamic_global_properties();
+   return ((dgp.num_pow_witnesses/4)+4);
+}
+
 void database::update_witness_schedule4()
 {
    vector<string> active_witnesses;
@@ -2648,6 +2654,7 @@ void database::_apply_block( const signed_block& next_block )
    create_block_summary(next_block);
    clear_expired_transactions();
    clear_expired_orders();
+   clear_work_nonces();
    update_witness_schedule();
 
    update_median_feed();
@@ -3243,6 +3250,18 @@ void database::clear_expired_orders()
    }
 }
 
+void database::clear_work_nonces()
+{
+   auto& idx = get_index_type<work_nonce_index>().indices().get<by_id>();
+   while( true )
+   {
+      auto it = idx.begin();
+      if( it == idx.end() )
+         break;
+      remove(*it);
+   }
+}
+
 void database::adjust_balance( const account_object& a, const asset& delta )
 {
    modify( a, [&]( account_object& acnt )

diff --git a/libraries/chain/include/steemit/chain/database.hpp b/libraries/chain/include/steemit/chain/database.hpp
@@ -93,6 +93,7 @@ namespace steemit { namespace chain {
          bool                       is_known_block( const block_id_type& id )const;
          bool                       is_known_transaction( const transaction_id_type& id )const;
          fc::sha256                 get_pow_target()const;
+         uint32_t                   get_difficulty_target()const;
          block_id_type              get_block_id_for_num( uint32_t block_num )const;
          optional<signed_block>     fetch_block_by_id( const block_id_type& id )const;
          optional<signed_block>     fetch_block_by_number( uint32_t num )const;
@@ -396,6 +397,7 @@ namespace steemit { namespace chain {
          void update_last_irreversible_block();
          void clear_expired_transactions();
          void clear_expired_orders();
+         void clear_work_nonces();
          void process_header_extensions( const signed_block& next_block );
 
          void reset_virtual_schedule_time();

diff --git a/libraries/chain/include/steemit/chain/protocol/steem_operations.hpp b/libraries/chain/include/steemit/chain/protocol/steem_operations.hpp
@@ -597,7 +597,7 @@ namespace steemit { namespace chain {
       string            worker_account;
       block_id_type     prev_block;
       uint64_t          nonce = 0;
-      fc::sha256        work;
+      uint8_t           difficulty = 0;
 
       void create( const block_id_type& prev_block, const string& account_name, uint64_t nonce );
       void validate()const;
@@ -606,11 +606,10 @@ namespace steemit { namespace chain {
    struct pow2_operation : public base_operation
    {
       static_variant<pow2>      work;
-      optional<public_key_type> new_owner_key;    
+      optional<public_key_type> new_owner_key;
       chain_properties          props;
 
       void validate()const;
-      const string& get_worker_account()const { return work.get<pow2>().worker_account; }
 
       /** there is no need to verify authority, the proof of work is sufficient */
       void get_required_active_authorities( flat_set<string>& a )const {  
@@ -778,7 +777,7 @@ FC_REFLECT( steemit::chain::report_over_production_operation, (reporter)(first_b
 FC_REFLECT( steemit::chain::convert_operation, (owner)(requestid)(amount) )
 FC_REFLECT( steemit::chain::feed_publish_operation, (publisher)(exchange_rate) )
 FC_REFLECT( steemit::chain::pow, (worker)(input)(signature)(work) )
-FC_REFLECT( steemit::chain::pow2, (worker_account)(prev_block)(nonce)(work) )
+FC_REFLECT( steemit::chain::pow2, (worker_account)(prev_block)(nonce)(difficulty) )
 FC_REFLECT( steemit::chain::chain_properties, (account_creation_fee)(maximum_block_size)(sbd_interest_rate) );
 
 FC_REFLECT( steemit::chain::pow_operation, (worker_account)(block_id)(nonce)(work)(props) )

diff --git a/libraries/chain/include/steemit/chain/protocol/types.hpp b/libraries/chain/include/steemit/chain/protocol/types.hpp
@@ -118,7 +118,8 @@ namespace steemit { namespace chain {
       impl_owner_authority_history_object_type,
       impl_account_recovery_request_object_type,
       impl_change_recovery_account_request_object_type,
-      impl_escrow_object_type
+      impl_escrow_object_type,
+      impl_work_nonce_object_type
    };
 
    class operation_object;
@@ -302,6 +303,7 @@ FC_REFLECT_ENUM( steemit::chain::impl_object_type,
                  (impl_account_recovery_request_object_type)
                  (impl_change_recovery_account_request_object_type)
                  (impl_escrow_object_type)
+                 (impl_work_nonce_object_type)
                )
 
 FC_REFLECT_TYPENAME( steemit::chain::share_type )

diff --git a/libraries/chain/include/steemit/chain/witness_objects.hpp b/libraries/chain/include/steemit/chain/witness_objects.hpp
@@ -85,8 +85,6 @@ namespace steemit { namespace chain {
          fc::uint128 virtual_scheduled_time = fc::uint128::max_value();
          ///@}
 
-         digest_type last_work;
-
          /**
           * This field represents the Steem blockchain version the witness is running.
           */
@@ -122,6 +120,14 @@ namespace steemit { namespace chain {
          version          majority_version;
    };
 
+   class work_nonce_object : public graphene::db::abstract_object<work_nonce_object>
+   {
+      public:
+         static const uint8_t space_id = implementation_ids;
+         static const uint8_t type_id = impl_work_nonce_object_type;
+
+         uint64_t         nonce = 0;
+   };
 
    struct by_vote_name;
    struct by_name;
@@ -135,7 +141,6 @@ namespace steemit { namespace chain {
       witness_object,
       indexed_by<
          ordered_unique< tag<by_id>, member< object, object_id_type, &object::id > >,
-         ordered_non_unique< tag<by_work>, member<witness_object, digest_type, &witness_object::last_work> >,
          ordered_unique< tag<by_name>, member<witness_object, string, &witness_object::owner> >,
          ordered_non_unique< tag<by_pow>, member<witness_object, uint64_t, &witness_object::pow_worker> >,
          ordered_unique< tag<by_vote_name>,
@@ -177,9 +182,18 @@ namespace steemit { namespace chain {
       > // indexed_by
    > witness_vote_multi_index_type;
 
+   struct by_nonce;
+   typedef multi_index_container<
+      work_nonce_object,
+      indexed_by<
+         ordered_unique< tag<by_id>, member< object, object_id_type, &object::id > >,
+         ordered_unique< tag<by_nonce>, member< work_nonce_object, uint64_t, &work_nonce_object::nonce > >
+      >
+   > work_nonce_multi_index_type;
 
    typedef generic_index< witness_object,         witness_multi_index_type>             witness_index;
    typedef generic_index< witness_vote_object,    witness_vote_multi_index_type >       witness_vote_index;
+   typedef generic_index< work_nonce_object,      work_nonce_multi_index_type >         work_nonce_index;
 } }
 
 FC_REFLECT_DERIVED( steemit::chain::witness_object, (graphene::db::object),
@@ -189,7 +203,6 @@ FC_REFLECT_DERIVED( steemit::chain::witness_object, (graphene::db::object),
                     (last_aslot)(last_confirmed_block_num)(pow_worker)(signing_key)
                     (props)
                     (sbd_exchange_rate)(last_sbd_exchange_update)
-                    (last_work)
                     (running_version)
                     (hardfork_version_vote)(hardfork_time_vote)
                   )
@@ -201,3 +214,9 @@ FC_REFLECT_DERIVED(
    (current_virtual_time)(next_shuffle_block_num)(current_shuffled_witnesses)(median_props)
    (majority_version)
 )
+
+FC_REFLECT_DERIVED(
+   steemit::chain::work_nonce_object,
+   (graphene::db::object),
+   (nonce)
+)
diff --git a/libraries/chain/protocol/steem_operations.cpp b/libraries/chain/protocol/steem_operations.cpp
@@ -190,6 +190,39 @@ namespace steemit { namespace chain {
       work.get<pow2>().validate();
    }
 
+   uint16_t clz_sha256( const fc::sha256& x )
+   {
+      const char* data = x.data();
+      size_t size = x.data_size();
+      size_t lzbits = 0;
+      static const uint8_t char2lzbits[] = {
+     // 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
+        8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+        2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+       };
+
+      size_t i = 0;
+
+      while( true )
+      {
+         uint8_t c = uint8_t( data[i] );
+         lzbits += char2lzbits[c];
+         if( c != 0 )
+            break;
+         ++i;
+         if( i >= size )
+            return 0x100;
+      }
+
+      return lzbits;
+   }
+
    void pow::create( const fc::ecc::private_key& w, const digest_type& i )
    {
       input  = i;
@@ -205,7 +238,6 @@ namespace steemit { namespace chain {
       worker_account = account_name;
       prev_block     = prev;
       nonce          = n;
-      work           = fc::sha256();
 
       auto prv_key = fc::sha256::hash( *this );
       auto input = fc::sha256::hash( prv_key );
@@ -214,7 +246,10 @@ namespace steemit { namespace chain {
       auto sig_hash            = fc::sha256::hash( signature );
       public_key_type recover  = fc::ecc::public_key( signature, sig_hash );
 
-      work = fc::sha256::hash(std::make_pair(input,recover));
+      fc::sha256 work = fc::sha256::hash(std::make_pair(input,recover));
+      uint16_t lzbits = clz_sha256( work );
+      lzbits = (lzbits >= 0x100) ? 0xFF : lzbits;
+      difficulty = uint8_t( lzbits );
    }
 
    void pow::validate()const
@@ -230,7 +265,7 @@ namespace steemit { namespace chain {
    {
       FC_ASSERT( is_valid_account_name( worker_account ) );
       pow2 tmp; tmp.create( prev_block, worker_account, nonce );
-      FC_ASSERT( work == tmp.work );
+      FC_ASSERT( difficulty <= tmp.difficulty );
    }
 
    void feed_publish_operation::validate()const

diff --git a/libraries/chain/steem_evaluator.cpp b/libraries/chain/steem_evaluator.cpp
@@ -2,6 +2,7 @@
 #include <steemit/chain/generic_json_evaluator_registry.hpp>
 #include <steemit/chain/steem_evaluator.hpp>
 #include <steemit/chain/steem_objects.hpp>
+#include <steemit/chain/witness_objects.hpp>
 
 #ifndef IS_LOW_MEM
 #include <diff_match_patch.h>
@@ -1171,17 +1172,14 @@ void pow_apply( database& db, Operation o ) {
 
    FC_ASSERT( db.head_block_time() > STEEMIT_MINING_TIME, "Mining cannot start until ${t}", ("t",STEEMIT_MINING_TIME) );
 
-   if( db.is_producing() || db.has_hardfork( STEEMIT_HARDFORK_0_5__59 ) )  {
-      const auto& witness_by_work = db.get_index_type<witness_index>().indices().get<by_work>();
-      auto work_itr = witness_by_work.find( o.work.work );
-      if( work_itr != witness_by_work.end() ) {
-          FC_ASSERT( !"DUPLICATE WORK DISCOVERED", "${w}  ${witness}",("w",o)("wit",*work_itr) );
-      }
-   }
-
    if( !db.has_hardfork( STEEMIT_HARDFORK_0_12__179 ) )
       FC_ASSERT( o.props.maximum_block_size >= STEEMIT_MIN_BLOCK_SIZE_LIMIT * 2 );
 
+   db.create< work_nonce_object >( [&]( work_nonce_object& wno )
+   {
+      wno.nonce = o.nonce;
+   } );
+
    const auto& accounts_by_name = db.get_index_type<account_index>().indices().get<by_name>();
    auto itr = accounts_by_name.find(o.get_worker_account());
    if(itr == accounts_by_name.end()) {
@@ -1227,7 +1225,6 @@ void pow_apply( database& db, Operation o ) {
       db.modify(*cur_witness, [&]( witness_object& w ){
           w.props             = o.props;
           w.pow_worker        = dgp.total_pow;
-          w.last_work         = o.work.work;
       });
    } else {
       db.create<witness_object>( [&]( witness_object& w )
@@ -1236,7 +1233,6 @@ void pow_apply( database& db, Operation o ) {
           w.props             = o.props;
           w.signing_key       = o.work.worker;
           w.pow_worker        = dgp.total_pow;
-          w.last_work         = o.work.work;
       });
    }
    /// POW reward depends upon whether we are before or after MINER_VOTING kicks in
@@ -1265,26 +1261,30 @@ void pow2_evaluator::do_apply( const pow2_operation& o ) {
 
    database& db = this->db();
 
-   fc::sha256 target = db.get_pow_target();
-   FC_ASSERT( work.work < target, "work lacks sufficient difficulty" );
+   uint32_t target = db.get_difficulty_target();
+   FC_ASSERT( work.prev_block == db.head_block_id() );
+   FC_ASSERT( work.difficulty == target, "incorrect work difficulty" );
 
    FC_ASSERT( o.props.maximum_block_size >= STEEMIT_MIN_BLOCK_SIZE_LIMIT * 2 );
 
-   const auto& witness_by_work = db.get_index_type<witness_index>().indices().get<by_work>();
-   auto work_itr = witness_by_work.find( work.work );
-   if( work_itr != witness_by_work.end() ) {
-       FC_ASSERT( !"DUPLICATE WORK DISCOVERED", "${w}  ${witness}",("w",o)("wit",*work_itr) );
-   }
+   // We discard duplicate PoW by enforcing uniqueness of nonce through a unique index,
+   // which we clear on every block (older work cannot be re-used because it will fail block_id check).
+   // If two workers are unlucky enough to discover work with the same nonce on the same block,
+   // one of them will be rejected -- too bad, it's an extremely rare unlucky situation.
+   db.create< work_nonce_object >( [&]( work_nonce_object& wno )
+   {
+      wno.nonce = work.nonce;
+   } );
 
    const auto& dgp = db.get_dynamic_global_properties();
 
    const auto& accounts_by_name = db.get_index_type<account_index>().indices().get<by_name>();
-   auto itr = accounts_by_name.find(o.get_worker_account());
+   auto itr = accounts_by_name.find( work.worker_account );
    if(itr == accounts_by_name.end()) {
       FC_ASSERT( o.new_owner_key.valid() );
       db.create< account_object >( [&]( account_object& acc )
       {
-         acc.name = o.get_worker_account();
+         acc.name = work.worker_account;
          acc.owner = authority( 1, *o.new_owner_key, 1);
          acc.active = acc.owner;
          acc.posting = acc.owner;
@@ -1311,16 +1311,14 @@ void pow2_evaluator::do_apply( const pow2_operation& o ) {
       db.modify(*cur_witness, [&]( witness_object& w ){
           w.props             = o.props;
           w.pow_worker        = dgp.total_pow;
-          w.last_work         = work.work;
       });
    } else {
       db.create<witness_object>( [&]( witness_object& w )
       {
-          w.owner             = o.get_worker_account();
+          w.owner             = work.worker_account;
           w.props             = o.props;
           w.signing_key       = *o.new_owner_key;
           w.pow_worker        = dgp.total_pow;
-          w.last_work         = work.work;
       });
    }
    /// POW reward depends upon whether we are before or after MINER_VOTING kicks in