intense_tests: Implement generic_scheduler_mc_test

tests/intense/block_tests.cpp

@@ -26,6 +26,7 @@
 #include <graphene/chain/key_object.hpp>
 #include <graphene/chain/account_object.hpp>
 #include <graphene/chain/proposal_object.hpp>
+#include <graphene/chain/witness_schedule_object.hpp>
 
 #include <fc/crypto/digest.hpp>
 
@@ -310,4 +311,92 @@ BOOST_FIXTURE_TEST_CASE( delegate_groups_mc_test, database_fixture )
    }
 }
 
+/**
+ *  To have a secure random number we need to ensure that the same
+ *  delegate does not get to produce two blocks in a row.  There is
+ *  always a chance that the last delegate of one round will be the
+ *  first delegate of the next round.
+ *
+ *  This means that when we shuffle delegates we need to make sure
+ *  that there is at least N/2 delegates between consecutive turns
+ *  of the same delegate.    This means that durring the random
+ *  shuffle we need to restrict the placement of delegates to maintain
+ *  this invariant.
+ *
+ *  This test checks the requirement using Monte Carlo approach
+ *  (produce lots of blocks and check the invariant holds).
+ */
+BOOST_FIXTURE_TEST_CASE( generic_scheduler_mc_test, database_fixture )
+{
+   try {
+      size_t num_witnesses = db.get_global_properties().active_witnesses.size();
+      size_t dmin = num_witnesses >> 1;
+      witness_scheduler_rng rng(
+         // - - - - + - - - - 1 - - - - + - - - - 2 - - - - + - - -
+          "\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"
+          );
+      witness_scheduler scheduler;
+      vector< witness_id_type > witness_ids;
+
+      witness_ids.reserve( num_witnesses );
+      for( size_t i=0; i<num_witnesses; i++ )
+         witness_ids.push_back( witness_id_type(i) );
+
+      scheduler._min_token_count = num_witnesses / 2;
+
+      scheduler.insert_all( witness_ids );
+      for( size_t i=0; i<num_witnesses; i++ )
+         scheduler.produce_schedule( rng );
+
+      vector< witness_id_type > cur_round;
+      vector< witness_id_type > full_schedule;
+      // if we make the maximum witness count testable,
+      // we'll need to enlarge this.
+      std::bitset< 0x40 > witness_seen;
+      size_t total_blocks = 1000000;
+
+      cur_round.reserve( num_witnesses );
+      full_schedule.reserve( total_blocks );
+
+      // we assert so the test doesn't continue, which would
+      // corrupt memory
+      assert( num_witnesses <= witness_seen.size() );
+
+      while( full_schedule.size() < total_blocks )
+      {
+         scheduler.produce_schedule( rng );
+         witness_id_type wid = scheduler.consume_schedule();
+         full_schedule.push_back( wid );
+         cur_round.push_back( wid );
+         if( cur_round.size() == num_witnesses )
+         {
+            // check that the current round contains exactly 1 copy
+            // of each witness
+            witness_seen.reset();
+            for( const witness_id_type& w : cur_round )
+            {
+               uint64_t inst = w.instance.value;
+               BOOST_CHECK( !witness_seen.test( inst ) );
+               assert( !witness_seen.test( inst ) );
+               witness_seen.set( inst );
+            }
+            cur_round.clear();
+         }
+      }
+
+      for( size_t i=0,m=full_schedule.size(); i<m; i++ )
+      {
+         for( size_t j=i+1,n=std::min( m, i+dmin ); j<n; j++ )
+         {
+            BOOST_CHECK( full_schedule[i] != full_schedule[j] );
+            assert( full_schedule[i] != full_schedule[j] );
+         }
+      }
+
+   } catch (fc::exception& e) {
+      edump((e.to_detail_string()));
+      throw;
+   }
+}
+
 BOOST_AUTO_TEST_SUITE_END()