Frequent2Filter.cpp

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#ifndef Frequent2Filter_CPP
#define Frequent2Filter_CPP

#include "common.hpp"  
#include <vector>
//#include <iostream> //for tests

template <class IT_R>
class Frequent2Filter
{
   public:
      Frequent2Filter<IT_R>(IT_R* it_r):
         it_r(it_r), largest_item(it_r->getLargestItem()) { }

      void findFrequentPairs(
         std::vector< std::pair< counter_t, std::pair<item_t, item_t> > >& 
         freq_pairs_with_counters,
         counter_t min_supp);


   private:
      IT_R* it_r;
      const item_t largest_item;
};

template <class IT_R> inline void Frequent2Filter<IT_R>::
findFrequentPairs(
   std::vector< std::pair<counter_t, std::pair<item_t, item_t> > >& 
   freq_pairs_with_counters, counter_t min_supp)
{
   std::vector< std::vector<counter_t> > temp_counter_array;
   temp_counter_array.reserve(largest_item);
   temp_counter_array.resize(largest_item);
   for( item_t index = 0; index < largest_item; ++index) 
   {
      temp_counter_array[index].reserve(largest_item - index );
      temp_counter_array[index].resize(largest_item - index, 0);
   }

   freq_pairs_with_counters.clear();
   it_r->rewind();

   std::vector<item_t> transaction;
   std::vector<item_t>::iterator it1, it2;
   counter_t counter;
   while( (counter = it_r->nextTransactionBIS( transaction )) != 0 )
   {      
      if( transaction.size() > 1)
      {
         for( it1 = transaction.begin(); it1 != transaction.end()-1; ++it1)
         {
            for( it2 = it1+1; it2 != transaction.end(); ++it2)
               temp_counter_array[*it1][*it2 - *it1 - 1] += counter;
         }
      }
   }
   item_t index1, index2;
   std::pair<item_t, item_t> temp_pair;
   std::pair< counter_t, std::pair<item_t, item_t> > temp_pair2;
   for( index1 = 0; index1 < largest_item ; ++index1 )
   {
      for( index2 = 0; index2 < largest_item - index1; ++index2 )
      {
         if( temp_counter_array[index1][index2] >= min_supp )
         {
            temp_pair.first = index1;
            temp_pair.second = index1 + index2 + 1;
            temp_pair2.first = temp_counter_array[index1][index2];
            temp_pair2.second = temp_pair;
            freq_pairs_with_counters.push_back(temp_pair2);
         }
      }
      temp_counter_array[index1].clear();
      std::vector<counter_t>().swap(temp_counter_array[index1]);   
      // temp_counter_array[index1] will never be used again!
   }
}

#endif

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