median_tpl.h

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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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 *       - Pierre-Henri WUILLEMIN(_at_LIP6)                                 *
 *       - Christophe GONZALES(_at_AMU)                                     *
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#pragma once
 

 
#include <sstream>
#include <vector>
 
// to ease parser in IDEs
#include <agrum/base/multidim/aggregators/median.h>
#include <agrum/base/multidim/aggregators/multiDimAggregator.h>
 
namespace gum {
 
  namespace aggregator {
    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::Median() : MultiDimAggregator< GUM_SCALAR >() {
      GUM_CONSTRUCTOR(Median);
    }
 
    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::Median(const Median< GUM_SCALAR >& from) :
        MultiDimAggregator< GUM_SCALAR >(from) {
      GUM_CONS_CPY(Median);
    }
 
    template < typename GUM_SCALAR >
    INLINE Median< GUM_SCALAR >::~Median() {
      GUM_DESTRUCTOR(Median);
    }
 
    template < typename GUM_SCALAR >
    INLINE std::string Median< GUM_SCALAR >::aggregatorName() const {
      std::stringstream ss;
      ss << "median";
      return ss.str();
    }
 
    template < typename GUM_SCALAR >
    INLINE MultiDimContainer< GUM_SCALAR >* Median< GUM_SCALAR >::newFactory() const {
      return new Median< GUM_SCALAR >();
    }
 
    template < typename GUM_SCALAR >
    Idx Median< GUM_SCALAR >::buildValue_(const gum::Instantiation& i) const {
      if (i.nbrDim() < 2) return i.nbrDim() / 2;   // arbitrary. Guess = (max-min)/2 .
 
      // we assume that every (parent) variable has the same domainSize
      Idx maxVal = i.variable(1).domainSize();
 
      std::vector< Idx > cum(maxVal, 0);
 
      for (Idx j = 1; j < this->nbrDim(); j++)
        cum[i.val(j)]++;
 
      Idx half = (this->nbrDim() + 1) / 2;   // 50% of the population
 
      Idx max = maxVal;
      for (Idx j = 0, sumcum = 0; j < maxVal; j++)
        if ((sumcum += cum[j]) >= half) {
          max = j;
          break;
        }
      Idx maxR = maxVal;
      for (Idx j = maxVal - 1, jj = 0, sumcum = 0; jj < maxVal; jj++, j--)
        if ((sumcum += cum[j]) >= half) {
          maxR = j;
          break;
        }
 
      // multiDimAggregator::get will truncate if needed.
      return (maxR + max) / 2;
    }
 
    template < typename GUM_SCALAR >
    INLINE Idx Median< GUM_SCALAR >::fold_(const DiscreteVariable& v,
                                           Idx                     i1,
                                           Idx                     i2,
                                           bool&                   stop_iteration) const {
      return 0;
    }
 
  }   // namespace aggregator
}   // namespace gum