---

WeightFoldingCopier.hpp

Go to the documentation of this file.

//
// WeightFoldingCopier
//
// 17 September 2004 -- tds
//

#ifndef INDRI_WEIGHTFOLDINGCOPIER_HPP
#define INDRI_WEIGHTFOLDINGCOPIER_HPP

class WeightFoldingCopier : public indri::lang::Copier {
private:
  std::vector<indri::lang::Node*> _nodes;

public:
  ~WeightFoldingCopier() {
    delete_vector_contents( _nodes );
  }

  indri::lang::Node* defaultAfter( indri::lang::Node* old, indri::lang::Node* newNode ) {
    _nodes.push_back( newNode );
    return newNode;
  }

  indri::lang::Node* after( indri::lang::WeightNode* oldWeightNode, indri::lang::WeightNode* newWeightNode ) {
    indri::lang::WeightNode* newerWeightNode = new indri::lang::WeightNode();
    const std::vector< std::pair<double, indri::lang::ScoredExtentNode*> >& children = newWeightNode->getChildren();
    
    for( size_t i=0; i<children.size(); i++ ) {
      // is this a weight node?
      indri::lang::WeightNode* childWeightNode = dynamic_cast<indri::lang::WeightNode*>( children[i].second );

      // is this a combine node?
      indri::lang::CombineNode* childCombineNode = dynamic_cast<indri::lang::CombineNode*>( children[i].second );

      if( !childWeightNode && !childCombineNode ) {
        // child is not a weight node, so just add it directly
        newerWeightNode->addChild( children[i].first, children[i].second );
      } else if( childCombineNode ) {
        const std::vector< indri::lang::ScoredExtentNode* >& grandkids = childCombineNode->getChildren();
        double kidWeight = children[i].first / double(grandkids.size());
        
        for( size_t j=0; j<grandkids.size(); j++ ) {
          newerWeightNode->addChild( kidWeight, grandkids[j] );
        }
      } else {
        // child _is_ a weight node, so we're going to fold all its children up to this level
        const std::vector< std::pair<double, indri::lang::ScoredExtentNode*> >& grandkids = childWeightNode->getChildren();
        double parentWeight = children[i].first;
        double normalizer = 0.0;

        // need to normalize all weights to sum to 1
        for( size_t j=0; j<grandkids.size(); j++ ) {
          normalizer += grandkids[j].first;
        }
    
        for( size_t j=0; j<grandkids.size(); j++ ) {
          // have to normalize the weight by including the parent weight as well
          newerWeightNode->addChild( parentWeight * grandkids[j].first / normalizer,
                                     grandkids[j].second );
        }
      }
    }

    newerWeightNode->setNodeName( newWeightNode->nodeName() );
    delete newWeightNode;
    _nodes.push_back( newerWeightNode );

    return newerWeightNode;
  }
};

#endif // INDRI_WEIGHTFOLDINGCOPIER_HPP

---