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ListCache.hpp

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//
// ListCache
//
// 24 September 2004 -- tds
//
// Stores previously used precomputed lists.
//

#ifndef INDRI_LISTCACHE_HPP
#define INDRI_LISTCACHE_HPP

#include <vector>
#include "indri/delete_range.hpp"
#include "indri/SimpleCopier.hpp"
#include "indri/DocumentCount.hpp"
#include "indri/QuerySpec.hpp"
#include "indri/TreePrinterWalker.hpp"
#include "indri/Parameters.hpp"

class ListCache {
public:
  struct CachedList {
    // query structure
    SimpleCopier raw;
    SimpleCopier context;

    // postings
    greedy_vector<DocumentContextCount> entries;

    // statistics about the entries
    INT64 occurrences;
    INT64 contextSize;
    INT64 minimumContextSize;
    INT64 maximumContextSize;
    INT64 maximumOccurrences;
    float maximumContextFraction;
  };

private:
  std::vector<struct CachedList*> _lists;

public:
  ~ListCache() {
    delete_vector_contents( _lists );
  }

  void add( CachedList* list ) {
    if( _lists.size() > 100 ) {
      delete _lists[0];
      _lists.erase( _lists.begin() );
    }

    _lists.push_back( list );
  }

  CachedList* find( indri::lang::Node* raw, indri::lang::Node* context ) {
    ListCache::CachedList* list = 0;
    size_t i = 0;

    // TODO: use a hash function to make this faster
    for( i=0; i<_lists.size(); i++ ) {
      indri::lang::Node* cachedRaw = _lists[i]->raw.root();
      indri::lang::Node* cachedContext = _lists[i]->context.root();

      if( *cachedRaw == *raw ) {
        if( ( !cachedContext && !context ) ||
            ( cachedContext && context && (*context == *cachedContext)) ) {
          list = _lists[i];
          break;
        } 
      }
    }

    return list;
  }
};

#endif // INDRI_LISTCACHE_HPP

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