www.pudn.com > libpmk.rar > histogram.h, change:2007-05-27,size:4396b


// Copyright 2007, Massachusetts Institute of Technology.
// The use of this code is permitted for research only. There is
// absolutely no warranty for this software.
//
// Author: John Lee (jjl@mit.edu)
//
#ifndef HISTOGRAMS_HISTOGRAM_H
#define HISTOGRAMS_HISTOGRAM_H

#include <string>
#include <iostream>
#include "histograms/bin.h"

using namespace std;

namespace libpmk {
/// A sparse representation for a flat (1-D) histogram.
/**
 * Note that this implementation sorts and consolidates bins lazily,
 * meaning that there can be bins with duplicate indices in the
 * internal structure. However, the public interface behaves as though
 * the internal data is always sorted and consolidated, so there is no
 * need to worry about duplicate bins or unsorted bins when accessing
 * elements using any of the public methods.
 */
class Histogram {
 public:
   Histogram();
   ~Histogram();

   /// Adds a copy of <new_bin> to the histogram.
   /**
    * By "adding a bin", we mean looking for the Bin in this histogram
    * that has the same index (the LargeIndex identifier) as <new_bin>
    * and increasing the count by that much. It also will set the size
    * of the bin to be the <b>maximum</b> of the two bin sizes. The
    * parent, child, and sibling pointers of <new_bin> are completely
    * ignored.
    */
   Bin* AddBin(const Bin& new_bin);

   /// Sorts and consolidates bins.
   /**
    * It is not necessary to call this manually, as all of the sorting
    * and consolidation is done automatically (lazily). However, for
    * performance reasons, you may call this manually.
    */
   void SortBins() const;

   /// Gets the total number of bins with unique index.
   int GetNumBins() const;

   /// Assuming the Bins are sorted, gets the <ii>th bin in the ordering.
   /**
    * The Bins are sorted in order of increasing index.
    */
   const Bin* GetBin(int ii);

   /// Gets the bin with the given index.
   /**
    * This will return NULL if no such Bin is found.
    */
   const Bin* GetBin(const LargeIndex& index);

   /// Gets the Bin with the given index after the <finger>th Bin.
   /**
    * This does a linear search for the Bin with the given index, but
    * begins the search from the <finger>th Bin in the sorted list
    * of all Bins.
    */ 
   const Bin* GetBin(const LargeIndex& index, int finger);

   // We pass pointers instead of const references, since this function has
   // the capability to modify the histograms themselves (by sorting their
   // contents).
   /// Compute the histogram intersection.
   static double ComputeIntersection(Histogram* first, Histogram* second);

   /// Write a vector of Histograms to a stream.
   /**
    * The output format is as follows: <ul>
    * <li> (int32) N, the number of histograms
    * <li> (N * Histogram) the histograms.</ul>
    */
   static void WriteToStream(ostream& output_stream,
                             const vector<Histogram*>& histograms);

   /// Write a single Histogram to a stream.
   /**
    * The output format is as follows: <ul>
    * <li> (int32) B, the number of bins
    * <li> For each bin: <ul>
    *    <li> (int32) S, the size of the LargeIndex identifier
    *    <li> (S * int32) the index
    *    <li> (double) size
    *    <li> (double) count
    *
    * The bins are sorted before they are written. They are sorted in
    * order of increasing index.
    */
   static void WriteSingleHistogramToStream(ostream& output_stream,
                                            Histogram* h);

   
   /// Read a vector of Histograms from a stream.
   /**
    * This function allocates new memory for the histograms. The
    * caller is responsible for freeing it. For the file format, see
    * WriteToStream.
    * \sa WriteToStream
    */
   static vector<Histogram*> ReadFromStream(istream& input_stream);

   /// Read a single Histogram from a stream.
   /**
    * This function allocates new memory for the histogram. The caller
    * is responsible for freeing it. For the file format, see
    * ReadFromStream.
    * \sa ReadFromStream
    */
   static Histogram* ReadSingleHistogramFromStream(istream& input_stream);

 private:
   // Disallow evil constructors
   Histogram(const Histogram&);
   Histogram& operator=(const Histogram&);

   mutable vector<Bin*> bins_;
   mutable bool is_sorted_;
};
}  // namespace libpmk

#endif  // HISTOGRAMS_HISTOGRAM_H