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HashStatistic.h

//
// HashStatistic.h
//
// $Id: //poco/1.3/Foundation/include/Poco/HashStatistic.h#1 $
//
// Library: Foundation
// Package: Hashing
// Module:  HashStatistic
//
// Definition of the HashStatistic class.
//
// Copyright (c) 2006, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_HashStatistic_INCLUDED
#define Foundation_HashStatistic_INCLUDED


#include "Poco/Foundation.h"
#include <vector>


namespace Poco {


//@ deprecated
00051 class Foundation_API HashStatistic
      /// HashStatistic class bundles statistical information on the current state of a HashTable
{
public:
      HashStatistic(
            UInt32 tableSize, 
            UInt32 numEntries, 
            UInt32 numZeroEntries, 
            UInt32 maxEntry, 
            std::vector<UInt32> details = std::vector<UInt32>());
            /// Creates the HashStatistic.

      virtual ~HashStatistic();
            /// Destroys the HashStatistic.

      UInt32 maxPositionsOfTable() const;
            /// Returns the maximum number of different hash values possible for the table

      UInt32 numberOfEntries() const;
            /// Returns the total number of entries currently stored in the HashTable

      UInt32 numberOfZeroPositions() const;
            /// Returns the number of hash positions that contain no entry.

      double avgEntriesPerHash() const;
            /// Returns the average number of entries per position in the Hashtable, the higher this value the less efficient
            /// performs hashing. If a large value is returned and getNumberOfZeroPositions also returns a large value, this
            /// indicates an inefficient hashing function. If the number of zero entries is low, resizing the HashTable, should
            /// be enough to improve performance

      double avgEntriesPerHashExclZeroEntries() const;
            /// Same as getAvgEntriesPerHash but hash values that contain no entry are ignored,
            /// getAvgEntriesPerHashExclZeroEntries >= getAvgEntriesPerHash will always be true.

      UInt32 maxEntriesPerHash() const;
            /// Returns the maximum number of entries per hash value found in the current table.

      const std::vector<UInt32> detailedEntriesPerHash() const;
            /// Will either be an empty vector or will contain for each possible hash value, the number of entries currently stored

      std::string toString() const;
            /// Converts the whole data structure into a string.

private:
00095       UInt32 _sizeOfTable;
      UInt32 _numberOfEntries;
      UInt32 _numZeroEntries;
      UInt32 _maxEntriesPerHash;
      std::vector<UInt32> _detailedEntriesPerHash;
};


00103 inline UInt32 HashStatistic::maxPositionsOfTable() const
{
      return _sizeOfTable;
}


00109 inline UInt32 HashStatistic::numberOfEntries() const
{
      return _numberOfEntries;
}


00115 inline UInt32 HashStatistic::numberOfZeroPositions() const
{
      return _numZeroEntries;
}


00121 inline double HashStatistic::avgEntriesPerHash() const
{
      return ((double) numberOfEntries()) / maxPositionsOfTable();
}


00127 inline double HashStatistic::avgEntriesPerHashExclZeroEntries() const
{
      return ((double) numberOfEntries()) / (maxPositionsOfTable() - numberOfZeroPositions());
}


00133 inline UInt32 HashStatistic::maxEntriesPerHash() const
{
      return _maxEntriesPerHash;
}


00139 inline const std::vector<UInt32> HashStatistic::detailedEntriesPerHash() const
{
      return _detailedEntriesPerHash;
}


} // namespace Poco


#endif // Foundation_HashStatistic_INCLUDED

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