SZaru::UniqueEstimator Class Reference

Statistical estimators for the total number of unique data items. More...

#include <szaru.h>

List of all members.

Public Member Functions
virtual void	AddElem (const std::string &elm)=0
	Add a new element to this entry.
virtual void	AddElemInCIF (const char *data, size_t size)=0
	Add a new element to this entry in C sylte interface.
virtual int64_t	Estimate () const =0
	Estimate the number of unique entries.
virtual uint64_t	TotElems () const =0
	Get the number of elements added to this entry in the table.
Static Public Member Functions
static UniqueEstimator *	Create (int nElemes)
	Create a UniqueEstimator object.

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Detailed Description

Statistical estimators for the total number of unique data items.

Structure for calculating the number of unique elements.

The technique used is:

• Convert all elements to unique evenly spaced hash keys.
• Keep track of the smallest N element ("nElemes") of these elements.
• "nelems" cannot glow beyond maxelems.
• Based on the coverage of the space, compute an estimate of the total number of unique elements, where biggest-small-elem means largest element among kept "maxelems" elements.

unique = nElemes < maxelems ? nElems : (maxelems << bits-in-hash) / biggest-small-elem

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Member Function Documentation

virtual void SZaru::UniqueEstimator::AddElem

(

const std::string &

elm

)

[pure virtual]

Add a new element to this entry.

Parameters:

elm

element to add

virtual void SZaru::UniqueEstimator::AddElemInCIF	(	const char *	data,
		size_t	size
	)			[pure virtual]

Add a new element to this entry in C sylte interface.

Parameters:

	data	element data
	size	element size

static UniqueEstimator* SZaru::UniqueEstimator::Create

(

int

nElemes

)

[static]

Create a UniqueEstimator object.

Parameters:

nElemes

tuning parameter. If nElemes is bigger, the estimation becomes more accurate but consuming more memory.

virtual int64_t SZaru::UniqueEstimator::Estimate

(

)

const [pure virtual]

Estimate the number of unique entries.

Returns:

the estimated number of unique entries.

virtual uint64_t SZaru::UniqueEstimator::TotElems

(

)

const [pure virtual]

Get the number of elements added to this entry in the table.

Returns:

the number of added elements

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The documentation for this class was generated from the following file:

• src/szaru.h