itk::CompensatedSummation< TFloat > Class Template Reference

#include <itkCompensatedSummation.h>

Collaboration diagram for itk::CompensatedSummation< TFloat >:

Detailed Description

template<class TFloat>
class itk::CompensatedSummation< TFloat >

Perform more precise accumulation of floating point numbers.

The float and double datatypes only have finite precision. When performing a running sum of floats, the accumulated errors get progressively worse as the magnitude of the sum gets large relative to new elements.

From Wikipedia, http://en.wikipedia.org/wiki/Kahan_summation_algorithm

"In numerical analysis, the Kahan summation algorithm (also known as compensated summation) significantly reduces the numerical error in the total obtained by adding a sequence of finite precision floating point numbers, compared to the obvious approach. This is done by keeping a separate running compensation (a variable to accumulate small errors)."

For example, instead of

double sum = 0.0;
for( unsigned int i = 0; i < array.Size(); ++i )
  {
  sum += array.GetElement(i);
  }

do

typedef CompensatedSummation<double> CompensatedSummationType;
CompensatedSummationType compensatedSummation;
for( unsigned int i = 0; i < array.Size(); ++i )
  {
  compensatedSummation += array.GetElement(i);
  }
double sum = compensatedSummation.GetSum();

Definition at line 66 of file itkCompensatedSummation.h.

Public Types
typedef NumericTraits < FloatType >::AccumulateType	AccumulateType
typedef TFloat	FloatType
typedef CompensatedSummation	Self

Public Member Functions
	CompensatedSummation ()
	CompensatedSummation (const Self &rhs)
const AccumulateType &	GetSum () const
Self &	operator-= (const FloatType &rhs)
Self &	operator= (const Self &rhs)
Self &	operator= (const FloatType &rhs)
void	ResetToZero ()
void	AddElement (const FloatType &element)
Self &	operator+= (const FloatType &rhs)
Self &	operator*= (const FloatType &rhs)
Self &	operator/= (const FloatType &rhs)

Private Member Functions
	typedef (itk::Concept::IsFloatingPoint< TFloat >) OnlyDefinedForFloatingPointTypes

Private Attributes
AccumulateType	m_Compensation
AccumulateType	m_Sum

Member Typedef Documentation

template<class TFloat >

typedef NumericTraits< FloatType >::AccumulateType itk::CompensatedSummation< TFloat >::AccumulateType

Type used for the sum and compensation.

Definition at line 73 of file itkCompensatedSummation.h.

template<class TFloat >

typedef TFloat itk::CompensatedSummation< TFloat >::FloatType

Type of the input elements.

Definition at line 70 of file itkCompensatedSummation.h.

template<class TFloat >

typedef CompensatedSummation itk::CompensatedSummation< TFloat >::Self

Standard class typedefs.

Definition at line 76 of file itkCompensatedSummation.h.

Constructor & Destructor Documentation

template<class TFloat >

itk::CompensatedSummation< TFloat >::CompensatedSummation

(

)

Constructor.

template<class TFloat >

itk::CompensatedSummation< TFloat >::CompensatedSummation

(

const Self &

rhs

)

Copy constructor.

Member Function Documentation

template<class TFloat >

void itk::CompensatedSummation< TFloat >::AddElement

(

const FloatType &

element

)

Add an element to the sum.

template<class TFloat >

const AccumulateType& itk::CompensatedSummation< TFloat >::GetSum

(

)

const

Get the sum.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator*=

(

const FloatType &

rhs

)

Division and multiplication. These do not provide any numerical advantages relative to vanilla division and multiplication.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator+=

(

const FloatType &

rhs

)

Add an element to the sum.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator-=

(

const FloatType &

rhs

)

Subtract an element from the sum.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator/=

(

const FloatType &

rhs

)

Division and multiplication. These do not provide any numerical advantages relative to vanilla division and multiplication.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator=

(

const Self &

rhs

)

Assignment operator.

template<class TFloat >

Self& itk::CompensatedSummation< TFloat >::operator=

(

const FloatType &

rhs

)

Reset the sum to the given value and the compensation to zero.

template<class TFloat >

void itk::CompensatedSummation< TFloat >::ResetToZero

(

)

Reset the sum and compensation to zero.

template<class TFloat >

itk::CompensatedSummation< TFloat >::typedef ( itk::Concept::IsFloatingPoint< TFloat >  )

private

This class requires OnlyDefinedForFloatingPointTypes in the form of ( itk::Concept::IsFloatingPoint< TFloat > )

Member Data Documentation

template<class TFloat >

AccumulateType itk::CompensatedSummation< TFloat >::m_Compensation

private

Definition at line 112 of file itkCompensatedSummation.h.

template<class TFloat >

AccumulateType itk::CompensatedSummation< TFloat >::m_Sum

private

Definition at line 111 of file itkCompensatedSummation.h.

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

• itkCompensatedSummation.h