#include <itkNormalVariateGenerator.h>

Inheritance diagram for itk::Statistics::NormalVariateGenerator:

Collaboration diagram for itk::Statistics::NormalVariateGenerator:

Detailed Description

Normal random variate generator.

This generation method was initially developed and implemented by Martin Styner, University of North Carolina at Chapel Hill, and his colleagues.

You should run Initialize() function before call GetNormalVariate() function.

The followings are original comments.

Revision date 31 May 1996 This is a revised version of the algorithm described in

ACM Transactions on Mathematical Software, Vol 22, No 1 March 1996, pp 119-127.

It is somewhat faster, and uses less memory as the vector of variates is updated in-situ. It has passed all the same statistical tests as described in the TOMS article, plus others. Seems OK so far.

   Works well with total pool of 1024 variates, and does not need
   two vectors of this size, so does less damage to cache.
           Has been tested for frequency of tail values which
   should occur once in a million. OK. Other usual tests OK.
   About 13 % faster than TOMS version.

   FAST GENERATOR OF PSEUDO-RANDOM UNIT NORMAL VARIATES

           C.S.Wallace, Monash University, 1994

To use this code, files needing to call the generator should include:

#include "FastNorm.h"

and be linked with the maths library (-lm) FastNorm.h contains declaration of the initialization routine 'initnorm()', definition of a macro 'FastGauss' used to generate variates, and three variables used in the macro. Read below for calling conventions.

THIS CODE ASSUMES TWO'S-COMPLEMENT 32-BIT INTEGER ARITHMATIC. IT ALSO ASSUMES THE 'C' COMPILER COMPILES THE LEFT-SHIFT OPERATOR "<<" AS A LOGICAL SHIFT, DISCARDING THE SIGN DIGIT AND SHIFTING IN ZEROS ON THE RIGHT, SO " X << 1" IS EQUIVALENT TO " X+X ". IT ALSO ASSUMES THE RIGHT-SHIFT OPERATOR ">>" IS SIGN-PRESERVING, SO ( -2 >> 1) = -1, ( -1>>1) = -1.

    A fast generator of pseudo-random variates from the unit Normal

distribution. It keeps a pool of about 1000 variates, and generates new ones by picking 4 from the pool, rotating the 4-vector with these as its components, and replacing the old variates with the components of the rotated vector.

    The program should initialize the generator by calling

initnorm(seed) with seed a int integer seed value. Different seed values will give different sequences of Normals. Then, wherever the program needs a new Normal variate, it should use the macro FastGauss, e.g. in statements like: x = FastGauss; (Sets x to a random Normal value)

Definition at line 97 of file itkNormalVariateGenerator.h.

Public Types
typedef SmartPointer< const Self >	ConstPointer

typedef SmartPointer< Self >	Pointer

typedef NormalVariateGenerator	Self

typedef RandomVariateGeneratorBase	Superclass

Public Types inherited from itk::Statistics::RandomVariateGeneratorBase
typedef SmartPointer< const Self >	ConstPointer

typedef SmartPointer< Self >	Pointer

typedef RandomVariateGeneratorBase	Self

typedef Object	Superclass

Public Types inherited from itk::Object
typedef SmartPointer< const Self >	ConstPointer

typedef SmartPointer< Self >	Pointer

typedef Object	Self

typedef LightObject	Superclass

Public Types inherited from itk::LightObject
typedef SmartPointer< const Self >	ConstPointer

typedef SmartPointer< Self >	Pointer

typedef LightObject	Self

Public Member Functions
virtual ::itk::LightObject::Pointer	CreateAnother (void) const

virtual const char *	GetNameOfClass () const

double	GetVariate ()

void	Initialize (int randomSeed)

Static Public Member Functions
static Pointer	New ()

Protected Member Functions
double	FastNorm (void)

	NormalVariateGenerator ()

virtual void	PrintSelf (std::ostream &os, Indent indent) const

virtual	~NormalVariateGenerator ()

Protected Member Functions inherited from itk::Statistics::RandomVariateGeneratorBase
	RandomVariateGeneratorBase ()

virtual	~RandomVariateGeneratorBase ()

Protected Member Functions inherited from itk::Object
	Object ()

bool	PrintObservers (std::ostream &os, Indent indent) const

virtual void	SetTimeStamp (const TimeStamp &time)

virtual	~Object ()

Protected Member Functions inherited from itk::LightObject
virtual LightObject::Pointer	InternalClone () const

	LightObject ()

virtual void	PrintHeader (std::ostream &os, Indent indent) const

virtual void	PrintTrailer (std::ostream &os, Indent indent) const

virtual	~LightObject ()

Private Attributes
double	m_ActualRSD

double	m_Chic1

double	m_Chic2

int	m_ELEN

int	m_Gaussfaze

int *	m_Gausssave

double	m_GScale

int	m_Irs

int	m_LEN

int	m_LMASK

int	m_Lseed

int	m_Nslew

double	m_Rcons

double	m_Rscale

double	m_Scale

int	m_TLEN

int *	m_Vec1

Additional Inherited Members
Protected Types inherited from itk::LightObject
typedef int	InternalReferenceCountType

Protected Attributes inherited from itk::LightObject
InternalReferenceCountType	m_ReferenceCount

SimpleFastMutexLock	m_ReferenceCountLock

Member Typedef Documentation

typedef SmartPointer< const Self > itk::Statistics::NormalVariateGenerator::ConstPointer

Definition at line 105 of file itkNormalVariateGenerator.h.

typedef SmartPointer< Self > itk::Statistics::NormalVariateGenerator::Pointer

Definition at line 104 of file itkNormalVariateGenerator.h.

typedef NormalVariateGenerator itk::Statistics::NormalVariateGenerator::Self

Standard class typedefs.

Definition at line 102 of file itkNormalVariateGenerator.h.

typedef RandomVariateGeneratorBase itk::Statistics::NormalVariateGenerator::Superclass

Definition at line 103 of file itkNormalVariateGenerator.h.

Constructor & Destructor Documentation

itk::Statistics::NormalVariateGenerator::NormalVariateGenerator ( )

protected

virtual itk::Statistics::NormalVariateGenerator::~NormalVariateGenerator ( )

protectedvirtual

Member Function Documentation

virtual::itk::LightObject::Pointer itk::Statistics::NormalVariateGenerator::CreateAnother ( void ) const

virtual

Create an object from an instance, potentially deferring to a factory. This method allows you to create an instance of an object that is exactly the same type as the referring object. This is useful in cases where an object has been cast back to a base class.

Reimplemented from itk::Object.

double itk::Statistics::NormalVariateGenerator::FastNorm ( void )

protected

get a variate

virtual const char* itk::Statistics::NormalVariateGenerator::GetNameOfClass ( ) const

virtual

Run-time type information (and related methods).

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

double itk::Statistics::NormalVariateGenerator::GetVariate ( )

virtual

get a variate using FastNorm function

Implements itk::Statistics::RandomVariateGeneratorBase.

void itk::Statistics::NormalVariateGenerator::Initialize ( int randomSeed )

generate random number table

static Pointer itk::Statistics::NormalVariateGenerator::New ( )

static

Method for creation through the object factory.

virtual void itk::Statistics::NormalVariateGenerator::PrintSelf	(	std::ostream &	os,
		Indent	indent
	)		const

protectedvirtual

Methods invoked by Print() to print information about the object including superclasses. Typically not called by the user (use Print() instead) but used in the hierarchical print process to combine the output of several classes.

Reimplemented from itk::Object.