ITK: itk::Statistics::NormalVariateGenerator Class Reference

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

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

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 decribed 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.

To use this code, files needing to call the generator should include the file "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)

Member Typedef Documentation

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

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

Definition at line 99 of file itkNormalVariateGenerator.h.

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

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

Definition at line 98 of file itkNormalVariateGenerator.h.

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

Standard class typedefs.

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

Definition at line 96 of file itkNormalVariateGenerator.h.

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

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

Definition at line 97 of file itkNormalVariateGenerator.h.

Constructor & Destructor Documentation

itk::Statistics::NormalVariateGenerator::NormalVariateGenerator ( ) [protected]

virtual itk::Statistics::NormalVariateGenerator::~NormalVariateGenerator ( ) [protected, virtual]

Member Function Documentation

unsigned long itk::Object::AddObserver	(	const EventObject &	event,
		Command *
	)			const `[inherited]`

unsigned long itk::Object::AddObserver	(	const EventObject &	event,
		Command *
	)			`[inherited]`

Allow people to add/remove/invoke observers (callbacks) to any ITK object. This is an implementation of the subject/observer design pattern. An observer is added by specifying an event to respond to and an itk::Command to execute. It returns an unsigned long tag which can be used later to remove the event or retrieve the command. The memory for the Command becomes the responsibility of this object, so don't pass the same instance of a command to two different objects

static void itk::LightObject::BreakOnError ( ) [static, inherited]

This method is called when itkExceptionMacro executes. It allows the debugger to break on error.

virtual LightObject::Pointer itk::Object::CreateAnother ( ) const [virtual, inherited]

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::LightObject.

virtual void itk::Object::DebugOff ( ) const [virtual, inherited]

Turn debugging output off.

virtual void itk::Object::DebugOn ( ) const [virtual, inherited]

Turn debugging output on.

virtual void itk::LightObject::Delete ( ) [virtual, inherited]

Delete an itk object. This method should always be used to delete an object when the new operator was used to create it. Using the C delete method will not work with reference counting.

double itk::Statistics::NormalVariateGenerator::FastNorm ( void ) [protected]

get a variate

Command* itk::Object::GetCommand ( unsigned long tag ) [inherited]

Get the command associated with the given tag. NOTE: This returns a pointer to a Command, but it is safe to asign this to a Command::Pointer. Since Command inherits from LightObject, at this point in the code, only a pointer or a reference to the Command can be used.

bool itk::Object::GetDebug ( ) const [inherited]

Get the value of the debug flag.

static bool itk::Object::GetGlobalWarningDisplay ( ) [static, inherited]

const MetaDataDictionary& itk::Object::GetMetaDataDictionary ( void ) const [inherited]

Returns:: A constant reference to this objects MetaDataDictionary.

MetaDataDictionary& itk::Object::GetMetaDataDictionary ( void ) [inherited]

Returns:: A reference to this objects MetaDataDictionary.

Warning:: This reference may be changed.

virtual unsigned long itk::Object::GetMTime ( ) const [virtual, inherited]

Return this objects modified time.

Referenced by itk::SpatialObject< ::itk::GetMeshDimension< TMesh >::PointDimension >::GetObjectMTime().

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

Run-time type information (and related methods).

Reimplemented from itk::Statistics::RandomVariateGeneratorBase.

virtual int itk::LightObject::GetReferenceCount ( ) const [inline, virtual, inherited]

Gets the reference count on this object.

Definition at line 98 of file itkLightObject.h.

double itk::Statistics::NormalVariateGenerator::GetVariate ( ) [virtual]

get a variate using FastNorm function

Implements itk::Statistics::RandomVariateGeneratorBase.

static void itk::Object::GlobalWarningDisplayOff ( ) [inline, static, inherited]

Definition at line 100 of file itkObject.h.

References itk::Object::SetGlobalWarningDisplay().

static void itk::Object::GlobalWarningDisplayOn ( ) [inline, static, inherited]

Definition at line 98 of file itkObject.h.

References itk::Object::SetGlobalWarningDisplay().

bool itk::Object::HasObserver ( const EventObject & event ) const [inherited]

Return true if an observer is registered for this event.

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

generate random number table

void itk::Object::InvokeEvent ( const EventObject & ) const [inherited]

Call Execute on all the Commands observing this event id. The actions triggered by this call doesn't modify this object.

void itk::Object::InvokeEvent ( const EventObject & ) [inherited]

Call Execute on all the Commands observing this event id.

virtual void itk::Object::Modified ( ) const [virtual, inherited]

Update the modification time for this object. Many filters rely on the modification time to determine if they need to recompute their data.

Referenced by itk::NarrowBandImageFilterBase< TInputImage, itk::Image< TOutputPixelType,::itk::GetImageDimension< TInputImage >::ImageDimension > >::InsertNarrowBandNode(), itk::MatrixOffsetTransformBase< TScalarType, 3, 3 >::SetCenter(), itk::HistogramAlgorithmBase< TInputHistogram >::SetInputHistogram(), itk::MatrixOffsetTransformBase< TScalarType, 3, 3 >::SetMatrix(), itk::NarrowBandImageFilterBase< TInputImage, itk::Image< TOutputPixelType,::itk::GetImageDimension< TInputImage >::ImageDimension > >::SetNarrowBand(), itk::NarrowBandImageFilterBase< TInputImage, itk::Image< TOutputPixelType,::itk::GetImageDimension< TInputImage >::ImageDimension > >::SetNarrowBandInnerRadius(), itk::NarrowBandImageFilterBase< TInputImage, itk::Image< TOutputPixelType,::itk::GetImageDimension< TInputImage >::ImageDimension > >::SetNarrowBandTotalRadius(), itk::MatrixOffsetTransformBase< TScalarType, 3, 3 >::SetOffset(), itk::ThresholdLabelerImageFilter< TInputImage, TOutputImage >::SetRealThresholds(), itk::CollidingFrontsImageFilter< TInputImage, TOutputImage >::SetSeedPoints1(), itk::CollidingFrontsImageFilter< TInputImage, TOutputImage >::SetSeedPoints2(), itk::NonUniformBSpline< TDimension >::SetSplineOrder(), itk::ThresholdLabelerImageFilter< TInputImage, TOutputImage >::SetThresholds(), itk::Statistics::GoodnessOfFitFunctionBase< TInputHistogram >::SetTotalObservedScale(), and itk::MatrixOffsetTransformBase< TScalarType, 3, 3 >::SetTranslation().

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

Method for creation through the object factory.

Reimplemented from itk::Object.

void itk::LightObject::Print	(	std::ostream &	os,
		Indent	indent = `0`
	)			const `[inherited]`

Cause the object to print itself out.

Referenced by itk::WeakPointer< itk::ProcessObject >::Print().

virtual void itk::LightObject::PrintHeader	(	std::ostream &	os,
		Indent	indent
	)			const `[protected, virtual, inherited]`

bool itk::Object::PrintObservers	(	std::ostream &	os,
		Indent	indent
	)			const `[protected, inherited]`

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

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.

virtual void itk::LightObject::PrintTrailer	(	std::ostream &	os,
		Indent	indent
	)			const `[protected, virtual, inherited]`

virtual void itk::Object::Register ( ) const [virtual, inherited]

Increase the reference count (mark as used by another object).

Reimplemented from itk::LightObject.

void itk::Object::RemoveAllObservers ( ) [inherited]

Remove all observers .

void itk::Object::RemoveObserver ( unsigned long tag ) [inherited]

Remove the observer with this tag value.

void itk::Object::SetDebug ( bool debugFlag ) const [inherited]

Set the value of the debug flag. A non-zero value turns debugging on.

static void itk::Object::SetGlobalWarningDisplay ( bool flag ) [static, inherited]

This is a global flag that controls whether any debug, warning or error messages are displayed.

Referenced by itk::Object::GlobalWarningDisplayOff(), and itk::Object::GlobalWarningDisplayOn().

void itk::Object::SetMetaDataDictionary ( const MetaDataDictionary & rhs ) [inherited]

Returns:: Set the MetaDataDictionary

virtual void itk::Object::SetReferenceCount ( int ) [virtual, inherited]

Sets the reference count (use with care)

Reimplemented from itk::LightObject.

virtual void itk::Object::UnRegister ( ) const [virtual, inherited]

Decrease the reference count (release by another object).

Reimplemented from itk::LightObject.

Member Data Documentation

volatile int itk::LightObject::m_ReferenceCount [mutable, protected, inherited]

Number of uses of this object by other objects.

Definition at line 119 of file itkLightObject.h.

SimpleFastMutexLock itk::LightObject::m_ReferenceCountLock [mutable, protected, inherited]

Mutex lock to protect modification to the reference count

Definition at line 122 of file itkLightObject.h.

itk::Statistics::NormalVariateGenerator Class Reference

Detailed Description

Public Types

Public Member Functions

Static Public Member Functions

Protected Member Functions

Protected Attributes

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation


Public Types
typedef SmartPointer< const Self >	ConstPointer
typedef SmartPointer< Self >	Pointer
typedef NormalVariateGenerator	Self
typedef RandomVariateGeneratorBase	Superclass
Public Member Functions
virtual LightObject::Pointer	CreateAnother () const
virtual void	DebugOff () const
virtual void	DebugOn () const
virtual void	Delete ()
Command *	GetCommand (unsigned long tag)
bool	GetDebug () const
const MetaDataDictionary &	GetMetaDataDictionary (void) const
MetaDataDictionary &	GetMetaDataDictionary (void)
virtual unsigned long	GetMTime () const
virtual const char *	GetNameOfClass () const
virtual int	GetReferenceCount () const
double	GetVariate ()
bool	HasObserver (const EventObject &event) const
void	Initialize (int randomSeed)
void	InvokeEvent (const EventObject &) const
void	InvokeEvent (const EventObject &)
virtual void	Modified () const
void	Print (std::ostream &os, Indent indent=0) const
virtual void	Register () const
void	RemoveAllObservers ()
void	RemoveObserver (unsigned long tag)
void	SetDebug (bool debugFlag) const
void	SetMetaDataDictionary (const MetaDataDictionary &rhs)
virtual void	SetReferenceCount (int)
virtual void	UnRegister () const

unsigned long	AddObserver (const EventObject &event, Command *) const
unsigned long	AddObserver (const EventObject &event, Command *)
Static Public Member Functions
static void	BreakOnError ()
static Pointer	New ()

static bool	GetGlobalWarningDisplay ()
static void	GlobalWarningDisplayOff ()
static void	GlobalWarningDisplayOn ()
static void	SetGlobalWarningDisplay (bool flag)
Protected Member Functions
double	FastNorm (void)
	NormalVariateGenerator ()
bool	PrintObservers (std::ostream &os, Indent indent) const
virtual void	PrintSelf (std::ostream &os, Indent indent) const
virtual	~NormalVariateGenerator ()

virtual void	PrintHeader (std::ostream &os, Indent indent) const
virtual void	PrintTrailer (std::ostream &os, Indent indent) const
Protected Attributes
volatile int	m_ReferenceCount
SimpleFastMutexLock	m_ReferenceCountLock