ITK
4.3.0
Insight Segmentation and Registration Toolkit
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#include <itkNormalVariateGenerator.h>
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:
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 |
typedef SmartPointer< const Self > itk::Statistics::NormalVariateGenerator::ConstPointer |
Definition at line 105 of file itkNormalVariateGenerator.h.
Definition at line 104 of file itkNormalVariateGenerator.h.
Standard class typedefs.
Definition at line 102 of file itkNormalVariateGenerator.h.
Definition at line 103 of file itkNormalVariateGenerator.h.
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protectedvirtual |
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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.
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get a variate
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Run-time type information (and related methods).
Reimplemented from itk::Statistics::RandomVariateGeneratorBase.
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get a variate using FastNorm function
Implements itk::Statistics::RandomVariateGeneratorBase.
void itk::Statistics::NormalVariateGenerator::Initialize | ( | int | randomSeed | ) |
generate random number table
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Method for creation through the object factory.
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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.
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Definition at line 148 of file itkNormalVariateGenerator.h.
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Definition at line 146 of file itkNormalVariateGenerator.h.
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Definition at line 147 of file itkNormalVariateGenerator.h.
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Definition at line 132 of file itkNormalVariateGenerator.h.
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Definition at line 137 of file itkNormalVariateGenerator.h.
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Definition at line 138 of file itkNormalVariateGenerator.h.
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Definition at line 140 of file itkNormalVariateGenerator.h.
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Definition at line 144 of file itkNormalVariateGenerator.h.
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Definition at line 133 of file itkNormalVariateGenerator.h.
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Definition at line 134 of file itkNormalVariateGenerator.h.
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Definition at line 145 of file itkNormalVariateGenerator.h.
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Definition at line 143 of file itkNormalVariateGenerator.h.
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Definition at line 131 of file itkNormalVariateGenerator.h.
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Definition at line 130 of file itkNormalVariateGenerator.h.
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Definition at line 129 of file itkNormalVariateGenerator.h.
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Definition at line 135 of file itkNormalVariateGenerator.h.
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Definition at line 142 of file itkNormalVariateGenerator.h.