DirectGraphicalModels::CPowell Class Reference

The Powell search method class. More...

#include <Powell.h>

Public Member Functions
	CPowell (word nParams)
	Constructor. More...
	~CPowell (void)
void	reset (void)
	Resets class variables. More...
void	setInitParams (float *pParam)
	Sets the initial parameters (arguments) for the search algorithm. More...
void	setDeltas (float *pDelta)
	Sets the searching steps along the parameters (arguments) More...
void	setMinParams (float *pMinParam)
	Sets the lower boundary for parameters (arguments) search. More...
void	setMaxParams (float *pMaxParam)
	Sets the upper boundary for parameters (arguments) search. More...
void	setAcceleration (float acceleration)
	Sets the acceleration coefficient. More...
float *	getParams (float val)
	Gets the updated parameters (arguments) More...
bool	isConverged (void)
	Indicates weather the method has converged. More...

Detailed Description

The Powell search method class.

The Powell search method is an iterative optimisation algortihm that does not require an estimate for the gradient of the objective function: \( f:\mathbb{R}^n\rightarrow\mathbb{R} \), where \( n \) is the number of parameters (arguments). In order to find the extremum point, one may use the common case:

using namespace DirectGraphicalModels;

const word nParams = 2;

float   * pParam;
float     initParam[nParams] = {0.0f, 0.0f};        // coordinates of the initial point for the search algorithm
float     initDelta[nParams] = {0.1f, 0.1f};        // searching steps along the parameters (arguments)

CPowell *powell = new CPowell(nParams);
powell->setInitParams(initParam);
powell->setDeltas(initDelta);

pParam = initParam;

while(!powell->isConverged()) {
    float val = objectiveFunction(pParam);      
    pParam = powell->getParams(val);
} 

Author

Sergey G. Kosov, serge.nosp@m.y.ko.nosp@m.sov@p.nosp@m.roje.nosp@m.ct-10.nosp@m..de

Definition at line 39 of file Powell.h.

Constructor & Destructor Documentation

DirectGraphicalModels::CPowell::CPowell

(

word

nParams

)

Constructor.

Parameters

nParams

Number of parameters (arguments) of the objective function

Definition at line 7 of file Powell.cpp.

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DirectGraphicalModels::CPowell::~CPowell

(

void

)

Definition at line 19 of file Powell.cpp.

Member Function Documentation

float * DirectGraphicalModels::CPowell::getParams

(

float

val

)

Gets the updated parameters (arguments)

This function updates the parameters (arguments) of the objective function based on its outcome value val and retunrs them (See example code for more details)

Parameters

val	The current value of the objective function

Returns

The pointer to array with the updated parameters

Definition at line 78 of file Powell.cpp.

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bool DirectGraphicalModels::CPowell::isConverged

(

void

)

Indicates weather the method has converged.

Return values

true	if the method has converged
false	otherwise

Definition at line 168 of file Powell.cpp.

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void DirectGraphicalModels::CPowell::reset

(

void

)

Resets class variables.

Definition at line 23 of file Powell.cpp.

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void DirectGraphicalModels::CPowell::setAcceleration

(

float

acceleration

)

Sets the acceleration coefficient.

Incrasing this parameter may speed-up the convergence of the method, however too large values may affect the calculation stability

Default value is 0.1

Parameters

acceleration

The acceleration coefficient

Definition at line 72 of file Powell.cpp.

void DirectGraphicalModels::CPowell::setDeltas

(

float *

pDelta

)

Sets the searching steps along the parameters (arguments)

Default values are 0.1 for all parameters (arguments)

Parameters

pDelta

Pointer to an array with the offset values for each parameter (argument)

Definition at line 67 of file Powell.cpp.

void DirectGraphicalModels::CPowell::setInitParams

(

float *

pParam

)

Sets the initial parameters (arguments) for the search algorithm.

Default values are 0 for all parameters (arguments)

Parameters

pParam

Pointer to an array with the initial values for the search algorithm

Definition at line 38 of file Powell.cpp.

void DirectGraphicalModels::CPowell::setMaxParams

(

float *

pMaxParam

)

Sets the upper boundary for parameters (arguments) search.

Default values are \(+\infty\) for all parameters (arguments)

Parameters

pMaxParam

Pointer to an array with the maximal parameter (argument) values

Definition at line 60 of file Powell.cpp.

void DirectGraphicalModels::CPowell::setMinParams

(

float *

pMinParam

)

Sets the lower boundary for parameters (arguments) search.

Default values are \(-\infty\) for all parameters (arguments)

Parameters

pMinParam

Pointer to an array with the minimal parameter (argument) values

Definition at line 53 of file Powell.cpp.

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

• D:/Projects/DGM/modules/DGM/Powell.h
• D:/Projects/DGM/modules/DGM/Powell.cpp