1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/*=========================================================================
*
* Copyright Insight Software Consortium
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#include "itkPowellOptimizer.h"
int POWELL_CALLS_TO_GET_VALUE = 0;
/**
* The objectif function is the quadratic form:
*
* 1/2 x^T A x - b^T x
*
* Where A is a matrix and b is a vector
* The system in this example is:
*
* | 3 2 ||x| | 2| |0|
* | 2 6 ||y| + |-8| = |0|
*
*
* the solution is the vector | 2 -2 |
* \class PowellBoundedCostFunction
*
*/
class PowellBoundedCostFunction : public itk::SingleValuedCostFunction
{
public:
typedef PowellBoundedCostFunction Self;
typedef itk::SingleValuedCostFunction Superclass;
typedef itk::SmartPointer<Self> Pointer;
typedef itk::SmartPointer<const Self> ConstPointer;
itkNewMacro( Self );
itkTypeMacro( PowellBoundedCostFunction, SingleValuedCostFunction );
enum { SpaceDimension=2 };
typedef Superclass::ParametersType ParametersType;
typedef Superclass::DerivativeType DerivativeType;
typedef Superclass::MeasureType MeasureType;
PowellBoundedCostFunction()
{
}
void GetDerivative( const ParametersType & ,
DerivativeType & ) const ITK_OVERRIDE
{
}
virtual MeasureType GetValue( const ParametersType & parameters ) const ITK_OVERRIDE
{
++POWELL_CALLS_TO_GET_VALUE;
double x = parameters[0];
double y = parameters[1];
std::cout << " GetValue( ";
std::cout << x << " ";
std::cout << y << ") = ";
MeasureType measure = 0.5*(3*x*x+4*x*y+6*y*y) - 2*x + 8*y;
std::cout << measure << std::endl;
return measure;
}
virtual unsigned int GetNumberOfParameters(void) const ITK_OVERRIDE
{
return SpaceDimension;
}
private:
};
int itkPowellOptimizerTest(int, char* [] )
{
std::cout << "Powell Optimizer Test ";
std::cout << std::endl << std::endl;
typedef itk::PowellOptimizer OptimizerType;
// Declaration of a itkOptimizer
OptimizerType::Pointer itkOptimizer = OptimizerType::New();
// Declaration of the CostFunction
PowellBoundedCostFunction::Pointer costFunction = PowellBoundedCostFunction::New();
itkOptimizer->SetCostFunction( costFunction.GetPointer() );
typedef PowellBoundedCostFunction::ParametersType ParametersType;
const unsigned int spaceDimension =
costFunction->GetNumberOfParameters();
// We start not so far from | 2 -2 |
ParametersType initialPosition( spaceDimension );
initialPosition[0] = 100;
initialPosition[1] = -100;
itkOptimizer->SetMaximize(false);
itkOptimizer->SetStepLength( 10 );
itkOptimizer->SetStepTolerance( 0.01 );
itkOptimizer->SetValueTolerance( 0.1 );
itkOptimizer->SetMaximumIteration( 100 );
itkOptimizer->SetInitialPosition( initialPosition );
try
{
itkOptimizer->StartOptimization();
}
catch( itk::ExceptionObject & e )
{
std::cout << "Exception thrown ! " << std::endl;
std::cout << "An error occurred during Optimization" << std::endl;
std::cout << "Location = " << e.GetLocation() << std::endl;
std::cout << "Description = " << e.GetDescription() << std::endl;
return EXIT_FAILURE;
}
ParametersType finalPosition = itkOptimizer->GetCurrentPosition();
std::cout << "Solution = (";
std::cout << finalPosition[0] << ",";
std::cout << finalPosition[1] << ")" << std::endl;
//
// check results to see if it is within range
//
bool pass = true;
double trueParameters[2] = { 2, -2 };
for( unsigned int j = 0; j < 2; j++ )
{
if( itk::Math::abs( finalPosition[j] - trueParameters[j] ) > 0.01 )
pass = false;
}
// Exercise various member functions.
std::cout << "Maximize: " << itkOptimizer->GetMaximize() << std::endl;
std::cout << "StepLength: " << itkOptimizer->GetStepLength();
std::cout << std::endl;
std::cout << "CurrentIteration: " << itkOptimizer->GetCurrentIteration();
std::cout << std::endl;
itkOptimizer->Print( std::cout );
std::cout << "Calls to GetValue = " << POWELL_CALLS_TO_GET_VALUE << std::endl;
if( !pass )
{
std::cout << "Test failed." << std::endl;
return EXIT_FAILURE;
}
std::cout << "Test passed." << std::endl;
return EXIT_SUCCESS;
}
|
