[Insight-users] Re: SetMaxIterations(0) still computes

[Emma Ryan]

Hi,

   With reference to my earlier email ( below), I think ITK does not allow the MaxNumberOfIterations to be zero.  It needs to be a minimum of one because the check 
if (m_currentIteration = = m_NumberOfIterations) then quit; is done in a sort-of 'do-while' loop rather than 'while'. So this condition is never true for m_NumberofIterations=0.

I am still confused about Stop_Condition getting a value of 5.

Also, if Stop_Condition is defined by NumberofIterations, then why doesn't the optimizer continue iterating till it reaches the number, rather than terminating at a 'decent' metric value ?

Obviously there is another hidden condition for termination which I dont see.  Could anyone point to me the location ?

Thank you,
Emma

----- Original Message ----
From: Emma Ryan <eryanvtk at yahoo.com>
To: insight-users at itk.org
Sent: Thursday, August 9, 2007 1:35:23 AM
Subject: SetMaxIterations(0) still computes

Hi,

  I'm trying to debug my rigid registration program and the first step is to reduce the number of iterations.
So I set it to 0, but when I execute my program it still shows me several iterations.  Any clue as to why this might be happening ?

Here is the output of the optimizer (segment 1).  As you can see, NumberOfIterations = 0 . The StopCondition which I thought would be 0 is 5. So based on this and other experiments, I have a few questions.

1. Shouldn't the StopCondition be 0 ?
2. If optimizer->SetNumberOfIterations(0), then what do the following iterations represent  and where do they come from ?
3. Also, it I set the NumberOfIterations to some otehr number such as 100000, it still performs 500 iterations (the default value from
 the example programs)
4. The Mean Square error metric that I compute on Binarized input images is the same as that computed on grayscale images. So what I am doing here is that I convert the grayscale images to binary. ie. Every tissue, except bone is black. Then I use these binary images for registration. The metric value returned by the registration process is compared against the metric value obtained by applying the same transform on original grayscale images and checking the mean squared error. Surprisingly these two values are EXACTLY the same. I expect them to be different for obvious reasons.
The way I compute the metric on the original grayscale images is shown below under segment 2


What is going on ?

Any clue ?

Thanks in advance
Emma


SEGMENT 1
---------------
VersorRigid3DTransformOptimizer (019220B8)
  RTTI typeinfo:   class itk::VersorRigid3DTransformOptimizer
 
 Reference Count: 2
  Modified Time: 874
  Debug: Off
  Observers:
    none
  InitialPosition: []
  CurrentPosition: []
  Scales: [1, 1, 1, 0.001, 0.001, 0.001]
  MaximumStepLength: 0.2
  MinimumStepLength: 0.001
  RelaxationFactor: 0.5
  GradientMagnitudeTolerance: 0.1
  NumberOfIterations: 0
  CurrentIteration: 0
  Value: 0
  Maximize: 0
  CostFunction: (None)
  CurrentStepLength: 0
  StopCondition: 5
  Gradient: []
0   1976.47   [0.000460224, -0.0157202, -0.041473, -6.58714, -9.17326, 0.231981]

1   669.48   [0.00152886, 0.00402301, -0.0345613, -6.60421, -9.36806, 0.229234]
2   576.079   [-0.000710302, -0.0100887, -0.0583703, -6.5576, -9.55443, 0.227974
]
3   895.329   [0.0024751, 0.017149,
 -0.0188799, -6.6526, -9.70157, 0.236332]
4   1454.49   [0.000779181, 0.00262768, -0.0415692, -6.57818, -9.73974, 0.226865
]
5   208.619   [-0.000462126, -0.00352645, -0.0488536, -6.56913, -9.83714, 0.2190
21]
6   320.494   [0.00156166, 0.00864248, -0.0314357, -6.61138, -9.91627, 0.207684]

7   724.278   [0.000322199, -0.00121238, -0.0455856, -6.58293, -9.93788, 0.20247
4]
8   143.422   [0.000259716, 0.00266556, -0.0399937, -6.59857, -9.98223, 0.192322
]
9   223.3   [-0.000310048, -0.004876, -0.0507685, -6.57875, -10.018, 0.180773]
10   419.74   [0.00029441, 5.14277e-005, -0.0436893, -6.59453, -10.026, 0.177275
]
1
.......




SEGMENT 2

MetricType::Pointer         metricOrig   
        = MetricType::New();    

        metricOrig->SetInterpolator(interpolator);
        metricOrig->SetTransform(transform);
        metricOrig->SetFixedImage(fixedImageReaderOrig->GetOutput());
        metricOrig->SetMovingImage(movingImageReaderOrig->GetOutput());
        metricOrig->SetTransformParameters(finalParameters);    
        MetricType::TransformParametersType finalParam = registration->GetLastTransformParameters();
        
        std::cout<<" MetricOnOriginalImage = "<<metric->GetValue(finalParam)<<std::endl;









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