[Insight-users] SetNumberOfSpatialSamples has no effect on computation time???

[pinpress]

Hi Luis,

Thanks for the reply. Please see below for my answers.


Hi  Pinpress,

Thanks for your clarification.

---

A change from 10% of samples to 100% of samples should be
noticeable in the time that it takes to compute the registration.


A)  How big are your images ?
> My images are typically 256-by-256-by-120, or that range. 

B)  How many pixels do they have ?
>  About 8 million voxels/pixels each, for both fixed and moving images. 


C)  How many iterations did your optimizer ran ?
> I set the maximum iterations to be 200, but the program will stop if other
> convergence criterion is met (e.g., 

D)  What Transform are you using ?

> I used the following in the code: 

#include "itkVersorRigid3DTransform.h"
#include "itkCenteredTransformInitializer.h"

#include "itkVersorRigid3DTransformOptimizer.h"



something else might be at play here....

> Not sure why. But if I simply change the similarity metric to Mattes and
> keep everything else the same, then the difference in computational cost
> is obvious. Another thing to note is that the Mattes MI metric is
> multi-threaded, so I was able to use all 8 CPUs, whereas other metrics are
> not multi-threaded. Therefore I was only able to use one CPU. Regardless,
> if I choose only to use 1 CPU for Mattes MI metric, the # of spatial
> samples still play a role in computational cost. 

> Thanks for looking into this!

     Luis


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