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

[pinpress]

Hi Luis,

Thanks for the reply. Yes, I was sure that I compiled in Release mode, and I
have set the two Cmake Flags so that to use optimized registration
techniques. The "SetNumberOfSpatialSamples ()" function does have a very
noticeable effect on the performance on Mattes Registration technique. I
have timed the registration (using "time" in Linux) using normalized mutual
information or correlation coefficient image similarity metrics to perform
the registration. By changing the # of samples to only 10% or 100% of the
input # of voxels, the computation times were the same.

Therefore, I suspect this may be because the SetNumberOfSpatialSamples()
function is by-passed somewhere down the path of implementation? 

Thanks for looking into this!


Luis Ibanez wrote:
> 
> Hi Pinpress,
> 
> You will have to increase by a lot the number of samples
> in order to notice an effect in the computation time.
> 
> If your real goal is to speed up the registration process,
> the most important thing to do is to make sure that
> you are compiling for "Release" mode, and to check
> if all the cores of your processor are being used at
> run time.
> 
> 
>      Regards,
> 
> 
>             Luis
> 
> 
> 
> --------------------------------
> On Fri, May 7, 2010 at 10:43 AM, pinpress <sb_ji at yahoo.com> wrote:
>>
>> Dear all,
>>
>> I am performing 3D image registration with data set size of
>> 256-by-256-by-124. Using normalized MI, or correlation coefficient, it's
>> really slow. Therefore, I have purposefully set
>> SetNumberOfSpatialSamples( )
>> to a small number, e.g., 10% of the total number of voxels. To my dismay,
>> it
>> does not seem to have any effect on the computation time.
>>
>> Can I ask what's the reason? I have already set the optimization flags to
>> be
>> "ON" when compiling ITK using cmake. Therefore, this function does
>> influence
>> computation time when I use Mattes MI or Mean Squares Difference as the
>> similarity measure.
>>
>> Please help. Thanks!
>> --
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>>
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> _____________________________________
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> 
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> 
> Kitware offers ITK Training Courses, for more information visit:
> http://www.kitware.com/products/protraining.html
> 
> Please keep messages on-topic and check the ITK FAQ at:
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