[Insight-users] Workings of RegularStepGradientDescent Optimizer (with BSplineDeformableTransform)

[Luis Ibanez]

Hi Christian,


This optimizer does the following


    A)  Compute Gradient of the Cost function at initial point
    B)  Use current step length to multiply the unit vector
          of the gradient computed in (A)
    C)  Jump from current point to new point using the vector
          computed in (B)
    D)  compute direction of jump in (B) with the one of the
          previous iteration (by scalar product).
    E)  If directions are opposite, then reduce Step Length
          by the "Relaxation factor" (which by default is 0.5).
    F)  If current Step length is larger than Minimum Step
         length then goto (A).
    G) Otherwise, stop.



    Regards,


            Luis


--------------------------------------------
On Fri, Jul 24, 2009 at 1:26 PM, c23562 <c.popko at gmx.de> wrote:

>
> Hi all,
>
> Where i can learn something about the workings of
> RegularStepGradientDescent
> Optimizer? I would like to know what exacly is a step? What is changing
> when
> doing a step?
> I have an imagine about regularStepGradientDescent optimizer and
> translation
> transform but what about BSplineDeformable transform? I have no idea what
> happens if the optimizer is working.
> I have read the ITKSoftwareGuide and read all lectures. There is described
> what happens if the optimizer is used with curves like parabolas but what
> about the contour lines in BSplineDeformableTransform?
>
> Thanks in advance and best regards,
> Christian
> --
> View this message in context:
> http://www.nabble.com/Workings-of-RegularStepGradientDescent-Optimizer-%28with-BSplineDeformableTransform%29-tp24648554p24648554.html
> Sent from the ITK - Users mailing list archive at Nabble.com.
>
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