[Insight-developers] single valued cost function

[Karthik Krishnan]

On Fri, Jul 16, 2010 at 12:02 AM, Ziv Yaniv
<zivy at isis.imac.georgetown.edu>wrote:

> What was the reasoning behind having the GetValueAndDerivative and the pure
> virtual GetDerivative method in the SingleValuedCostFunction class? This
> does not accommodate non differentiable functions in a natural way.
>
> I see two options:
>
> Slight modification of the current cost function hierarchy,
> 1. Remove both methods from the SingleValuedCostFunction class.
> 2. Add a class SingleValuedCostFunctionWithDerivative adding the two
> methods and inheriting from SingleValuedCostFunction
> 3. Modify the inheritance of the direct subclasses (7 according to doxygen)
> from the old class to the new one.
>

Don't you also need to to include a similar additional hierarchy in the
optimizers, since the hierarchy of cost functions should be matched by the
space of optimizers.

There are only two kinds of cost functions : (a) single valued multivariate
(b) Multivalued multivariate cost functions. Likewise there are two kinds of
optimizers as well.

thx
--
karthik


>
> No change to code base,
> 1. Implementation of GetDerivative in a subclass that cannot compute one
> just throws an excpetion. Ugly but guaranteed to get the developers
> attention.
>
> Am I missing something? If not, I would be happy if itk-v4 adopts the first
> option.
>
>                   Ziv
>
>
> --
> Ziv Yaniv, PhD., Research Assistant Professor
> Imaging Science and Information Systems (ISIS) Center
> Department of Radiology
> Georgetown University Medical Center
> 2115 Wisconsin Avenue, Suite 603
> Washington, DC, 20007,
>
> Phone: +1-202-687-7286
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> email: zivy at isis.georgetown.edu
> web: http://isiswiki.georgetown.edu/zivy/
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