[Insight-developers] single valued cost function

[Ziv Yaniv]

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.

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
Fax: +1-202-784-3479
email: zivy at isis.georgetown.edu
web: http://isiswiki.georgetown.edu/zivy/