Am 22.05.2013 22:50, schrieb Luc Maisonobe:
> I am not sure I understood your use case properly. I'll look at it further in the next
few days.
>
> A first very quick answer is that the interface as it is defined does not seem to correspond
to your needs.
> In the current interface, the meaning of the two "value" method is the same. So the various
elements in
> The point array should be the same. In your case, I think you already use the array to
represent derivatives
> of the first element, so I think you expanded the content of what should be a single
DerivativeStructure instance as a double array.
>
> Are you sure you should not use a univariate function ? The DerivativeStructure argument
you would get
> would contain all the partial derivatives already.
>
> Once again, I'm not sure I understood your example properly as I did not find the time
to think about it for now.
>
> Best regards,
> Luc
Hi Luc,
I am trying to motivate the problem:
Consider the simple pendulum equation
x² + y²  L² = 0
I could use DerivativeStructure to solve for that equation by using e.g.
NewtonRaphson.
But in a model, x and y are actually depending on the free variable t,
so I may require the total derivative of the above equation, e.g.:
2*x*dx + 2*y*dy = 0
Again, I want to be able to solve for that equation by using an
iterative method. The thing is: This total derivative has now more
parameters than the original equation (namely dx and dy).
If I model it that way, I can pass the x and y parameters to the base
function, evaluate the partial derivatives (2x and 2y) and multiply them
with the total derivatives dx and dy. The problem here is that the
baseequations partial derivatives are not constant (the second order
partial derivatives are, though). So I somehow need to reflect that for
the numerical solver. That's why I thought, I should make the derivative
also a MultivariateDifferentialFunction.

Christoph Höger
Technische Universität Berlin
Fakultät IV  Elektrotechnik und Informatik
Übersetzerbau und Programmiersprachen
Sekr. TEL122, ErnstReuterPlatz 7, 10587 Berlin
Tel.: +49 (30) 31424890
EMail: christoph.hoeger@tuberlin.de

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