ffc team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

I don't see how to do this. As I understand, you have two matrices and 
you want to compute their product. So you want to compute a sum of 
products of integrals. I don't know how to write this as a single 
integral (other than as a "double integral" over the square of the domain).

What is the quantity you want to compute in the end? Can you write it as 
a single integral?

/Anders


Alessio Quaglino wrote:
> I have a question about matrix multiplication in FFC. Say I want to
> measure a certain quantity S in respect to a test function psi belonging
> to the same finite space:
>
> S = dot(u, psi) (1)
>
> and then I want to use this measure to assemble the bilinear form where
> phi is taken from the same finite space of u:
>
> A = dot(S, grad(phi)) (2)
>
> this is equivalent to assemble the bilinear form (1) obtaining the "m x n"
> matrix S and then the bilinear form (2) obtaining the "n x m" matrix A.
> Then what I need is to perform the multiplication A*S getting a "n x n"
> matrix. Can I write A in such a way that this is done directly in the
> form? Do I have to define a trilinear form?
>
> Thanks,
> Alessio Quaglino
>
>
>
>
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