Yeah, Roy is right, better to use quadrature.
The approach I suggested initially would require you to project the exact
solution into the FE space first, but you probably want to avoid that since
it introduces a projection error into your calculation.
David
On Tue, Jan 19, 2016 at 6:20 PM, Roy
This may not be what you want to do, IMHO.
In the extreme case: If you compute the Uexact vector and then do the
vec*mat*vec, then you'll get a result of 0 for problems where your
method gives you an interpolant of the exact solution, even if that
interpolant doesn't equal the exact solution.
If
Thanks, that is helpful.
--Junchao Zhang
On Tue, Jan 19, 2016 at 4:10 PM, David Knezevic
wrote:
> Assemble the Uexact vector, then compute the difference e = U - Uexact.
>
> You can also refer to error_estimation/exact_solution.h, but I believe
> that's used for computing L2 or H1 error, not an
Assemble the Uexact vector, then compute the difference e = U - Uexact.
You can also refer to error_estimation/exact_solution.h, but I believe
that's used for computing L2 or H1 error, not an arbitrary energy norm.
David
On Tue, Jan 19, 2016 at 5:04 PM, Junchao Zhang
wrote:
> How to get e =
How to get e = U - Uex? Is there a libmesh interface for that?
--Junchao Zhang
On Tue, Jan 19, 2016 at 3:57 PM, David Knezevic
wrote:
> Assuming you've already assembled K, so you can just do a matvec
> (SparseMatrix::vector_mult) followed by a dot product (NumericVector::dot).
>
> David
>
>
>
Assuming you've already assembled K, so you can just do a matvec
(SparseMatrix::vector_mult) followed by a dot product (NumericVector::dot).
David
On Tue, Jan 19, 2016 at 4:53 PM, Junchao Zhang
wrote:
> Hello,
> I want to compute e^TKe as a measure of the error of a solution. Here e =
> U -
Hello,
I want to compute e^TKe as a measure of the error of a solution. Here e =
U - Uex, supposing I know the analytic answer to the PDE.
How can I do it in libmesh? Is there an example?
Thank you.
--Junchao Zhang
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