Dear Daniel,
the problem is, as far as I can tell, the fact that once you assemble
into a matrix and once into a vector. The paper
K. Kormann: A Time-Space Adaptive Method for the Schrödinger Equation,
Commun. Comput. Phys. 2016, doi: 10.4208/cicp.101214.021015a
describes this effect in section 5.3. Can you check there if this is
what you see?
Best,
Martin
On 02.05.2018 20:17, Daniel Jodlbauer wrote:
But thats exactly my point, the error occurs in the dofs which
constrain a hanging node, not the hanging nodes (dofs 5 and 7) itself.
I agree that the constrained dofs 5 and 7 can have arbitrary values.
I will check whether the solution is going to be different in any
case. I was just afraid that wrong values on the diagonal could cause
problems in the MGSmoother afterwards.
On Wednesday, May 2, 2018 at 7:38:29 PM UTC+2, Wolfgang Bangerth wrote:
Daniel,
> To verify my MatrixFree implementation, I compared its
application to
> the classical matrix-vector multiplication (call it matrix *A*).
> This is done by computing the matrix *M* of the operator *MF* by
> applying it to all unit-vectors.
>
> However, when I compute the diagonal in the same way as
LaplaceOperator
> does it (copied it), I get values different from the assembled
diagonal
> once I have hanging nodes.
The rows and columns corresponding to hanging nodes are empty with
the
exception of the diagonal entry -- for which we use a value that
has the
correct order of magnitude, but that is otherwise unspecified. In
other
words, what diagonal value you have there is unimportant as long
as it
is nonzero because these degrees of freedom don't couple with all
of the
other degrees of freedom, and as long as you overwrite the values
of the
computed solution through ConstraintMatrix::distribute().
It is not surprising to me that you get different diagonal entries
when
you use two different methods. The question is whether you get a
different *solution* vector after distributing to hanging nodes.
Best
W.
--
------------------------------------------------------------------------
Wolfgang Bangerth email: [email protected] <javascript:>
www:
http://www.math.colostate.edu/~bangerth/
<http://www.math.colostate.edu/%7Ebangerth/>
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google
Groups "deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send
an email to [email protected]
<mailto:[email protected]>.
For more options, visit https://groups.google.com/d/optout.
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups "deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
