Status of support for complex equations?

[Maxi Miller]

Hei,
I was wondering if dealII already natively supports equations containing imaginary values, such as
 
or if I still have to split them up, such as in example 29?
Thank you!

[Matthias Maier]

Hi,

On Wed, Jul 19, 2017, at 09:59 CDT, "'Maxi Miller' via deal.II User Group" <dea...@googlegroups.com> wrote:

> Hei,
> I was wondering if dealII already natively supports equations containing
> imaginary values, such as
>

> <https://lh3.googleusercontent.com/-XNa7LZRlhVg/WW9zfQag28I/AAAAAAAACQM/L-zw-v0Kg9k8kKV4YybVSpr8g3DwbzjMwCLcBGAs/s1600/simple_equation.png>

> or if I still have to split them up, such as in example 29?

Most of the data structures (such as system matrix and vectors and
tensor classes) are templated in number type so you can simply use them
to store complex numbers.

We also support PETSc with complex number support, so you also get
solvers that might work directly with complex-valued objects.

However, for practical purposes (and after having worked with deal.II in
context of time-harmonic Maxwell's equations) I recommend splitting into
a real-valued block structure right from the beginning. It is simply
much more flexible when it comes to choice of underlying linear algebra
package and solvers.

I hope that helped a bit.

Best,
Matthias

[Denis Davydov]

Have a look at this issue which aggregates efforts in this direction: https://github.com/dealii/dealii/issues/2033

Essentially, the main missing piece is ConstraintMatrix https://github.com/dealii/dealii/issues/1760 

which Matthias wanted to do over the weekend in July 2016 :-) I think there is a prototype branch, 

so if you need to work with complex-valued algebra, you might want to look at this issue.

Cheers,

Denis.

[Matthias Maier]

On Tue, Jul 25, 2017, at 14:24 CDT, Denis Davydov <davy...@gmail.com> wrote:

> which Matthias wanted to do over the weekend in July 2016 :-)

<_<

Long weekend! *cough*

Best,
Matthias