[deal.II] Where can I find member function of cell?

[yuesu jin]

Hi all,
  When we iterate the cell within triangulation/dof_handler, we often use
functions such as cell->face(), cell->vertices()  etc. Where can I find all
the member function in our documentation webpage? Thanks a lot!

-- 
Yuesu Jin,
Ph.D student,
University of Houston,
College of Natural Sciences and Mathematics,
Department of Earth and Atmospheric Sciences,
Houston, Texas 77204-5008
346-404-2062

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Re: [deal.II] Parallel distributed hp solution transfer

[Doug]

Thank you very much for the quick fix! Looking forward to pull this once it 
goes through all the checks.

Doug

On Sunday, August 25, 2019 at 9:44:29 AM UTC-4, Marc Fehling wrote:
>
>
> I came up with a fix for this issue in the following PR #8637 
>  that uses the CellStatus 
> flags to determine active_fe_indices while coarsening.
>
>

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Re: [deal.II] How to use FE_FaceQ with update_gradients.

[Wolfgang Bangerth]

On 8/26/19 1:09 PM, Lars Corbijn wrote:
> 
> Thank you for the detailed information. That sounds like a good solution 
> to the problem given the current situation.
> 
> Now that I have a working checkout (but waiting for a recompile), I will 
> see if I can find some spare time to program the solution.

Great! Feel free to open an issue on the deal.II github account that 
describes the problem, and then we can have discussions there if you 
have questions on how to address the problem. We can also reference that 
issue from all pull requests that address (parts of) it.

Best
  W.


-- 

Wolfgang Bangerth  email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

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Re: [deal.II] How to use FE_FaceQ with update_gradients.

[Lars Corbijn]

Wolfgang,

Thank you for the detailed information. That sounds like a good solution to
the problem given the current situation.

Now that I have a working checkout (but waiting for a recompile), I will
see if I can find some spare time to program the solution.

Lars

On Tue, 20 Aug 2019 at 00:54, Wolfgang Bangerth 
wrote:

>
> Lars,
>
> > I am trying to implement and HDG like method from [1], but without the
> > elimination process described in step 51. Thereby creating a block
> matrix.
> >
> > To implement this I use as finite element a system of FE_DGQ + FE_FaceQ.
> > On the face I need to compute integrals between the functions from the
> > trace space (i.e., from FE_FaceQ) and the normal times gradient of the
> > functions inside the element (i.e., from FE_DGQ). Therefore, I pass
> > update_gradients to FE_FaceValues, but this runs into the exception that
> > the gradients are not implemented for FE_FaceQ. Note that the lack of
> > gradients of FE_FaceQ is no problem, as its gradients are not need and
> > (I expect) not well defined, but I do need the gradients of FE_DGQ.
>
> I see the problem. I *think* that the right approach would probably be
> to remove the assertion in the fill_fe_values function of FE_FaceQ that
> you see, and instead fill the fields that should be filled with the
> gradients with some kind of numbers::signaling_nan() -- in other words,
> make sure that it's allowed to call the function with update_gradient,
> but also ensure that you're poisoning the returned values with values
> that will trigger a floating point exception once anyone tries to use
> them. (It is conceivable that these memory locations are already pre-set
> to have these signaling nans in them.)
>
> Do you want to give this a try and see whether you can come up with a
> patch?
>
> Best
>   W.
>
> --
> 
> Wolfgang Bangerth  email: bange...@colostate.edu
> www: http://www.math.colostate.edu/~bangerth/
>
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>

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Re: [deal.II] Mixed-precision algorithms in deal.II

[David Wells]

Hi Maxi,

The AffineConstraints class does not support using mixed precision and I am
not aware of any alternatives that can solve this problem directly.

There may be a better solution, but one way to solve this problem would be
to set up two different AffineConstraints objects (one for each floating
point type) and then call distribute_local_to_global with a (copied from
the single precision) double precision cell matrix and double precision
cell RHS and (for single precision) do the opposite. This will update both
the global matrix and global RHS correctly.

AffineConstraints objects will do Gaussian elimination with values taken
from the single precision cell matrix to determine the correct values for
the global RHS, so you will lose some accuracy in the RHS due to
truncation. It might be better to either set up both the matrix and RHS in
double precision and then copy the matrix over to single precision to avoid
this problem, or compute the cell matrix in double precision and copy it to
a single precision matrix (instead of the opposite approach given in the
previous paragraph).

Does this make sense?

Thanks,
David


On Mon, Aug 26, 2019 at 8:09 AM 'Maxi Miller' via deal.II User Group <
dealii@googlegroups.com> wrote:

> I tried to implement a simple mixed-precision algorithm in deal.II, which
> creates my matrix using float values, and my vectors using double values.
> Unfortunately, the function distribute_local_to_global(cell_matrix,
> cell_rhs, local_dof_indices, system_matrix, system_rhs) does not support
> mixed types. Is there an alternative function, or do I have to create two
> AffineConstraints-objects, initialize both with different values (double
> and float) and use them separately?
>
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> 
> .
>

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[deal.II] Mixed-precision algorithms in deal.II

['Maxi Miller' via deal.II User Group]

I tried to implement a simple mixed-precision algorithm in deal.II, which 
creates my matrix using float values, and my vectors using double values. 
Unfortunately, the function distribute_local_to_global(cell_matrix, 
cell_rhs, local_dof_indices, system_matrix, system_rhs) does not support 
mixed types. Is there an alternative function, or do I have to create two 
AffineConstraints-objects, initialize both with different values (double 
and float) and use them separately?

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