Tensor product polynomials

[Giselle Sosa Jones]

Hello,

I need to create a local space of polynomials in 3D of the form Q_{k-1,k,k} \times Q_{k,k-1,k} \times Q_{k,k,k-1}. This space is very similar to the DG Raviart-Thomas space, with the difference that the polynomial order of each component is one order lower in the corresponding direction. I was looking at the file polynomials_raviart_thomas.cc to get an idea of how to create them but I am a bit lost. Can someone offer a suggestion?

Thank you.

Kind regards,

Giselle

[Wolfgang Bangerth]

Giselle -- can you be specific about which part you have trouble with?
I've tried to improve the documentation of the key function of that
class a bit:
https://github.com/dealii/dealii/pull/12726

Best
Wolfgang

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

[Giselle Sosa Jones]

Thank you, Dr. Bangerth, I think these extra comments clarify it for me.

Best,

Giselle

[Giselle Sosa Jones]

Hello,

I sent this message a while ago and things became clearer for me, but I am still not able to create the spaces that I want. My goal is to create local spaces that look like this: Q_{k-1,k,k} \times Q_{k,k-1,k} \times Q_{k,k,k-1}, for k \geq 1.This is what I am currently doing:

- Created my own class of polynomials similar to the deal.II class PolynomialsRaviartThomas, but with the polynomial degrees as described above.

- Created my own class (FE_RTProj) for a finite element space similar to the one called FE_DGRaviartThomas. This is a derived class from FE_DGVector and the polynomial type is the one created in the item above.

My code does not even compile since I get error messages like: error: undefined reference to 'FE_RTProj::FE_RTProj<2, 2>::get_name[abi:cxx11]() const. The function get_name is defined in the FE_RTProj h and cc files (I basically copied from  FE_DGRaviartThomas). I am not sure if this is a C++ issue and/or if there is an easier way of doing this.

Any help is highly appreciated!

Best,

Giselle Sosa Jones

[Wells, David]

Hi Gisselle,

This error message occurs when you use a very old (probably GCC 4.8 or 4.9) C++ compiler with a version of deal.II built with a newer C++ compiler (or vice versa). A sure fix is to make sure you use the same compilers both for your code and the library. In practice, though, the ABI change occurred in GCC 5 so combining any two newer versions is typically okay.

Best,

David

---

From: dea...@googlegroups.com <dea...@googlegroups.com> on behalf of Giselle Sosa Jones <gisel...@gmail.com>
Sent: Tuesday, May 31, 2022 11:55 AM
To: deal.II User Group <dea...@googlegroups.com>
Subject: Re: [deal.II] Tensor product polynomials

 

You don't often get email from gisel...@gmail.com. Learn why this is important

--
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 dealii+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/f3388a43-fe77-4c01-a346-1a7fb89d243dn%40googlegroups.com.

[Giselle Sosa Jones]

Hi David,

I've tried updating my C++ compiler and recompiling deal.II, but I have the same error. It is as if the hh file is not recognized in the cc file. I know this is a long shot, but do you happen to have any other suggestions? Maybe there is an easier way to create this space that I need?

Thank you!

Best,

Giselle

To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/MN2PR03MB4879589A5424DA0E1259B82DEDDC9%40MN2PR03MB4879.namprd03.prod.outlook.com.

[Wells, David]

Hi Giselle,

What do you mean by "the hh file is not recognized in the cc file" - is there a specific error message this refers to?

In general, if you need to implement a new finite element, you will need to write some code. Can you compile any program that depends on deal.II right now?

Best,

David

---

From: dea...@googlegroups.com <dea...@googlegroups.com> on behalf of Giselle Sosa Jones <gisel...@gmail.com>

Sent: Wednesday, June 22, 2022 10:45 AM
To: dea...@googlegroups.com <dea...@googlegroups.com>

To view this discussion on the web visit https://groups.google.com/d/msgid/dealii/CA%2B_N%3DLNfh4-669dtY81dY%3Dkfbwro%3DoCfO7BJO_tVE4cd_SqJuw%40mail.gmail.com.