Gradient Postprocessor not working

[Abbas]

So I copied what's in the link verbatim to step 8 but it says that I am "trying to use functionality in deal.II that is currently not implemented" 
I attached the code below. 
I'll use the default approach for outputting gradients of a vector; is there a dealii step that does this?  

[Wolfgang Bangerth]

On 11/8/22 09:11, Abbas wrote:
> *** Caution: EXTERNAL Sender ***

>
> So I copied what's in the link

> <https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2FclassDataPostprocessorTensor.html&data=05%7C01%7CWolfgang.Bangerth%40colostate.edu%7Cc98d01e4aa464ed9fb3808dac1a3d7e0%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C638035207831485386%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000%7C%7C%7C&sdata=dGblC2ovakBl3ham3jsHZX2VHuCqOefmWOp%2Fg%2BLja2I%3D&reserved=0> verbatim

> to step 8 but it says that I am "trying to use functionality in deal.II
> that is currently not implemented"

The problem doesn't actually have anything to do with the postprocessor,
but with the fact that you're outputting your data in VTK format (using
data_out.write_vtk(...)). That function does not support tensor output,
either because we didn't implement it or because the VTK file format
doesn't support tensors -- I don't recall. In any case, switch to
write_vtu() instead and everything should work.

Best
W.


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

[Abbas]

That was a quick fix and it works.  
Just changed "data_out.write_vtk (output);" to "data_out.write_vtu (output);" 
Thanks 

Doxygen fixes are done with a PR too? Can I do it?  It will take me forever tho. 

[Wolfgang Bangerth]

On 11/10/22 08:27, Abbas wrote:
>
> Doxygen fixes are done with a PR too? Can I do it?  It will take me
> forever tho.

Yes, and we always appreciate these kinds of PRs as well!

In this case, I beat you to it yesterday already, though:
https://github.com/dealii/dealii/pull/14407/files