[petsc-dev] I think equispaced nodes are in the wrong place

[Toby Isaac]

The problem is that the node families come in two flavors: with endpoints
and without endpoints.  When you left the node family as `DEFAULT`, it knew
to choose "with endpoints" for continuous nodes, but by overriding the node
family it didn't.  I made an MR and fixed that logic.  You can fix it
before the MR gets merged from the command line with
"-potential_petscdualspace_lagrange_node_endpoints 1"

On Mon, Jul 7, 2025 at 3:04 PM Matthew Knepley <knepley at gmail.com> wrote:

> Try running this:
>
> make -f ./gmakefile test search="snes_tutorials-ex13_2d_p1_conv"
> EXTRA_OPTIONS="-potential_petscspace_degree 3
> -potential_petscdualspace_lagrange_node_type equispaced -petscds_view
> ::ascii_info_detail"
>
> You see that
>
> # >           Dual basis vector 0
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-0.333333, -0.333333) +1
> # >           Dual basis vector 1
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-0.25, -1) +1
> # >           Dual basis vector 2
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (+0.25, -1) +1
> # >           Dual basis vector 3
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (+0.25, -0.25) +1
> # >           Dual basis vector 4
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-0.25, +0.25) +1
> # >           Dual basis vector 5
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-1, +0.25) +1
> # >           Dual basis vector 6
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-1, -0.25) +1
> # >           Dual basis vector 7
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-1, -1) +1
> # >           Dual basis vector 8
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (+1, -1) +1
> # >           Dual basis vector 9
> # >               Quadrature on a unknown of order -1 on 1 points (dim 2)
> # >               p0 (-1, +1) +1
>
> but I think those should be +- 1/3, not 1/4. What is going on?
>
>   Thanks,
>
>      Matt
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
> https://urldefense.us/v3/__https://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!cmxlEUvaAY8SqXfiOuSkCpfTppdZ87z5AnqoBNY8TFup0nd5r-RL44RvjByulFlB3Fm9amh6iNF8hZ6MBUMZPiTy$ 
> <https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!cmxlEUvaAY8SqXfiOuSkCpfTppdZ87z5AnqoBNY8TFup0nd5r-RL44RvjByulFlB3Fm9amh6iNF8hZ6MBYv_M9MQ$ >
>
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