[petsc-users] basis functions of high order approximation (FE)

[Yann Jobic]

It's clear now !

Many thanks for the explanations.

Yann

On 08/01/2019 17:30, Jed Brown wrote:
> Yes, tensor product of Lagrange polynomials, often written as Q_k.
> Degrees of freedom associated with Dirichlet boundary conditions have
> been removed in the systems you're looking at.
>
> Yann Jobic via petsc-users <petsc-users at mcs.anl.gov> writes:
>
>> Dear Petsc Users,
>>
>> I've been playing with the option "space_degree", in 2D, for a space
>> discretisation of 4 cells (2x2), for a poisson problem, and i wonder
>> what are the underlying concepts.
>>
>> With a space degree 2, i get a    9x9   algebraic system, and i've got a
>> solution convergence order of 3.
>>
>> With a space degree 3, i get a 25x25 algebraic system, and i've got a
>> solution convergence order of 4.
>>
>> So my question is : what are the basis functions associated with each
>> space degree ?
>>
>> Are they lagrange polynomials or something else ?
>>
>> Thanks!
>>
>> Yann