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

[Yann Jobic]

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