Subject: [FEniCS-users] quadrature element

From: Patrick Riesen <[email-masked]>
Date: Fri, 13 Nov 2009 13:52:14 +0100

hello,

before dolfin0.9.2/ffc0.7 i used a quadrature element to compute and 
manipulate a variable viscosity for a nonlinear problem.

In >= dolfin0.9.3+/ffc0.7 i got the complaint that basis-functions are 
not anymore defined for a quadrature element, so i'm now using a DG 
element with order-1 of the quad element i used.

it works, but the convergence rates of the newton solve for my actual 
problem are not quadratic anymore. Especially for a small number of 
gridpoints it's very bad, but gets better (almost quadratic) if i use a 
very fine mesh. anyway, i didn't had this before.

does somebody have a guess or a hint on this problem?

many thanks,

patrick