On Mon, Dec 04, 2006 at 07:51:51PM +0100, Garth N. Wells wrote:
Anders Logg wrote:
On Mon, Dec 04, 2006 at 07:32:34PM +0100, Garth N. Wells wrote:
Anders Logg wrote:
On Mon, Dec 04, 2006 at 07:20:22PM +0100, Garth N. Wells wrote:
Anders Logg wrote:
On Mon, Dec 04, 2006 at 06:03:41PM +0100, Garth N. Wells wrote:
Anders Logg wrote:
I think of a node as a member of the dual basis for P in the
definition of a finite element in Brenner-Scott. A node in FFC is
always associated with an entity, like the second node of entity 0 of
an entity of dimension 1 (the second node on the first edge).
So I would very much like to keep the name "node".
OK, but this does clash with accepted terminology. In both Brenner &
Scott and Ciarlet, nodes are defined as points.
Yes, when I look again, they do use "node" for a point, but also refer
to "nodal variables" as the name of the linear functional you evaluate
to get the "nodal value".
Sure, this is normal FE terminology - nodal variables for the degrees
of freedom at a node. Also, "nodal value" in general case should be
"nodal values" :).
ok, but how do you say this when the nodal variable is an integral
over an edge?
Can you still say "at a node"? Or is "node" not used then?
I wouldn't use node, I would use "degree of freedom". Are you thinking
of a Nedelec element?
Garth
I was thinking BDM.
So your suggestion is to never use "node" and always use "dof"?
Not quite. I would restrict the meaning of "node" to a position point,
and use degree of freedom for a value that can change, typically
representing the amplitude of some function.
I looked quickly in a few books and they refer to "degrees of freedom"
for BDM and Nedelec elements.
Garth
I asked Ridg to settle this. Here's a quote:
There is a good reason to differentiate between the point at which
a nodal variable acts and the nodal variable (the linear functional).
Using DOF for this concept is probably the best idea, since the
terminology "nodal variable" still refers to a "node" and does not
sound quite right for an edge integral.
Ridg
So I give up, let's call it "dof"/"DOF"! :-)
