# Was "intall0d" intended for any purpose?

I was trying to find a way to just get the matrix for a differential equation ( no integration/ bilinear form ). That is just the matrix of an expression containing various derivatives on some fespace.

I found some things like “int0d” and most recently “intall0d” which
sounds like what I’m looking for but it is not used anywhere.

grep -n  "intall0d" `find src -type f -name "*"`  | grep enum
src/fflib/problem.hpp:285:  enum typeofkind  { int2d=0, int1d=1, intalledges=2,intallVFedges=3, int3d = 4, intallfaces= 5,intallVFfaces=6,int0d=7,intall0d=8 } ; //3d

I was going to add something like “intzed” for this purpose since I can’t find another way
to get there. Thanks. Just making some matricies from varf I think I mostly understand
what is going on and at least for P0 elements things look about right by inspection

Can you given a small exact of matrix construction, because you need to explain howto convert function in number to build the matrix.

I just wanted to get the matrix representing a discretized differential equation- not the
variaional integral . I was wondering if that had something to to with support for strong form.
Thanks.

So you want to make finite difference scheme!

Well, that is intermingled lol. I have a case I’m doing for learning but also a start
on a practical application. It is just diffusion but with a spatially varying diffusivity
that depends on the species concentations. In essence, it is like a two component
glue such as epoxy with one component circulating in an inert state activated
at a surface. When the activated hardener meets the flue, the diffusivity drops.

Right now I’m doing finite difference along the time axis . And yes I wanted to get
the depednence of the time derivatives on the contirbutors to the laplacian.
But, it should be independent of that. That is, you can get a matrix in
FEM right? Its just now you only support the weak form.

Thanks.

OK, for me the more simple to have the equation and start in 2d. with time,

you have 2 concentrations c1,c2 depending of space and time

and the minimal equation are something like :

d c1/dt - div( k1(c1,c2) grad(c1)) = ???
d c2/dt - div( k2(c1,c2) grad(c2)) = ???

tHis problem is hard a level of modélisation ,
I found a thesis on this subject in french : Modelization of the joint formation phase of a solvent-based adhesive in a porous medium - Archive ouverte HAL

Thanks. yes this is just diffusion. If there is interest and I get most of the
junk code removed, I can post the code. I realized I may be able to do this
even with the integration, I’m sure its just something dumb I was missing.