Defining multiple local meshes using buildDmesh

General Discussion
1

Hello all,

I am using the macro_ddm.idp to use buildDmesh and createMat with macro def(i) [i, i#B, i#C] // to solve the 3D elasticity equation in parallel using PETSc. I also need to solve a 1D and 2D varf in the same parallel script - how can I solve the varf of different dimension using the same local mesh, or how can I define another local mesh with different dimension (ex. def(i) i// ) using buildDmesh?

Thank you.

2

Are your 1D and 2D meshes somehow related to the 3D mesh?

3

Yes - they use the same 3D global mesh.

4

Could you please share a minimalist sequential script with your various global meshes so that it’s better to see how they interact one with another?

5

I’ve attached a simplified sequential version (ie. no mesh decomposition). The solver doesn’t work in this sequential case, but this is just so you can see what I intend to do/solve.

Example.edp (6.0 KB)

6

I just see a single 3D mesh Omega in this script, is this alright?

7

Yes - that is the single domain over which the integrals in both varfs are applied.

8

But both varf are defined on Omega, your single 3D mesh. You said initially that you have “1D and 2D varf”, but I don’t see any varf using either a mesh or meshL.

9

If the “only” issue is mixing vectorial and scalar finite element spaces, you can just do the following.

load "PETSc"
macro dimension()3//
include "macro_ddm.idp"

mesh3 Omega = cube(10, 10, 10);

buildDmesh(Omega);
Mat A, B;
{
    macro def(i)[i, i#B, i#C]//
    macro init(i)[i, i, i]//
    createMat(Omega, A, [P2, P2, P2]);
}
{
    macro def(i)i// not mandatory
    macro init(i)i// not mandatory
    createMat(Omega, B, P1);
}
10

This is what I was trying to explain - thank you! My apologies for doing such a poor job at explaining, but this is exactly what I was trying to figure out.

Thank you again!

11

OK, good then! No problem at all :smile:

12

Hi Pierre!

How about solving in the same parallel script a problem in one mesh and another in a part of this mesh. For example, if you consider a 2D mesh and then solve a problem into a 1D mesh extract from this 2D mesh.

13

Not a problem at all, in fact, that’s exactly what’s done in, e.g., FreeFem-sources/examples/hpddm/helmholtz-coupled-2d-PETSc-complex.edp at develop · FreeFem/FreeFem-sources · GitHub.