Dear Eloi,
I think what you are looking for is something like this
md.add_filtered_fem_variable("u", V, region)
M = gf.asm_generic(IM, 2, "Test2_u*Test_u", region, md)
K = gf.asm_generic(IM, 2, "Grad_Test2_u.Grad_Test_u", region, md)
M = scipy.sparse.csc_matrix((M.csc_val(),*(M.csc_ind()[::-1])))
K = scipy.sparse.csc_matrix((K.csc_val(),*(K.csc_ind()[::-1])))
BR
Kostas
On Thu, Jun 30, 2022 at 4:57 PM Eloi Martinet <eloi.marti...@univ-smb.fr>
wrote:
> Hello,
> I'm using the python interface of GetFEM. My goal is to compute the
> laplace eigenvalues on a region of a spherical mesh, as follows (suppose
> the mesh, integration method IM and meshfem V is already declared):
>
> # Assemble the stiffness and mass matrices
> md = gf.Model("real")
> md.add_fem_variable("u", V)
> Kg = gf.asm_generic(IM, 2, "Grad_Test2_u.Grad_Test_u", region, md)
> Mg = gf.asm_generic(IM, 2, "Test2_u*Test_u", region, md)
>
> # Convert to scipy sparse
> K = getfem_to_scipy_sparse(Kg)
> M = getfem_to_scipy_sparse(Mg)
>
> # Compute the eigenvalues
> eVal, eVec = scipy.linalg.sparse.eigsh(K, k+max_multiplicity+1, M,
> sigma=0, which='LM', v0=v0)
>
> however, the size of the matrices K and M are the same as V.nbdof()
> whereas it should have less since the region isn't the whole mesh.
> Moreover, when I try to use the function "basic_dof_on_region", I get the
> following error :
>
> NameError: name 'basic_dof_on_region' is not defined
>
> I saw the things about the extension matrices but this is not clear to me
> how to construct it from the label of the region. So my question is what is
> the best way to compute eigenvalues on a region ?
>
> Thank you for your help and have a good day.
> Eloi MARTINET.
>
