question about SampleMeshManager

[gokhalen]

I might be missing something, but I was looking at the following code to construct a sample mesh

libROM/examples/prom/nonlinear_elasticity_global_rom.cpp

Lines 885 to 900 in c3bfef5

	ParFiniteElementSpace* sp_XV_space;
	smm = new CAROM::SampleMeshManager(spfespace);
	vector<int> sample_dofs_empty;
	vector<int> num_sample_dofs_per_proc_empty;
	num_sample_dofs_per_proc_empty.assign(num_procs, 0);
	smm->RegisterSampledVariable("V", 0, sample_dofs,
	num_sample_dofs_per_proc);
	smm->RegisterSampledVariable("X", 0, sample_dofs,
	num_sample_dofs_per_proc);
	smm->RegisterSampledVariable("H", 0, sample_dofs,
	num_sample_dofs_per_proc);
	smm->ConstructSampleMesh();

It is surprising to be that there is no code/argument to set the error bound in constructing the sample mesh. I'm thinking that one should be able set the error bound in constructing the sample mesh. e.g. If I wanted less than 1% error the sample mesh would contain much more elements than if I wanted less than 25% error.

Maybe I'm missing something. Maybe I should be reading the original papers.

Thanks,

Nachiket

[JacobLotz]

Based on your question I think you are expecting that the sampling of DOFs is performed in SampleMeshManager. Am I right? The SampleMeshManager is used to construct a FiniteElementSpace containing the sampled variables determined with for instance the DEIM. It does not sample itself.

I think the answer on issue #187 will give clarity.

[gokhalen]

@JacobLotz Thanks, your answer makes it more clear. After looking at the code, DEIM/S_OPT/GNAT determines the sample_dofs and then the SampleMeshManager builds a FiniteElementSpace. As for my question about the error, I guess the error is implicitly determined by the number for basis vectors/reduced space dimension for V', 'X', 'H'. DEIM/S_OPT/GNAT will determine the best dofs to sample, given the basis vectors and basis size. There is no direct parameter to set the error of the ROM and then determine a sample mesh.