[Libmesh-users] Problem accessing a dof index in a system

[Miguel A. S. de T. <sal...@gm...>]

Hi everybody

I have an EquationSystem with a FEMSystem that has just a LAGRANGE_VEC
variable, which I use to solve my problem, and another ExplicitSystem with
a zeroth order MONOMIAL variable to define a parameter in each element.

Before calling  equation_systems.init(), I assign initial values for each
degree of freedom in my ExplicitSystem. I do it in a similar fashion to
example system_of_equations_ex6 (there an ExplicitSystem is used to compute
the stresses) I close the system's current solution and update the system.

Then I solve my FEMSystem and calculate its sensitivities. In the process,
I call the variable in my ExplicitSystem because I am using it as a
parameter for the sensitivities. I want to do the perturbation to verify my
sensitivities, so I perturbate the variable in the ExplicitSystem. I try to
obtain the value here again with a similar fashion to example
system_of_equation_ex6, but it fails. Specifically it fails when I call

aux_system.current_local_solution->get(densities_index, density);

where aux_system is my ExplicitSystem. I found out that densities_index
doesn't have the correct index because it contains an invalid id. In
DofMap::_dof_indices, I can only get to

di.resize(di.size() + nc, DofObject::invalid_id);

I've been debugging this and I found out that the problem is in the
DofObject array _idx_buf. When I assigned initial values for the variable
in the ExplicitSystem, This array was something like

2 , 4 , 256 , 4294967294, 257 , 0

but when I try to access the dof indices when calculating the densities the
array is

2 , 4 , 256 , 4294967294, 256 , 4294967294

This way when the function

elem->n_comp(sys_num,v))

is called, it returns 0 instead of 1 (because it returns the value in index
4, which is 256, before it was 257)

I think I must be missing calling a function to reinitialize the system or
something similar. Please let me know if it's necessary that I upload the
code on github or if you need more details. I hope this problem is not too
complicated. Thanks in advance.

Miguel

-- 
*Miguel Angel Salazar de Troya*
Graduate Research Assistant
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
(217) 550-2360
sal...@il...