Dear all,
I am solving a 3x3 block system arising form DG time discretisation of the
semilinear parabolic equations in the form u_t - \Delta u = f(u) for the
block solution vector U which consists from three nodal values blocks U0,
U1 and U2. During the solution process I need just the solution values of
the second block U1 at the previous time steps (t_{n-1}, t_{n-2} and
t_{n-3})
i.e. old_solution.block(1), old_old_solution.block(1) and
old_old_old_solution.block(1) for this task I used
std::vector<Vector<double> old_solution_values (n_q_points,
Vector<double>(3));
std::vector<Vector<double> old_solution_values0 (n_q_points,
Vector<double>(3));
std::vector<Vector<double> old_solution_values1 (n_q_points,
Vector<double>(3));
fe_values.get_function_values (old_solution, old_solution_values);
fe_values.get_function_values (old_old_solution, old_solution_values0);
fe_values.get_function_values (old_old_old_solution, old_solution_values1);
In the solution process in the right hand side assembly I need just the
nodal values of second block U1 at the previous time steps (t_{n-1},
t_{n-2} and t_{n-3}) i.e. old_solution.block(1)
For this reason, I used
const double old_s = old_solution_values[q_point](1);
const double old_s = old_solution_values0[q_point](1);
const double old_s = old_solution_values1[q_point](1);
but I did not get required results and even when I changed
old_solution_values[q_point](1) to old_solution_values[q_point](0) nothing
has changed (just to check if there is any difference) and even when I
tried the wrong thing old_solution.block(1) nothing has changed and I got
the same results as with previous other cases.
I am confused about this case; did I do some thing wrong in defining the
nodal values of the second block of the solution vector at the previous
time steps? Any feedbacks and hints are appreciated.
Best regards
Mohammad Sabawi
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