Hello, guys.
I am doing a problem which is similar to the Sine-Gordon equation
(Step-25). The program gets running correctly without AMR, which is the way
of Step-25. I am using the total energy of the system as the primary
indicator. However, when I include AMR, even only on the initial condition,
things go wrong (total energy blows up).
The initialization part looks like this (comment the for-loop if without
AMR):
make_mesh();
setup_system();
init();
for (unsigned int init_refine = 0; init_refine < 5; ++init_refine)
{
refine_mesh();
init();
}
I don't know exactly where is wrong. Maybe someone once had a similar
problem, then please give me some ideas..
Now I am thinking that if I implement the hanging node constraints
correctly, since for a grid without AMR, there is no hanging nodes, while
they are introduced in with AMR.
Specifically, I am quite confused with the two functions: condense() and
distribute(). Here are a few questions:
1) Do they do harm if I accidentally apply them twice, or apply them when
they are not needed? for example,
constraints.condense(matrix, vector);
constraints.condense(matrix, vector);
or
constraints.distribute(vector);
constraints.distribute(vector);
2) It seems condense() is only used when we have assembled a linear system,
and prepare to solve it.
constraints.condense(system_matrix, system_vector);
Thank you!
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