On 01/30/2018 07:53 AM, Dulcimer0909 wrote:
for(unsigned int i = 0; i < dofs_per_cell; i++)
{
for (unsigned int j = 0; j < dofs_per_cell; j++)
{
matrix_v.add (local_dof_indices[i],
local_dof_indices[j],
cell_matrix(i,j));
}
system_rhs(local_dof_indices[i]) += cell_rhs(i);
This is the place I pointed out in the other mail: you add to matrix_v
and system_rhs on each cell, but you never set them to zero.
> for(unsigned int i = 0; i < dofs_per_cell; ++i)
> {
> for(unsigned int j = 0; j < dofs_per_cell; ++j)
> {
> [...]
> cell_rhs_1(i) +=
> /*(MV^(n-1) - k(theta*A*U^(n) +
> (1-theta)*A*U^(n-1))*/
> (
> fe_values.shape_value(i, q_index) *
> fe_values.shape_value(j, q_index)
> *
> old_v
This cannot be correct. The assembly of cell_rhs_1(i) cannot include the
shape function shape_value(j,q_index). Assembly of the rhs must be in a
loop only over i, not in the loop over j.
As for debugging these problems, you should also try to run these sorts
of things on only one cell, for example. If you only change the system
assembly for the second equation, then output the rhs and matrix for the
v-system just before solving for both of the old code and for your
modification. They need to be the same. If they're not, you know where
your problem lies.
Best
W.
--
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Wolfgang Bangerth email: [email protected]
www: http://www.math.colostate.edu/~bangerth/
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