Dear all,
Its been a week since my latest post, I was just wondering if you could
help me.
Best,
Joel
On Tuesday, September 20, 2016 at 9:12:23 AM UTC+2, Joel Davidsson wrote:
>
> Dear Daniel,
>
> To clarify what I am searching for, I would like to get the vector-valued
> solution into a format that matches a scalar. Either as a
> std::vector<Tensor<1,dim>> or a std::vector<Point<dim>>, the format doesn't
> matter as long as it matches a scalar dofs. So I can manipulate the vector
> components and for example get the size.
>
> I made a test program that I have attached, that takes the gradient of a
> gaussian function. At line 354, I do the convergence from a vector valued
> solution to get the size of the vector (as I posted before). This was wrong
> and you guys said that I shouldn't assume any particular order of the dofs.
> Then I tried to this conversion the correct way, see line 365, but I do not
> know how to do this conversion the correct way.
>
> The code I have sent you, produces the correct result for fe1 and fe2,
> i.e. when I set fe_scalar (2), fe(FE_Q<dim>(2),dim) at line 100. But failed
> for fe3. I have attached the result I got for fe2 and fe3 as well as the
> plot script I have used to generate these plots.
>
> I would be really grateful if you could help me figure out how to solve
> this.
>
> Best,
> Joel
>
> On Monday, September 19, 2016 at 11:56:51 AM UTC+2, Daniel Arndt wrote:
>>
>> Joel,
>>
>>> [...]
>>> for (unsigned int q_index=0; q_index<n_q_points; ++q_index)
>>> for (unsigned int i=0; i<dofs_per_cell; ++i)
>>> {
>>> velocity[local_dof_indices[i]] = local_velocity_values[q_index];
>>> }
>>>
>>> Here you assign the same Tensor<1,dim> at all DoFs multiple times and
>> you end with velocity[*]=local_velocity_values[n_q_points]-1.
>> I don't think that this is what you want to do, is it? If I understand
>> you correctly, you try to assign the magnitude of the velocity in each
>> degree of freedom
>> to a different scalar Vector that represents a scalar FiniteElement
>> Vector.
>> In this case, you need to use a Quadrature object that uses the
>> unit_support_points of the scalar FE [1] and your assignment would read
>>
>> for (unsigned int i=0; i<dofs_per_cell; ++i)
>> velocity[local_dof[indices[i]] = local_velocity_values(i).norm_sqr();
>>
>> where velocity is a Vector that is related to fe_scalar and
>> local_velocity_values has the type std::vector<Vector<double> >.
>>
>> Best,
>> Daniel
>>
>> [1]
>> https://github.com/dealii/dealii/wiki/Frequently-Asked-Questions#how-to-get-the-mapped-position-of-support-points-of-my-element
>>
>
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