On 7/23/19 2:46 PM, 'Maxi Miller' via deal.II User Group wrote:
> I took a look at your (incomplete) step-58, which (as far as I could
> understand) solves the equation, but without propagating it in space, just in
> time. I would like to propagate the result in time and accordingly in space,
>
Thus I intended to use a GMG-preconditioner, with a Chebyshev-smoother.
Usually the GMG-preconditioner does not require the main matrix either
(yes, small matrices are still required, but they do not require the same
amount of storage space), but here I run into the problem which is
mentioned i
On 7/24/19 12:23 PM, 'Maxi Miller' via deal.II User Group wrote:
> My LinearOperator only provides a vmult-interface, nothing else, but for
> initializing the preconditioner I still need a sparse matrix, thus I can not
> use the LinearOperator, as far as I understand. Or is there a way to use it?
My LinearOperator only provides a vmult-interface, nothing else, but for
initializing the preconditioner I still need a sparse matrix, thus I can
not use the LinearOperator, as far as I understand. Or is there a way to
use it?
Am Mittwoch, 24. Juli 2019 17:28:14 UTC+2 schrieb Daniel Arndt:
>
>
Hei,
based on what I know from literature a GMG-preconditioner with Chebyshev
smoothing should work rather well for my case, thus I intended to follow
example 37 here. If I can set v_i to 1 for calculating the diagonal, that
would simplify the problem quite a lot.
The main reason for testing the
Hello everyone!
This is deal.II newsletter #88.
It automatically reports recently merged features and discussions about the
deal.II finite element library.
## Below you find a list of recently proposed or merged features:
#8411: Link to more resources on learning how to program. (proposed by
Dear Maxi,
There is not really a simple answer to your request: It depends on how
good a preconditioner you need. Matrix-free methods work best if you can
use simple preconditioners in the sense that they only need some matrix
entries (if any) and the matrix-vector product (or operator evaluation
>
> Is there then a way to use LinearOperator as Input for a preconditioner?
> Else I still have to form the full system matrix (which I would like to
> avoid).
>
Most precoditioners require access to individual matrx entries. If the
class you derive from linear operator provides a suitable in
I am currently trying to implement the JFNK-method in the matrix-free
framework (by following step-37 and step-59) for solving nonlinear
equations of the form F(u)=0. The method itself replaces the multiplication
of the explicit jacobian J with the krylov vector v during solving with the
approx
Is there then a way to use LinearOperator as Input for a preconditioner?
Else I still have to form the full system matrix (which I would like to
avoid).
Am Mittwoch, 24. Juli 2019 13:43:09 UTC+2 schrieb Daniel Arndt:
>
> On the other hand, would it be sufficient to unroll the
residual-calc
>
> On the other hand, would it be sufficient to unroll the
>>> residual-calculation, i.e. if the residual is F(u) = nabla^2 u + f, to
>>> write (in the cell-loop): (nabla^2(u + eps*src) + f - nabla^2u -
>>> f)/epsilon? Or would that lead to wrong results?
>>>
>>
>> It is sufficient to only c
Am Mittwoch, 24. Juli 2019 00:39:14 UTC+2 schrieb Daniel Arndt:
>
> Maxi,
>
> No, that code is the vmult-call I am using in my LinearOperator (and is
>> used directly in my solve()-call). The calculate_residual()-function is
>> similar to the function in step-15, with the difference, that I do
12 matches
Mail list logo
