[petsc-users] snes + matrix free + coloring

[panourg at mech.upatras.gr]

What do you mean when you say that i do not use a matrix free method at all?

With matrix-free method only the operator is "free". Not the
preconditioning matrix.

For this i always set -snes_mf_operator option.

Either way is any way to have preconditioner without forming the its prec
matrix??

Panourgias Kostas




> Then you aren't using a matrix-free method at all. Just don't call
> SNESSetJacobian and it will be done for you. Are you using a DM? If not,
> you will also need to create a MatFDColoring. The easiest way to do that,
> if you don't have a structured mesh, is to assemble the nonzero pattern of
> your operator.
>
> On Wed, Oct 10, 2012 at 3:44 PM, <panourg at mech.upatras.gr> wrote:
>
>> Is exactly the same.
>>
>> Kostas
>>
>>
>>
>>
>>
>>
>> > On Wed, Oct 10, 2012 at 3:32 PM, <panourg at mech.upatras.gr> wrote:
>> >
>> >> Dear all
>> >>
>> >> I have a non-linear system which i want to solve it with matrix free
>> >> method. However i must form the whole proconditioning matrix using
>> >> finite
>> >> differences and coloring method.
>> >>
>> >
>> > How is the preconditioning matrix different from the actual operator?
>> >
>> >
>> >>
>> >> I can set the function F() of non-linear system (i take the notation
>> F()
>> >> from documentation).
>> >>
>> >> Could you send me exactly the commands and the order of it which i
>> must
>> >> use or an apt example for that?
>> >>
>> >> I have looked for that in internet but i could not find any suitable
>> >> example.
>> >>
>> >> Kostas
>> >>
>> >> Thanks
>> >>
>> >>
>> >
>>
>>
>