[petsc-users] Distributing already assembled stiffness matrix

[Jaganathan, Srikrishna]

On 2017-10-21 00:42, Barry Smith wrote:
>> On Oct 18, 2017, at 4:14 AM, Jaganathan, Srikrishna 
>> <srikrishna.jaganathan at fau.de> wrote:
>> 
>> Hello,
>> 
>> 
>> I have been trying to distribute a already existing stiffness matrix 
>> in my FEM code to petsc parallel matrix object , but I am unable to 
>> find any documentation regarding it.
> 
>    I really really don't recommend doing this. If you code is
> sequential and you want to speed up the linear solves then use some
> linear solver library that uses OpenMP for parallelism and be done
> with it. Mix sequential finite element assembly with MPI parallel
> solvers is just not worth going within 100 meters of.
> 
>    Barry
> 
Yeah, it makes sense to not mix both. We are trying to have an MPI 
parallel Finite element assembly, but it is a quite big overhaul of the 
existing code so as a first step we are trying to incorporate the solver 
and then proceed from that.
> 
>> It was quite straightforward to create a sequential petsc matrix 
>> object and everything was working as intended.I have read some of the 
>> user comments in the mailing lists regarding similar situation and 
>> most of the times the solution suggested is to create stiffness matrix 
>> from the the mesh in distributed format. Since its a little difficult 
>> in my case to pass the mesh data in the code , is there anyway to 
>> distribute already existing stiffness matrix ?
>> 
>> Thanks and Regards
>> 
>> Srikrishna Jaganathan