[petsc-users] Using Petsc with Finite Elements Domain Decomposition

[Barry Smith]

> On Jul 12, 2016, at 4:13 AM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Tue, Jul 12, 2016 at 3:35 AM, Ivano Barletta <ibarletta at inogs.it> wrote:
> Dear Petsc users
> 
> my aim is to parallelize the solution of a linear
> system into a finite elements
> ocean model.
> 
> The model has been almost entirely parallelized, with
> a partitioning of the domain made element-wise through
> the use of Zoltan libraries, so the subdomains
> share the nodes lying on the edges.
> 
> The linear system includes node-to-node dependencies
> so my guess is that I need to create an halo surrounding 
> each subdomain, to allow connections of edge nodes with
> neighbour subdomains ones
> 
> Apart from that, my question is if Petsc accept a
> previously made partitioning (maybe taking into account of halo)
> using the data structures coming out of it
> 
> Has anybody of you ever faced a similar problem?
> 
> If all you want to do is construct a PETSc Mat and Vec for the linear system,
> just give PETSc the non-overlapping partition to create those objects. You
> can input values on off-process partitions automatically using MatSetValues()
> and VecSetValues().

  Note that by just using the VecSetValues() and MatSetValues() PETSc will manage all the halo business needed by the linear algebra system solver automatically. You don't need to provide any halo information to PETSc. It is really straightforward.

  Barry

> 
>   Thanks,
> 
>     Matt
>  
> Thanks in advance
> Ivano 
> 
> 
> 
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener