> "If your goal is to replicate the matrix on every process, it might be
> easiest to create a data structure that collects all of the local
> contributions (local matrix, plus the dof indices array) and send that around
> between processes, which then all build their own matrix. That may be simpler
> than sending around the matrix because the latter is a PETSc object to which
> you don't easily have access to its internal representation."
Thank you Dr. Bangerth for this suggestion. As I am fairly new to
object oriented programing, I did not think in this light. I have a related
question.May I ask if there is a function in dealii to identify cells on the
boundaries of subdomains?
Regards,
Rahul
> On Sep 28, 2022, at 5:18 PM, Wolfgang Bangerth <[email protected]> wrote:
>
> On 9/27/22 23:50, Rahul Gopalan Ramachandran wrote:
>> Thank you for the clarification. Isend should be the way to patch this.
>> Alternatively, what is your opinion on copying the matrix to a single
>> processor (if that is possible) using MPI_Gather? Would the cell iterators
>> then no longer work? Ignoring scalability will this also be an option?
>
> At least in principle, of course, we'd like to avoid writing programs that we
> know can't scale because each process stores data replicated everywhere --
> like the entire matrix. In practice, if your goal is to run on 10 or 20
> processes, this may still work, though you should recognize that the system
> matrix is the largest object you probably have in your program (even if you
> fully distribute it).
>
> If your goal is to replicate the matrix on every process, it might be easiest
> to create a data structure that collects all of the local contributions
> (local matrix, plus the dof indices array) and send that around between
> processes, which then all build their own matrix. That may be simpler than
> sending around the matrix because the latter is a PETSc object to which you
> don't easily have access to its internal representation.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: [email protected]
> www: http://www.math.colostate.edu/~bangerth/
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