Hi Dr. Bangerth,

As a follow-up question, upon calling compress(), will the local copy of 
the system matrix on a specific processor get updated to contain 
information from all other processors? In other words, if I print out the 
system matrix from a particular processor after calling compress(), is that 
the same global system matrix that the linear solver is solving?

Thanks a lot for clarifying!


On Wednesday, July 29, 2020 at 9:55:38 AM UTC-5, Wolfgang Bangerth wrote:
> Jimmy, 
> > A minimum example to reproduce this is attached. When the mesh is built 
> using 
> > GridGenerator::hyper_cube or GridGenerator::subdivided_hyper_rectangle 
> with 
> > subsequent refinement, the program works as expected. When the same mesh 
> is 
> > generated using GridGenerator::subdivided_hyper_rectangle without any 
> > subsequent refinement, some entries in the global stiffness matrix (the 
> nodes 
> > on the right hand side of the mesh, in this case, using 2 processors) do 
> not 
> > get updated. The example output of stiffness matrices when using one and 
> two 
> > processors are also attached for reference. 
> > 
> > So my question is, is this the expected behavior of the function? If so, 
> why 
> > is that the case? 
> There is still a lot of stuff in the program that could be remove, 
> including 
> all of the comments, to make it substantially smaller and easier to 
> understand. 
> I don't know whether there is a bug, but here is a suggestion: The finite 
> element solution u_h(x) that results from the linear system should be the 
> same 
> independent of the partitioning. But the order of degrees of freedom may 
> be 
> different, and consequently the matrix may not be the same -- it should 
> only 
> be the same up to some column and row permutation. Have you verified that 
> the 
> *solution function* (not the solution vector) that results is the same 
> independent of the number of processors? 
> Best 
>   W. 
> -- 
> ------------------------------------------------------------------------ 
> Wolfgang Bangerth          email:                 bang...@colostate.edu 
> <javascript:> 
>                             www: http://www.math.colostate.edu/~bangerth/ 

The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see 
You received this message because you are subscribed to the Google Groups 
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to dealii+unsubscr...@googlegroups.com.
To view this discussion on the web visit 

Reply via email to