[petsc-users] What block size means in amg aggregation type

[Barry Smith]

  Sorry know one answered it. I had hoped Mark Adams would since he knows much more about it then me.

> On Jul 6, 2016, at 2:50 PM, Eduardo Jourdan <eduardojourdan92 at gmail.com> wrote:
> 
> Hi,
> 
> I am kind of new to algebraic multigrid methods. I tried to figure it on my own but I'm not be sure about it.
> 
> How the block size (bs) of a blocked matrix affects the AMG AGG? I mean, if bs = 4, then
> in the coarsening phase and setup, blocks of 4x4 matrix elements are considered to remain in the coarse level and a certain quantity of block neighbors are restricted and remain in the finer level? Never a row inside a block matrix is selected and the other elements of this block aren't, am I right?

   Correct 
> The entire block is interpolated when it comes to the interpolation phase?

   Correct and they all use the same interpolation.
> 
> If the original problem is not a system of equations, then bs=1?

   Yes. For a Poission operator it is 1 for linear elasticity it is 2 to 6 depending on the dimension and the model.
> 
> Thank you,
> 
> Eduardo
> 
>