[petsc-users] Motivation for default KSP solver and PC

[Barry Smith]

> On Sep 21, 2020, at 7:51 AM, Luciano Siqueira <luciano.siqueira at usp.br> wrote:
> 
> Hi *,
> 
> I'm experimenting with different combinations of KSP solvers and PCs and I don't know why GMRES/bjacobi are the default choices for CPU and GMRES/icc are the default choices for GPU. Does anyone know the reason for that?
> 

   The intention is that it is the same default, and shouldn't depend on CPU/GPU.  It is GMRES + block Jacobi (with one block per MPI rank; if there is only 1 MPI rank the block Jacobi drops out) + incomplete Cholesky or LU depending on if the matrix is marked by the users as symmetric.

   Please let us know if we have any error.

  Barry

> Thanks,
> Luciano.