[petsc-users] -ksp_pc_side for -pc_fieldsplit_schur_fact_type upper

[Barry Smith]

   Based on my reading of the attached paper, in particular the last line on page 1050 I don't think it matters.

and P−1A and AP−1 have the minimal polynomial (λ − 1)2.

since the application on either side matches the same polynomial.


  Barry

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> On Jun 23, 2017, at 11:48 AM, Hoang Giang Bui <hgbk2008 at gmail.com> wrote:
> 
> Hello
> 
> I just want to make sure that I understand the right thing, in the manual page of PCFieldSplitSetSchurFactType:   http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCFieldSplitSetSchurFactType.html
> 
> The "upper" option uses DU from the full factorization. If I understand correctly, the ksp must be used with right preconditioning, because A P^-1 = (LDU) * (DU)^(-1) = L. If that was the case, should the manual put this information to be more clear?
> 
> Thanks
> Giang
>