[petsc-users] About Preconditioner and MUMPS

[Barry Smith]

> On Dec 6, 2022, at 5:15 AM, 김성익 <ksi2443 at gmail.com> wrote:
> 
> Hello,
> 
>  
> I have some questions about pc and mumps_icntl.
> 
> 1.     What’s the difference between adopt preconditioner by code (for example, PetscCall(PCSetType(pc,PCLU)) and option -pc_type lu??
> And also, What’s the priority between code pcsettype and option -pc_type ??
> 
> 
> 2.     When I tried to use METIS in MUMPS, I adopted metis by option (for example, -mat_mumps_icntl_7 5). In this situation, it is impossible to use metis without pc_type lu. However, in my case pc type lu makes the performance poor. So I don’t want to use lu preconditioner. How can I do this?
> 
   The package MUMPS has an option to use metis in its ordering process which can be turned on as indicated while using MUMPS.  Most preconditioners that PETSc can use do not use metis for any purpose hence there is no option to turn on its use.  For what purpose do you wish to use metis? Partitioning, ordering, ?


     
>  
> Thanks,
> 
> Hyung Kim
> 

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