[petsc-users] fortran interface to snes matrix-free jacobian

[Jed Brown]

Then just use MatShell. I see the docs need some work to clarify this, but MatCreateSNESMF is to specify matrix-free finite differencing from code (perhaps where one wants to customize parameters).

Yi Hu <y.hu at mpie.de> writes:

> Dear Jed,
>
> Thanks for your reply. I have an analytical one to implement.
>
> Best, Yi
>
> -----Original Message-----
> From: Jed Brown <jed at jedbrown.org> 
> Sent: Wednesday, December 20, 2023 5:40 PM
> To: Yi Hu <y.hu at mpie.de>; petsc-users at mcs.anl.gov
> Subject: Re: [petsc-users] fortran interface to snes matrix-free jacobian
>
> Are you wanting an analytic matrix-free operator or one created for you based on finite differencing? If the latter, just use -snes_mf or -snes_mf_operator.
>
> https://petsc.org/release/manual/snes/#jacobian-evaluation
>
> Yi Hu <y.hu at mpie.de> writes:
>
>> Dear PETSc team,
>>  
>> My  solution scheme relies on a matrix-free jacobian in the SNES solver. I saw the useful C interface like MatCreateSNESMF(), DMSNESCreateJacobianMF(). I am wondering if you have the fortran equivalence?
>>  
>> I think for my problem in the main program I need to do DMDASNESsetJacobianLocal(DM, INSERT_VALUES, myJacobian, ctx, err_petsc). Then in myJacobian() subroutine I have to create the operator from DMSNESCreateJacobianMF(), and register my own MATOP_MULT from MatShellSetOperation(). Am I correct? 
>>  
>> Are these fortran subroutines available? I saw an example in ts module 
>> as ex22f_mf.F90 which behaves similar as what I would like to do. Because I would like to use ngmres, I then need to stay in the SNES.
>>  
>> Thanks for your help.
>>  
>> Best wishes,
>> Yi
>>
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>  
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> Please consider that invitations and e-mails of our institute are 
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> If you are not sure of the validity please contact rco at mpie.de
>
> Bitte beachten Sie, dass Einladungen zu Veranstaltungen und E-Mails
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> In Zweifelsfällen wenden Sie sich bitte an rco at mpie.de
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