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

[Barry Smith]

   I apologize; please ignore my answer below. Use MatCreateShell() as indicated by Jed.


> On Dec 20, 2023, at 2:14 PM, Barry Smith <bsmith at petsc.dev> wrote:
> 
> 
> 
>> On Dec 20, 2023, at 11:44 AM, Yi Hu <y.hu at mpie.de> wrote:
>> 
>> 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?
> 
>   You can use DMSNESCreateJacobianMF() (MatCreateSNESMF is not appropriate when you are providing the operation).
> 
> 
>>> 
>>> 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?
> 
> Not exactly. Do not use DMDASNESsetJacobianLocal() use DMSNESCreateJacobianMF() to create a Mat J where you create the SNES and use SNESSetJacobian()  and pass the J matrix in along with myJacobian().
> 
>>> 
>>> 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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>> 
>> -------------------------------------------------
>> Stay up to date and follow us on LinkedIn, Twitter and YouTube.
>> 
>> Max-Planck-Institut für Eisenforschung GmbH
>> Max-Planck-Straße 1
>> D-40237 Düsseldorf
>> 
>> Handelsregister B 2533 
>> Amtsgericht Düsseldorf
>> 
>> Geschäftsführung
>> Prof. Dr. Gerhard Dehm
>> Prof. Dr. Jörg Neugebauer
>> Prof. Dr. Dierk Raabe
>> Dr. Kai de Weldige
>> 
>> Ust.-Id.-Nr.: DE 11 93 58 514 
>> Steuernummer: 105 5891 1000
>> 
>> 
>> Please consider that invitations and e-mails of our institute are 
>> only valid if they end with …@mpie.de. 
>> If you are not sure of the validity please contact rco at mpie.de
>> 
>> Bitte beachten Sie, dass Einladungen zu Veranstaltungen und E-Mails
>> aus unserem Haus nur mit der Endung …@mpie.de gültig sind. 
>> In Zweifelsfällen wenden Sie sich bitte an rco at mpie.de
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