[petsc-users] User Defined KSP Method in Fortran

[Barry Smith]

  I think it is best to code the modified GMRES method in C; likely, much of the current GMRES code could be reused. We'd be happy to help incorporate it into PETSc.

  Barry


> On Jan 22, 2025, at 5:11 PM, Matthew Knepley <knepley at gmail.com> wrote:
> 
> On Wed, Jan 22, 2025 at 3:18 PM Frank Bramkamp <bramkamp at nsc.liu.se <mailto:bramkamp at nsc.liu.se>> wrote:
>> Dear PETSc team,
>> 
>> I was planning to program a custom KSP method, some modified GMRES.
>> We mainly use PETSc from Fortran. Therefore I wonder it is possible
>> to have an interface to a custom KSP solver that is written in fortran.
>> 
>> I thought of using KSPRegister to register my own routine, but that seems only
>> available in C.  Or is it possible to have a fortran/C wrapper to do that ?
> 
> We have wrappers for other functions that take callbacks, such as SNESSetFunction(). What
> we need to do is have a list of Fortran function pointers for this method. They when you
> register, we actually stick in a C wrapper that calls your Fortran function pointer that we have
> stored in our list. It should be straightforward looking at the implementation for something like
> SNESSetFunction(). We would help if you want to try :)
> 
> Barry, is this impacted by your binding rewrite?
> 
>   Thanks,
> 
>       Matt
>  
>> Thanks, Frank Bramkamp
>> 
>> 
>> 
>> 
>> 
> 
> 
> 
> --
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
> 
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