[petsc-users] How to introduce external iterative solver into PETSc

[Matthew Knepley]

On Mon, Dec 5, 2022 at 3:08 AM 袁煕 <yuanxi at advancesoft.jp> wrote:

> Dear PETSc developers,
>
> I have my own linear solver and am trying to put it into PETSc as an
> external solver.  Following the implementation of mumps, mkl_cpardiso,
> supelu etc, I think I should do the follow:
>
> 1.  Add my solver name into MatSolverType.
> 2.  Register my solver by calling MatSolverTypeRegister
>
> to let petsc record the existence of a new solver. The problem is that the
> above external solvers are all direct solvers, and a MatFactorType
> parameter should be set to indicate its factorization type, such as LU, QR,
> or Cholesky. But my solver is an iterative one, that means I cannot specify
> its MatFactorType. I wish to understand
>
> 1. Am I doing it the right way? And if so
> 2. How to set such parameters as MatFactorType,
> lufactorsymbolic, lufactornumeric.
>

This was a misunderstanding. If it is an iterative solver, you can follow
the template for Jacobi:


https://gitlab.com/petsc/petsc/-/blob/main/src/ksp/pc/impls/jacobi/jacobi.c

There are comments throughout this file showing you how to register your
own preconditioner. You should not need to alter PETSc source.
I have done this myself with the BAMG preconditioner.

  Thanks,

      Matt


> Many thanks,
>
> Yuan
> Ph.D. in Solid Mechanics
>


-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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