[petsc-users] PETSc usage issues

[Matthew Knepley]

On Wed, Sep 28, 2022 at 2:27 PM wangzj997 <wangzj997 at foxmail.com> wrote:

> Dear PETSc development team：
>
> Currently, I am learning and trying to use PETSc's KSP to solve
> large-scale sparse linear systems Ax= b, where A is symmetric positive
> definite
>

How do you know it is positive definite? This is unusual when you have 0 on
the diagonal.

Preconditioners depend sensitively on the matrix properties. Is this a
discretization of some operator?

  Thanks,

      Matt


> and nonsingular. However, the main diagonal of A contains many 0 items,
> which leads to the fact that many preconditioners cannot be used when using
> MPI for multi-process solution, and the number of iterations is large, and
> the convergence is slow. May I ask how to solve this problem? If it is
> necessary to make the main diagonal of A all non-zero items, is there any
> solution in PETSc?
>
> I would be grateful if you would reply and answer my question.
>
> Best Regards.
>
>
>
>

-- 
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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