[petsc-users] How to turn off preconditioner in PETSC?

Matthew Knepley knepley at gmail.com
Wed Mar 21 06:45:18 CDT 2018

On Wed, Mar 21, 2018 at 3:35 AM, 我 <dayedut123 at 163.com> wrote:

> Hi,
> I want to compare the time cost between preconditioner and
> unpreconditioner in PETSc. But I didn't know how to turn off the
> preconditioner in Petsc. If I choose the PCNONE, but the solution even can
> not converge.

That is how you turn off a preconditioner, -pc_type none. Without a
preconditioner, almost nothing converges. You can't have it both ways.



> If I do not declare PC at the beginning of my program, will PETSc choose a
> default preconditioner? I just want to turn off it. Any suggestions?
> Thank you very much!
> Daye

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.caam.rice.edu/~mk51/>
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