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

dayedut123 at 163.com
Wed Mar 21 08:07:14 CDT 2018

Thanks for your reply! You mean the preconditioner must be the necessary choice for the linear iterative method in PETSc? And the default preconditioner in PETSC is which one? I want to compare them in order to illustrate that PCHYPRE is best one for my problem. If I want to get the matrix after preconditioned (e.g. PAx=Pb, and I want to get PA), is there a function in PETSc?
Thanks again!

At 2018-03-21 18:45:18, "Matthew Knepley" <knepley at gmail.com> wrote:

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

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!



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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20180321/f86af319/attachment.html>

More information about the petsc-users mailing list