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

[我]

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!
Daye






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:

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.


  Thanks,


     Matt
 
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/
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