Hello
As I become familiar with PETSc, I make a conclusion about the question
and hope that it is right.
In order to get satisfactory results when solving a linear system with
KSP, the Krylov space methods
are typically used in conjunction with a preconditioner. So the user should
select the effective Krylov
method(such as cg) and preconditioner(such as jacobi) for this linear system
Ax=b. Or it maybe not
convergence.
Thanks.
Jim
>At 2012-05-26 23:05:26,w_ang_temp <w_ang_temp at 163.com> wrote:
>Hello, Matt
> The results of the parallel and the serial are identical by the
> "-ksp_rtol 1.0e-15 -ksp_converged_reason -ksp_monitor_true_residual".
> I will make a carefulanalysis of these parameters next day because it is
> late night here now.
> Thanks again. Jim
>? 2012-05-26 22:26:20?"Matthew Knepley" <knepley at gmail.com> ???
>On Sat, May 26, 2012 at 2:22 PM, w_ang_temp <w_ang_temp at 163.com> wrote:
>Hello,Matt
> Thanks again.
> What you said("Use -ksp_type preonly -pc_type lu") means that I should use
> a direct solver.And I am puzzled.
>Okay, you want to remove variables from the investigation. You say there is a
>difference between
>the parallel and serial solve. We do this all the time, so it is not a bug. It
>is an issue of understanding.
>First, take away the tolerance issues:
> -ksp_rtol 1.0e-15 -ksp_converged_reason -ksp_monitor_true_residual
>and send output of the serial and parallel run.
> Matt
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