[petsc-users] Determine the positive definiteness

[Barry Smith]

   If cg says indefinite then it is indefinite
   if cg runs and does not say it is indefinite it may still be indefinite (though probably not all that likely).

   Barry

On Jan 10, 2013, at 11:46 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Thu, Jan 10, 2013 at 10:44 AM, w_ang_temp <w_ang_temp at 163.com> wrote:
> Hello,
> 
>     I want to determine the positive definiteness. So I want to know
> 
> if it is a right way.
> 
>     I use "-ksp_type cg -pc_type none". You know, CG does not work for
> 
> indefinite matrices. I get "Linear solve did not converge due to
> 
> DIVERGED_INDEFINITE_MAT". From the information, I think it is indefinite.
> 
> Is it a right way?
> 
> 
> Its not full proof, but it could be a diagnostic.
> 
>   Matt
>  
>     Thanks.
> 
>                                             Jim
> 
> 
> 
> 
> 
> 
> -- 
> 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