[petsc-users] Determine the positive definiteness

[w_ang_temp]

Yes, it isanecessarybutnotsufficientcondition.

At 2013-01-11 03:56:25,"Barry Smith" <bsmith at mcs.anl.gov> wrote:
>
>   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
>
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