[petsc-users] use kspsolve repeately

[Matthew Knepley]

On Sat, Aug 24, 2013 at 6:48 AM, 丁老师 <ztdepyahoo at 163.com> wrote:

>    thank you . but the matrix element has been changed in the third and
> fourth call. how to re calculate the preconditioner.
>

Don't give SAME_PRECONDITIONER, and read the KSP section of the manual.

   Matt


>
>
> 在 2013-08-24 18:18:17，"Matthew Knepley" <knepley at gmail.com> 写道：
>
>
> On Sat, Aug 24, 2013 at 4:57 AM, 丁老师 <ztdepyahoo at 163.com> wrote:
>
>> in  my code, i need to use kspsolve in the following way
>>
>>     KSP ksp;
>>
>>     KSPCreate(PETSC_COMM_WORLD,&ksp);
>>     KSPSetOperators(ksp,A,A,SAME_NONZERO_PATTERN);
>>     KSPSetOperators(ksp,A,A,SAME_PRECONDITIONER);
>>     KSPSetInitialGuessNonzero(ksp,PETSC_TRUE)
>>      KSPSetType(ksp,KSPBCGS);
>>     KSPSetFromOptions(ksp);
>>
>>   set the matrix A value and right hand side bu and bv.
>>     kspsolve(A,bu);
>>     kspsolve(A,bv);
>>   change the value of matrix A and bu bv,
>>      kspsolve(A,bu);
>>      kspsolve(A,bv);
>>
>>  the first and second call to the kspsolve use the same preconditioner.
>> but which preconditoner does the third and fourth call to the kspsolve
>> since the value of the matrix A has changed.
>>
>
> The first call is redundant, and the subsequent solves use the same
> preconditioner, as you asked.
>
>    Matt
>
>
>>
>>
>>
>>
>>
>
>
> --
> 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
>
>
>
>


-- 
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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