PETSc convergence criteria

[Matthew Knepley]

You are using the preconditioned norm for the convergence test. You can use

KSPSetNormType(ksp,  KSP_NORM_UNPRECONDITIONED)

However, this will not work for all KSP types.

   Matt

On Wed, Aug 27, 2008 at 1:23 PM, Nguyen, Hung V ERDC-ITL-MS
<Hung.V.Nguyen at usace.army.mil> wrote:
> All,
>
> We run a test case with  -ksp_rtol 1.0e-15 and -ksp_max_it 50000. Then we
> compute the infinity and 2 norms of |a * xsolution -b| and the results are
> below. Why are these values of norms in a range 10e-8 to 10e-10 while
> -ksp_rtol is set 1.0e-15? What is the PETSc convergence criteria for the
> matrix solver?
>
> Thank you in advance,
>
> -Hung
>
>> hvnguyen:jade20% aprun -n 16 ./fw -ksp_type cg -pc_type bjacobi
>> -ksp_rtol 1.0e-15 -ksp_max_it 50000
>>  Time in PETSc solver =   0.7661848068237305       sec
>>  Computed solution - 2 norm of the residual error =
>> 1.0662412498046400E-008
>>  Computed solution - maximum residual error (infinity norm) =
>>    5.2750692702829838E-010
>>  Number of Krylov iterations =          257
>> Application 281373 resources: utime 0, stime 0
>
>



-- 
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