PETSc convergence criteria

[Nguyen, Hung V ERDC-ITL-MS]

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