# [petsc-dev] KSP rtol

Wed Dec 14 12:45:20 CST 2011

```I have a nonlinear problem and am finding the the convergence test for the interior PETSc linear solver is apparently testing against the norm of the first linear solve (see appended).  This is clearly not what anyone would want, is this the intended semantics?  Is there perhaps a method to reset rtol?

Mark

Picard iteration 0 max(resid) = 781020
0 KSP Residual norm 2.499264167662e+07
1 KSP Residual norm 6.330915810095e+06
2 KSP Residual norm 1.856999435466e+06
3 KSP Residual norm 3.967325725053e+05
4 KSP Residual norm 9.037332775808e+04
5 KSP Residual norm 1.826960320400e+04
Linear solve converged due to CONVERGED_RTOL iterations 5
Picard iteration 1 max(resid) = 727577 ------- Rate = 1.07345
0 KSP Residual norm 6.885328126772e+06
1 KSP Residual norm 2.150319244570e+06
2 KSP Residual norm 2.297759417371e+05
3 KSP Residual norm 3.321819214451e+04
4 KSP Residual norm 4.155970071625e+03
Linear solve converged due to CONVERGED_RTOL iterations 4
Picard iteration 2 max(resid) = 486788 ------- Rate = 1.49465
0 KSP Residual norm 2.987417661953e+06
1 KSP Residual norm 5.046119985008e+05
2 KSP Residual norm 3.882757664605e+04
3 KSP Residual norm 4.106091678345e+03
Linear solve converged due to CONVERGED_RTOL iterations 3
Picard iteration 3 max(resid) = 137348 ------- Rate = 3.54418
0 KSP Residual norm 7.285359985607e+05
1 KSP Residual norm 9.132700545850e+04
2 KSP Residual norm 6.834608381922e+03
Linear solve converged due to CONVERGED_RTOL iterations 2
Picard iteration 4 max(resid) = 25082.7 ------- Rate = 5.47582
0 KSP Residual norm 1.207523847817e+05
1 KSP Residual norm 1.286174706329e+04
Linear solve converged due to CONVERGED_RTOL iterations 1
Picard iteration 5 max(resid) = 5723.21 ------- Rate = 4.38264
0 KSP Residual norm 2.211945822133e+04
Linear solve converged due to CONVERGED_RTOL iterations 0

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