[petsc-users] rtol convergence

[Nicola Varini]

Dear all, forgive me if the following question is trivial, but I am 
trying to figure out
how the convergence criteria works in case of -ksp_norm_type preconditioned.
Below you can find the logs for preconditioned vs unpreconditioned. The 
solver converge with reason converged_rtol.
-ksp_rtol=1e-7
In the case of unpreconditioned norm it is clear that ||r||/||b||<1e-7 
at iteration 12.
In the case of preconditioned norm it should be ||r||/||b|| = 1.17e-06.
What am I missing?

*PRECONDITIONED NORM*
   0 KSP preconditioned resid norm 5.033493299009e+03 true resid norm 
3.204525251924e+02 ||r(i)||/||b|| 1.000000000000e+00
   1 KSP preconditioned resid norm 3.425803632572e+02 true resid norm 
1.937892001317e+02 ||r(i)||/||b|| 6.047360682066e-01
   2 KSP preconditioned resid norm 4.382931341126e+01 true resid norm 
5.154130142755e+01 ||r(i)||/||b|| 1.608391177339e-01
   3 KSP preconditioned resid norm 4.272202338001e+00 true resid norm 
9.790042315960e+00 ||r(i)||/||b|| 3.055067926234e-02
   4 KSP preconditioned resid norm 2.728350554402e-01 true resid norm 
1.065721671294e+00 ||r(i)||/||b|| 3.325677245496e-03
   5 KSP preconditioned resid norm 2.269929645857e-02 true resid norm 
1.475155830456e-01 ||r(i)||/||b|| 4.603352180079e-04
   6 KSP preconditioned resid norm 7.380512306491e-03 true resid norm 
4.703550871658e-02 ||r(i)||/||b|| 1.467783993536e-04
   7 KSP preconditioned resid norm 1.413199151428e-03 true resid norm 
1.452742106199e-02 ||r(i)||/||b|| 4.533408202436e-05
   8 KSP preconditioned resid norm 3.759000903215e-04 true resid norm 
4.907814057015e-03 ||r(i)||/||b|| 1.531526098622e-05

*UNPRECONDITIONED NORM*

   0 KSP unpreconditioned resid norm 3.204525251924e+02 true resid norm 
3.204525251924e+02 ||r(i)||/||b|| 1.000000000000e+00
   1 KSP unpreconditioned resid norm 1.310814475877e+02 true resid norm 
1.310814475877e+02 ||r(i)||/||b|| 4.090510677331e-01
   2 KSP unpreconditioned resid norm 2.319724277605e+01 true resid norm 
2.319724277605e+01 ||r(i)||/||b|| 7.238901538416e-02
   3 KSP unpreconditioned resid norm 2.060554152717e+00 true resid norm 
2.060554152717e+00 ||r(i)||/||b|| 6.430138603150e-03
   4 KSP unpreconditioned resid norm 2.471285360225e-01 true resid norm 
2.471285360226e-01 ||r(i)||/||b|| 7.711861090006e-04
   5 KSP unpreconditioned resid norm 6.698832182690e-02 true resid norm 
6.698832182689e-02 ||r(i)||/||b|| 2.090428895409e-04
   6 KSP unpreconditioned resid norm 1.941260318181e-02 true resid norm 
1.941260318179e-02 ||r(i)||/||b|| 6.057871808041e-05
   7 KSP unpreconditioned resid norm 5.610469571259e-03 true resid norm 
5.610469571233e-03 ||r(i)||/||b|| 1.750795868394e-05
   8 KSP unpreconditioned resid norm 1.357950031961e-03 true resid norm 
1.357950031957e-03 ||r(i)||/||b|| 4.237601283190e-06
   9 KSP unpreconditioned resid norm 4.277774357590e-04 true resid norm 
4.277774357315e-04 ||r(i)||/||b|| 1.334916725885e-06
  10 KSP unpreconditioned resid norm 1.171326258320e-04 true resid norm 
1.171326258188e-04 ||r(i)||/||b|| 3.655225551692e-07
  11 KSP unpreconditioned resid norm 3.381696730013e-05 true resid norm 
3.381696731034e-05 ||r(i)||/||b|| 1.055287902320e-07
  12 KSP unpreconditioned resid norm 8.902026754193e-06 true resid norm 
8.902026767788e-06 ||r(i)||/||b|| 2.777954944322e-08


Thanks,

Nicola

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20201125/66314955/attachment.html>