[petsc-users] help needed for -snes_mf_operator

[Dominik Szczerba]

> Start by comparing residuals, with an without. Is SNES 0 the same? Is KSP 0
> the same? KSP 1?

BCGS, with the option:

  0 SNES Function norm 1.747536282885e+01
  0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm
1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00
  1 KSP unpreconditioned resid norm 6.112827145626e-01 true resid norm
1.751036369876e+01 ||r(i)||/||b|| 1.002002869425e+00

BCGS, without:

  0 SNES Function norm 1.747536282885e+01
  0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm
1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00
  1 KSP unpreconditioned resid norm 2.930616102426e-01 true resid norm
2.930616102426e-01 ||r(i)||/||b|| 1.676998715922e-02

GMRES, with the option:

  0 SNES Function norm 1.747536282885e+01
  0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm
1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00
  1 KSP unpreconditioned resid norm 6.122286256494e-01 true resid norm
1.747536251439e+01 ||r(i)||/||b|| 9.999999820055e-01

GMRES, without:

  0 SNES Function norm 1.747536282885e+01
  0 KSP unpreconditioned resid norm 1.747536282885e+01 true resid norm
1.747536282885e+01 ||r(i)||/||b|| 1.000000000000e+00
  1 KSP unpreconditioned resid norm 6.122286294217e-01 true resid norm
6.122286294218e-01 ||r(i)||/||b|| 3.503381505824e-02

Dominik