[petsc-users] odd SNES behavior

[Mark F. Adams]

> 
> 
>   You can run with -snes_linesearch_monitor also (my guess is that it is being triggered more with gamg hence more function evaluations).


snes_linesearch_monitor did not seem to tell me much (see appended).  The GAMG and HYPRE output was similar (as one would hope).  Should I  perhaps run something like '-info snes' to see where these guys diverge?

GAMG:

    4 KSP Residual norm 8.240636524364e+02
    5 KSP Residual norm 6.859873473208e+02
    6 KSP Residual norm 6.187746494615e+02
    7 KSP Residual norm 5.378415356008e+02
  Linear solve converged due to CONVERGED_RTOL iterations 7
      Line search: Using full step: fnorm 2.835772370452e+05 gnorm 4.895281520389e+04
  9 SNES Function norm 4.895281520389e+04
    0 KSP Residual norm 4.895281520389e+04
    1 KSP Residual norm 3.145172880926e+03
    2 KSP Residual norm 7.147989028232e+02
    3 KSP Residual norm 4.982303798687e+02
    4 KSP Residual norm 4.405892793165e+02
    5 KSP Residual norm 4.003228476498e+02
    6 KSP Residual norm 3.299993998722e+02
    7 KSP Residual norm 2.203595473306e+02
    8 KSP Residual norm 1.293543888554e+02
    9 KSP Residual norm 8.203517750619e+01
  Linear solve converged due to CONVERGED_RTOL iterations 9
      Line search: Using full step: fnorm 4.895281520389e+04 gnorm 8.668206596295e+03
 10 SNES Function norm 8.668206596295e+03
    0 KSP Residual norm 8.668206596295e+03
    1 KSP Residual norm 4.557232270362e+02
    2 KSP Residual norm 8.211391243357e+01
    3 KSP Residual norm 6.017999632904e+01
    4 KSP Residual norm 5.160935079494e+01
    5 KSP Residual norm 4.575984742586e+01
    6 KSP Residual norm 3.965459823946e+01
    7 KSP Residual norm 3.314109315152e+01
    8 KSP Residual norm 2.564475175103e+01
    9 KSP Residual norm 1.764923610559e+01
   10 KSP Residual norm 1.267831683136e+01
  Linear solve converged due to CONVERGED_RTOL iterations 10
      Line search: Using full step: fnorm 8.668206596295e+03 gnorm 1.763432524435e+02
 11 SNES Function norm 1.763432524435e+02
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 11


HYPRE:

    5 KSP Residual norm 3.110704123273e+03
    6 KSP Residual norm 1.609993784143e+03
    7 KSP Residual norm 8.500755950825e+02
    8 KSP Residual norm 5.335192138320e+02
  Linear solve converged due to CONVERGED_RTOL iterations 8
      Line search: Using full step: fnorm 2.796443368363e+05 gnorm 4.819210383260e+04
  9 SNES Function norm 4.819210383260e+04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 9