[petsc-users] What could be the reason for a convergence history like this one?

Tue Feb 9 12:21:22 CST 2010

Hi,

The SNES convergence history shows the residual increases or stop  
decreasing starting at some iteration. I ran two different cases for  
the same code, and the history looks similar, what could be wrong with  
the code?

Thanks very much!

Case 1:
   0 SNES Function norm 9.593111354483e-01
   1 SNES Function norm 1.233321371555e-01
   2 SNES Function norm 2.926382110614e-02
   3 SNES Function norm 2.091318748212e-02
   4 SNES Function norm 1.047907743570e-02
   5 SNES Function norm 4.462043675959e-03
   6 SNES Function norm 1.851050848655e-03
   7 SNES Function norm 4.417550480988e-04
   8 SNES Function norm 1.736388356513e-04
   9 SNES Function norm 6.300414578098e-05
  10 SNES Function norm 1.929829710585e-05
  11 SNES Function norm 1.506367625001e-05
  12 SNES Function norm 1.480567720594e-05
  13 SNES Function norm 1.470754287980e-05
  14 SNES Function norm 1.461728595512e-05
  15 SNES Function norm 1.453616609384e-05
  16 SNES Function norm 1.441040320141e-05
  17 SNES Function norm 1.402352953635e-05
  18 SNES Function norm 1.343005745899e-05
  19 SNES Function norm 1.328043697395e-05
  20 SNES Function norm 1.327501784736e-05
  21 SNES Function norm 1.327431008405e-05
  22 SNES Function norm 1.327343169426e-05
  23 SNES Function norm 1.327273768560e-05
  24 SNES Function norm 1.327185496127e-05
  25 SNES Function norm 1.327119625499e-05
  26 SNES Function norm 1.327071509157e-05
  27 SNES Function norm 1.327038695378e-05
  28 SNES Function norm 1.326990549326e-05
  29 SNES Function norm 1.326917602672e-05
  30 SNES Function norm 1.326830723835e-05
  31 SNES Function norm 1.326796002362e-05
  32 SNES Function norm 1.326777827731e-05
  33 SNES Function norm 1.326755622116e-05
  34 SNES Function norm 1.326732752144e-05
  35 SNES Function norm 1.326698050145e-05
  36 SNES Function norm 1.326640877572e-05
  37 SNES Function norm 1.326587074902e-05
  38 SNES Function norm 1.326573931166e-05
  39 SNES Function norm 1.326564241601e-05
  40 SNES Function norm 1.326548432075e-05
  41 SNES Function norm 1.326531590041e-05
  42 SNES Function norm 1.326531590043e-05
  43 SNES Function norm 1.326531590045e-05
  44 SNES Function norm 1.326531590044e-05
  45 SNES Function norm 1.326531590044e-05
  46 SNES Function norm 1.326531590043e-05
  47 SNES Function norm 1.326531590045e-05
  48 SNES Function norm 1.326531590044e-05
  49 SNES Function norm 1.326531590046e-05
  50 SNES Function norm 1.326531590046e-05
Nonlinear solve did not converge due to DIVERGED_MAX_IT

case 2:
   0 SNES Function norm 1.489006328086e+00
   1 SNES Function norm 1.044141602147e-01
   2 SNES Function norm 2.662563646189e-02
   3 SNES Function norm 5.764005178654e-03
   4 SNES Function norm 2.493444656346e-03
   5 SNES Function norm 5.180475798178e-04
   6 SNES Function norm 4.166251801170e-04
   7 SNES Function norm 3.066582000814e-04
   8 SNES Function norm 2.189666367666e-04
   9 SNES Function norm 1.354684191244e-04
  10 SNES Function norm 1.287520392923e-04
  11 SNES Function norm 1.286080621054e-04
  12 SNES Function norm 1.285437650356e-04
  13 SNES Function norm 1.284168806812e-04
  14 SNES Function norm 1.283833115348e-04
  15 SNES Function norm 1.283700090330e-04
  16 SNES Function norm 1.283691578788e-04
  17 SNES Function norm 1.283486627334e-04
  18 SNES Function norm 1.283349991927e-04
  19 SNES Function norm 1.283332060308e-04
  20 SNES Function norm 1.283026682165e-04
  21 SNES Function norm 1.282981662835e-04
  22 SNES Function norm 1.282944044720e-04
  23 SNES Function norm 1.282831861627e-04
  24 SNES Function norm 1.282754274487e-04
  25 SNES Function norm 1.282754274487e-04
  26 SNES Function norm 1.282754274487e-04
  27 SNES Function norm 1.282754274487e-04
  28 SNES Function norm 1.282754274487e-04
  29 SNES Function norm 1.282754274487e-04
  30 SNES Function norm 1.282754274487e-04
  31 SNES Function norm 1.282754274487e-04
  32 SNES Function norm 1.282754274487e-04
  33 SNES Function norm 1.282754274487e-04
  34 SNES Function norm 1.282754274487e-04
  35 SNES Function norm 1.282754274487e-04
  36 SNES Function norm 1.282754274487e-04
  37 SNES Function norm 1.282754274487e-04
  38 SNES Function norm 1.282754274487e-04
  39 SNES Function norm 1.282754274487e-04
  40 SNES Function norm 1.282754274487e-04
  41 SNES Function norm 1.282754274487e-04
  42 SNES Function norm 1.282754274487e-04
  43 SNES Function norm 1.282754274487e-04
  44 SNES Function norm 1.282754274487e-04
  45 SNES Function norm 1.282754274487e-04
  46 SNES Function norm 1.282754274487e-04
  47 SNES Function norm 1.282754274487e-04
  48 SNES Function norm 1.282754274487e-04
  49 SNES Function norm 1.282754274487e-04
  50 SNES Function norm 1.282754274487e-04

Thanks a lot!

-- 
(Rebecca) Xuefei YUAN
Department of Applied Physics and Applied Mathematics
Columbia University
Tel:917-399-8032
www.columbia.edu/~xy2102