On Nov 25, 2013, at 6:23 AM, Lorenzo Zanon <[email protected]>
 wrote:

> Hello,
> 
> Thanks for the detailed answer!
> 
> I've just re-run the executable taking off the -snes_mf_operator and LU 
> options, but it doesn't look any better... :
> 
> Running ./example-opt -snes_type ls -snes_linesearch_type basic -ksp_rtol 1e-4
>  NL step  0, |residual|_2 = 1.936492e-05
>  NL step  1, |residual|_2 = 1.938856e-05
>  NL step  2, |residual|_2 = 1.941222e-05
>  NL step  3, |residual|_2 = 1.943592e-05
>  NL step  4, |residual|_2 = 1.945964e-05
> 
> Then I stopped it because it didn't look like converging, after one hour or 
> so.
> 

Do you need the line search? with an NL decay rate that slow one of two things 
is happening I'd bet - either the Jacobian is incorrect, so your computed dU is 
not a descent direction(see the increase from steps 2-4) or the line search is 
behaving non-optimally.

I think -snes_info (?) will present more verbose information that may be useful 
to you.

-Ben


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