Barry, thanks. True and not true.
SNES can converge under other conditions, such as SNORM condition, e.g.,
Solving time step 300, using BDF1, dt = 0.1.
Current time (the starting time of this time step) = 29.85.
NL step = 0, SNES Function norm = 5.49192E-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 0
In this case, snes_rtol is ignored.
Ling
On Mon, Nov 2, 2015 at 6:29 PM, Barry Smith <[email protected]> wrote:
>
> > On Oct 30, 2015, at 12:23 PM, Zou (Non-US), Ling <[email protected]>
> wrote:
> >
> > Hi All,
> >
> > From physics point of view, I know my simulation converges if nothing
> changes any more.
> >
> > I wonder how normally you do to detect if your simulation reaches steady
> state from numerical point of view.
> > Is it a good practice to use SNES convergence as a criterion, i.e.,
> > SNES converges and it takes 0 iteration(s)
>
> Depends on the time integrator and SNES tolerance you are using. If you
> use a -snes_rtol 1.e-5 it will always try to squeeze 5 MORE digits out of
> the residual so won't take 0 iterations even if there is only a small
> change in the solution.
> >
> > Thanks,
> >
> > Ling
>
>
