You have too tight a convergence tolerance for your problem. You can't
expect to get more than 1.e-12 as the minimum residual norm or even less.
How close is your solution to 1 and -1?
If you really need much higher convergence you can try ./configure
--with-precision=__float128
Barry
> On Sep 11, 2018, at 11:53 PM, Josh L <[email protected]> wrote:
>
> Yes, I initialize all u_i to 1.0
>
>
>
> 2018-09-11 23:37 GMT-05:00 Smith, Barry F. <[email protected]>:
>
> Do you start with initial conditions of 0 <= u_i <= 1 ?
>
> Run with -snes_monitor -snes_converged_reason -ksp_monitor_true_residual
> -info -snes_linesearch_monitor and send all the output
>
> Barry
>
>
> > On Sep 11, 2018, at 11:33 PM, Josh L <[email protected]> wrote:
> >
> > Hi,
> >
> > I am using SNES to solve an nonlinear equation f(u), and I know all the u_i
> > should be 0 and 1.
> >
> > First, I use SNES without constraint, and it converges.
> >
> > But, If I set
> > SNESSetType(snes,SNESVINEWTONRSLS,ierr)
> > SNESVISetVariableBounds(snes,xl,xu,ierr)
> >
> > where xl and xu is vector, and xl_i=0 and xu_i=1
> >
> > then SNES fails to converge, because linesearch fails(snes reason = -6),
> > and the norm of residual is not reducing(the norm of incremental solution
> > is reducing)
> >
> > The reason to add constraint is that I want to implement some
> > irreversibility.
> >
> >
> > Thanks,
> > Josh
> >
>
>
