[petsc-users] SNES with constraint diverges

[Josh L]

Yes, I initialize all u_i to 1.0



2018-09-11 23:37 GMT-05:00 Smith, Barry F. <bsmith at mcs.anl.gov>:

>
>    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 <ysjosh.lo at gmail.com> 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
> >
>
>
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