[petsc-users] SNESLineSearchSetPre/PostCheck()

[Buesing, Henrik]

> > > So what is the difference between the pre and post check? When
> > > should
> > I use what?
> >
> > PreCheck runs before starting the line search, PostCheck runs after
> > the line search has completed and (if relevant) the inequality
> projection.
> 
> [Buesing, Henrik] What I did was using the PreCheck to change the step
> length if pressure or enthalpy went out of physical bounds (e.g. got
> negative).
> 
> Is the impact on Newton's method doing this more severe or less than
> using the PostCheck?
> 

In SNESLineSearchPostCheck: Should I update the direction with Y = W - \lambda*X, when I change W? Do I get the \lambda from the linesearch context?

Henrik