[petsc-users] SNESLineSearchSetPre/PostCheck()

[Jed Brown]

"Buesing, Henrik" <hbuesing at eonerc.rwth-aachen.de> writes:

>> -----Ursprüngliche Nachricht-----
>> Von: Jed Brown [mailto:jed at jedbrown.org]
>> Gesendet: 01 December 2017 14:18
>> An: Buesing, Henrik <hbuesing at eonerc.rwth-aachen.de>; petsc-users
>> <petsc-users at mcs.anl.gov>
>> Betreff: Re: [petsc-users] SNESLineSearchSetPre/PostCheck()
>> 
>> "Buesing, Henrik" <hbuesing at eonerc.rwth-aachen.de> writes:
>> 
>> > Dear all,
>> >
>> > 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? 

You probably want to start your search in the feasible set so might as well use the precheck.