[petsc-users] snes linesearch bt vs basic?

[Jed Brown]

Xiangdong <epscodes at gmail.com> writes:
> Actually my problem is not that ill-conditioned. Here is my situation. Let
> us say at time step n the snes_linesearch_basic failed. I have at least two
> options now: i) cut the dt immediately, ii) switch to snes_linesearch_bt
> with the same dt. Sometimes, switching to a different linesearch method
> without cutting dt will make snes converge, but sometimes not (then I need
> to cut dt, which is bad since more nonlinear iterations were wasted). Based
> on what you mentioned, it is impossible to decide which option is good and
> I just need to simply pick one.

There's no automatic rule to do the right thing.  If you think you can
be smart about it (perhaps using problem-specific information), you can
implement your own SNESLineSearch (it's a plugin system meant to do
this) that calls the BT versus Basic implementations (or your own,
etc.).  If you develop a new line search that is better, you can publish
a paper and contribute your code so that others can use it.  Have fun.
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