[petsc-users] Regarding changes in the 3.14 release

[Matthew Knepley]

On Wed, Oct 28, 2020 at 8:57 PM Sajid Ali <sajidsyed2021 at u.northwestern.edu>
wrote:

> Hi Matt,
>
> Thanks for the clarification. The documentation
> <https://gitlab.com/petsc/petsc/-/blob/master/src/snes/interface/snes.c#L3304>
> for SNESSetLagPreconditioner states "If  -1 is used before the very first
> nonlinear solve the preconditioner is still built because there is no
> previous preconditioner to use" which was true prior to 3.14, is this
> statement no longer valid ?
>

Sounds like it is not. Barry?


> What is the difference between having -snes_lag_preconditioner -2 and
> having -snes_lag_preconditioner_persists true ?
>

Persists applies to multiple solves, whereas -2 only applies to the current
one.

  Thanks,

     Matt


> PS :  The man pages for SNESSetLagJacobianPersists should perhaps not
> state the lag preconditioner options database keys and vice versa for
> clarity.
>
> Thank You,
> Sajid Ali | PhD Candidate
> Applied Physics
> Northwestern University
> s-sajid-ali.github.io
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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