[Users] PreSync and recovery from checkpoint

[Gabriele Bozzola]

Hi Roland,

Thanks for your response, which made me realize that the conformal factor
is not
checkpointed, so the error makes perfect sense.

Also POST_RECOVER_VARIABLES only runs the scheduled function on
> timelevel 0 (ie current time) and not any past timelevels so if there
> are multiple time levels to the constraint variables, only tl=0 will be
> initialized.


In this specific case, I can either turn on checkpointing for the BSSN
variables
in ProcaEvolve, or I can recompute them from the ADM ones after recovery.
What is the correct way to re-initialize a derived variable after recovery?

Thanks,
Gabriele

On Mon, Jan 3, 2022 at 2:13 PM Roland Haas <rhaas80 at gmail.com> wrote:

> Hello Gabriele,
>
> I seem to have trouble sending email to the ET mailing list server
> using my regular UIUC email address, so maybe using GMail will work
> better.
>
> Yours,
> Roland
>
> Begin forwarded message:
>
> Date: Sat, 1 Jan 2022 10:36:00 -0500
> From: Roland Haas <rhaas at illinois.edu>
> To: Gabriele Bozzola <bozzola.gabriele at gmail.com>
> Cc: Einstein Toolkit Users <users at einsteintoolkit.org>
> Subject: Re: [Users] PreSync and recovery from checkpoint
>
>
> Hello Gabriele,
>
> > I have a fork of ProcaEvolve (
> >
> https://urldefense.com/v3/__https://bitbucket.org/Sbozzolo/proca/src/master/__;!!DZ3fjg!oMcQru84TKsWMoY2YFsLTkLW7WfZuSfD9TnxLZdhbUwY8BR_fjy2ZykIwaXVaVGa$
> )
> > where I added the READS/WRITES statements for
> > PreSync and other features. One of such features
> > is computing the constraint, but I found out that there
> > is some problem when PreSync is running with
> > `mixed-error`.
> hmm.
>
> > I have a write statement for chi in CCTK_INITIAL, which
> > is not called when restarting a simulation. Nonetheless,
> > chi should be available everywhere because it is read
> > from a checkpoint. What is the correct thing to do in
> > this scenario?
> When grid functions are read in from a checkpoint then they are marked
> as being valid everywhere. This is done in CarpetIOHDF5/src/Input.cc in
> the Recover function in the block that starts with
>
> // check that all variables have been read completely on this
> mglevel/reflevel
>
> specifically in line 793 of that file:
>
> gf->set_valid(mglevel, reflevel, tl, CCTK_VALID_EVERYWHERE);
>
> If these variables are not checkpointed (likely, given that they are
> only constraints and thus not usually considered "important" to
> checkpoint) then you would have to add code to say
> POST_RECOVER_VARIABLES to initialize them (eg to 0). This is a good
> idea to do even without considering PreSync since it avoids having
> random junk data (or poison) in the constraint output for a couple of
> steps (depending on mesh refinement details) after recovery.
>
> Something like:
>
> schedule Proca_ClearConstraints AT POST_RECOVER_VARIABLES
> {
>   LANG: Fortran
> } "Initialize constraint values after recovery"
>
> You can also try to to Proca_Constraints in post-recover variables but,
> since the constraints require derivatives and those cannot be
> (correctly) computed in post-recover-variables, the constraints for the
> checkpointed timestep will (possibly I would have to think about
> exactly how checkpointing, prolongation and time stepping
> interact) differ before and after recovery.
>
> Also POST_RECOVER_VARIABLES only runs the scheduled function on
> timelevel 0 (ie current time) and not any past timelevels so if there
> are multiple time levels to the constraint variables, only tl=0 will be
> initialized.
>
> Yours,
> Roland
>
> --
> My email is as private as my paper mail. I therefore support encrypting
> and signing email messages. Get my PGP key from http://keys.gnupg.net.
>
>
> --
> My email is as private as my paper mail. I therefore support encrypting
> and signing email messages. Get my PGP key from http://keys.gnupg.net.
>
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