[Users] recon_method dependency (weno)

[Gabriele Bozzola]

Hello,

two years ago I performed a convergence test of GRHydro.
I found that the PPM scheme converges, but not the WENO one.
Difficult to say what version of ET I used, but I'd guess the last one
of 2018.

I dug up the two attached plots. This was with a piecewise polytrope,
but the result is the same with a single polytrope. You can clearly
see how increasing the resolution does not decrease the amplitude
of the oscillation of rho in the case of WENO, but it does so in the case
of PPM. The initial data is a TOV star and no magnetic fields were used.
I don't have the par files anymore.

I didn't investigate much further because I use IllinoisGRMHD and it
is possible that I was doing something wrong. However, this conversation is
giving support to the idea that WENO might have problems.

Gabriele

On Thu, Jun 10, 2021 at 2:52 PM Hee Il Kim <heeilkim at gmail.com> wrote:

> Thanks Roland and Maria
>
> 2021년 6월 10일 (목) 오후 11:50, Roland Haas <rhaas at illinois.edu>님이 작성:
>
>> Hello Hee Il,
>>
>> from your email it seems that you are seeing differences between
>> different ET releases but with the same par file.
>>
>
> I'm not seeing different results between Turing and Lorentz. Since they
> are identical, I've shown only representative plots (rhomax vs time btw).
> The issue is that he WENO of the ET versions do not produce the same
> inspiraling time with that of WENO-Z, MP5, and PPM, whereas the other three
> recon methods show decent coincidence for the inspiralling time.
>
>
>> Yet your plot seems to not show any pair of curves that only differ by
>> the release code used.
>>
>
> Explained above.
>
>
>>
>> If you are comparing to the runs by the Parma group (or any
>> simulation) then you must ensure that you are comparing "apples with
>> apples" ie you would have to run their parfiles with the current ET
>> release (to check for a change) and also with their code (to check if
>> the issue is compiler / cluster changes).
>>
>>
> I'm not going to compare my current results to the Parma group runs. As
> you discussed in the meeting, since they used the recon codes and Con2Prim
> for the MHD, it might give different results. But if the differences are
> big even with zero B, I think it needs to be examined further in the future.
>
>
>> They provide their code and parfiles in:
>>
>> https://einstein.pr.infn.it/svn/numrel/pub/
>>
>> See "Background material" on
>>
>> https://einstein.pr.infn.it/gravity/Research/BNS2016.html
>>
>> which is listed on the "Additional Resources" page of:
>>
>> https://docs.einsteintoolkit.org/et-docs/Additional_resources
>>
>> Yours,
>> Roland
>>
>
> I've been aware of it and used its grid setup. At first, I didn't follow
> their parfile but used my own grid amr with NSTracker. But for the
> comparison, I followed the parfiles there. I haven't tried to use the
> entire code of the Parma group. But at least I found their Lorene is
> different from official Lorene and ET Lorenes. I've made an ID by using
> their Lorene but the ID was not readable by recent ET/GRHydros.
>
> My feeling is that GRHydro_WenoRecontruct codes need to be examined.
>
> Thanks,
>
> Hee Il
>
>
>> > Hi
>> >
>> > I'm reporting on recon_method dependency issue at least found in Turing
>> and
>> > Lorentz. I've been studying BNS evolution by taking some of the Parma
>> group
>> > models as references (DOI: 10.1103/PhysRevD.93.064047). But there were
>> > significant differences in merger time, t_merger. At the moment, I will
>> put
>> > aside direct comparison between the GRHydro of Parma and recents ones.
>> >
>> > What I've found is that WENO of Turing/Lorentz produces much shorter
>> > inspiraling time (See the attached figure). But WENO-Z/PPM/MP5, they all
>> > produce similar inspiraling time. Of course, depending on resolutions,
>> they
>> > produce different merging behaviour but as shown in the figure,
>> higher-res
>> > PPM matches with lower-res WENO-Z nicely, which is consistent with our
>> > expectations. I've got the identical results for both Turing and Lorentz
>> > versions.
>> >
>> > I've missed recent GRHydro developments for a long time and I have no
>> > guesses for the discrepancy. I hope GRHydro developers examine this
>> issue
>> > for the consistency of the recon_method. Thanks for your help in
>> advance.
>> >
>> > Hee Il
>>
>>
>> --
>> My email is as private as my paper mail. I therefore support encrypting
>> and signing email messages. Get my PGP key from http://pgp.mit.edu .
>>
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