[Users] recon_method dependency (weno)

[Hee Il Kim]

Hi all,

I made a minimal test of the recon method issue for the MHD code with
Bvec=0. It also shows that WENO is problematic in producing consistent
inspiralling behaviour (recon_comparison_mhd.png). The tested model is for
M_baryon = 1.4 M_solar binary with 40km separation and dxmin=0.375, studied
in Parma group's 2016 paper.

It's a totally separate issue but for your curiosity, I attached the time
series of Psi4 for l=m=2. It shows a much shorter t_merger and the poster
merger difference between MHD/HD. But it's somehow understandable and
should be examined with higher resolutions etc.

Thanks,

Hee Il

On Tue, Jun 15, 2021 at 1:20 AM Gabriele Bozzola <bozzola.gabriele at gmail.com>
wrote:

> 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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