[Users] Question about IllinoisGRMHD C2P failure and kuibit Psi4 extraction

Fri Jul 3 05:10:37 CDT 2026

Dear Jordan

Thank you for your quick response.

I understand what I should do. I will wait for feedback from the others, and I consider attending the weekly meeting.

Thank you again for your advice.

Best regards,

Taiki Makino
Graduate School of Science, Nagoya University
makino.taiki.g6 at s.mail.nagoya-u.ac.jp<mailto:makino.taiki.g6 at s.mail.nagoya-u.ac.jp>

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差出人: Jordan Nicoules <jnicoules at ua.pt>
日付: 金曜日, 2026年7月3日 18:38
宛先: MAKINO Taiki <makino.taiki.g6 at s.mail.nagoya-u.ac.jp>
CC: users at einsteintoolkit.org <users at einsteintoolkit.org>
件名: Re: Question about IllinoisGRMHD C2P failure and kuibit Psi4 extraction

Hi Taiki,

(apologies for my previous typo)

The next step would be to understand why the simulation crashes and doesn't go past t=0. This is beyond what I can quickly hotfix I think, so I'm calling to other members to answer that. Potentially, if you have the chance, the weekly calls can also be an opportunity to interact with people directly and put forth your questions.

Regarding files that have more than one line of data, that would make sense for the 1D profiles, but they still probably only correspond to iteration 0 (t=0).

Best,

Jordan

________________________________
From: MAKINO Taiki <makino.taiki.g6 at s.mail.nagoya-u.ac.jp>
Sent: Friday, July 3, 2026 10:14:57 AM
To: Jordan Nicoules
Cc: users at einsteintoolkit.org
Subject: Re: Question about IllinoisGRMHD C2P failure and kuibit Psi4 extraction

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Dear Jordan

Thank you for your response.

When I checked the result of my simulation, SimDir.gws[100][(2,2)].x was indeed 0 as you said and the simulation stopped at iteration=0.

Also, I checked the psi4 ASCII files and all of them contained only one line. (However, the ASCII files that do not contain information of psi4 have several lines of data.)

I am not sure what is causing this. What should I do next ?

Best regards,

Taiki Makino

Graduate School of Science, Nagoya University

makino.taiki.g6 at s.mail.nagoya-u.ac.jp<mailto:makino.taiki.g6 at s.mail.nagoya-u.ac.jp>

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差出人: Jordan Nicoules <jnicoules at ua.pt>
日付: 木曜日, 2026年7月2日 19:31
宛先: MAKINO Taiki <makino.taiki.g6 at s.mail.nagoya-u.ac.jp>; users at einsteintoolkit.org <users at einsteintoolkit.org>
件名: Re: Question about IllinoisGRMHD C2P failure and kuibit Psi4 extraction

Hi Taiko,

I will (partly) skip the first part of your message and let others reply on that, as I don't have experience with NS simulations.

Regarding the gravitational wave extraction, I think you are accessing the data correctly (your example gives the time series for one mode at one radius), and there should be more than one element in general. From your parameter file, it seems the output should go to an ascii file (it's the default), so you can double check in that file too.

However, since you have `Multipole::out_every = 128`, does your simulation reach iteration 128 and later? In particular, because you're getting nans at iteration 0, does the simulation actually go past t=0? Given what you're saying, I guess your single element of `SimDir.gws[100][(2,2)].x` is 0 (i.e t=0).

Best,

Jordan

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From: Users <users-bounces at einsteintoolkit.org> on behalf of MAKINO Taiki via Users <users at einsteintoolkit.org>
Sent: Thursday, July 2, 2026 12:39:00 AM
To: users at einsteintoolkit.org
Subject: [Users] Question about IllinoisGRMHD C2P failure and kuibit Psi4 extraction

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Dear Einstein Toolkit Users,

I am a new Einstein Toolkit user, and I have some questions about a BNS simulation.

I am trying to run a BNS simulation using bns.par, which I downloaded from Einstein Toolkit Gallery (https://einsteintoolkit.org/gallery/bns/index.html) and slightly modified.

I can successfully create and submit the simulation but the following message appears during the simulation:

INFO (IllinoisGRMHD): C2P: Iter. # 0, Lev: 5 NumPts= 132300 | Backups: 0 0 0 | Fixes: VL= 0 rho*= 0 Averaged pts = 38250 Font1D 38250 | Failures: 2250 InHoriz= 0 / 0 | 1.00 iters/gridpt Error, Sum: rho 6.378e-08, 2.433e-05 | tau nan, -nan | Sx nan, nan | Sy nan, nan | Sz nan, nan

To investigate this problem, I added the following parameters:
Multipole::interpolator_name = "Lagrange polynomial interpolation"
Multipole::interpolator_pars = "order=4"

I also changed the parameter Driver::ghost_size  from 3 to 4, but the same error occurred.

I would like to ask:

  *
What could cause tau, Sx, Sy, and Sz to become NaN in this situation?
  *
Does this indicate a failure of  C2P conversion?
  *
Are there any parameter settings or initial data that I should check first?

Additionally, I have another question. When I use kuibit to extract Psi4, I expected to obtain the full time series (or all available modes) but the returned object contains only one element, for example,
      SimDir.gws[100][(2,2)].y=[-9.79586237e-15-5.27476073e-14j].

Other attributes such as
       SimDir.gws[100][(2,2)].x

also contain only one element. Is this a correct behavior or could it indicate a problem with my .par file?

For reference, I have attached my parameter file.

Thank you very much for your time and any suggestions.

Best regards,

Taiki Makino

Graduate School of Science, Nagoya University

makino.taiki.g6 at s.mail.nagoya-u.ac.jp<mailto:makino.taiki.g6 at s.mail.nagoya-u.ac.jp>

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