Users December 2025

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7 participants
10 discussions

Loss of convergence with subcycling in time
by Miguel Zilhão 17 Feb '26

17 Feb '26

hi all, we've recently added the option to compute the Gauss constraint in the ProcaEvolve thorn (https://bitbucket.org/canuda/proca/src/experimental_miguel/ProcaEvolve/) and we were surprised to see that, even for very small evolutions of a simple (unperturbed) charged black hole, this constraint violation does not converge. of course everything is converging just fine at t=0, but once the evolution starts, convergence is lost really quickly. after experimenting with different things, i think i've narrowed the issue down to the subcycling in time. i've attached some plots as well as the corresponding parameter files. these plots are not convergence tests, it's just what i'm observing with and without subcycling in time (everything else is the same as you can see from the parfiles). these are evolutions for a single charged BH, with Q=0.2. in one of the parfiles (LeanBSSN_RN_Q0.2_nosubcycl_hf40_202509.par) all timelevels update at the same rate with Carpet::time_refinement_factors = "[1, 1, 1, 1, 1, 1, 1]" for the other parfile (LeanBSSN_RN_Q0.2_hf40_202509.par), all timelevels update at the same rate *except* the two inner ones. for the "base" grid functions, i see no noticeable difference insofar as i've checked, but for the Gauss constraint violation the results are very different as you can see from the plots attached: - in the gc_x_RN_nosubcycl.pdf plot, everything looks fine - in the gc_x_RN_subcycl.pdf case, notice how a lot of noise propagates from the two inner refinements levels -- the ones that updated more frequently than the rest. the problem is that this noise is not contained in the buffer region (if it was, we'd be fine), but propagates out, contaminates the rest of the grid, and totally ruins any convergence study. actually a similar thing also happens for the hamiltonian constraint -- plots also attached (hc_x_RN_nosubcycl.pdf, hc_x_RN_subcycl.pdf) -- but in this case the effect is smaller and it doesn't spoil convergence studies. so i was wondering whether this is at all expected and/or if there are some parameters or setting that we may have overlooked? thanks, Miguel

4 7

Safe check of variable Coordinates::volume_form_state
by Jordan Nicoules 20 Jan '26

20 Jan '26

Dear all, I'm trying to extend our analysis thorn to tackle multipatch grids built with Llama. I want to use Coordinates::volume_form in the computation of volume integrals, by setting the corresponding parameter Coordinates::store_volume_form = yes. Our standard use case relies on Coordinates::coordinate_system = "Thornburg04", for which it works like a charm. However, except for this system and the analogous Thornburg13 (I have not tested it so far), it seems the variable Coordinates::volume_form_state is not modified nor initialized, whatever the value of the parameter Coordinates::store_volume_form. That makes the parameter insufficient by itself to perform checks. Moreover, since the flag is not initialized, we also can't simply check its value, which can be polluted. I have tried to use Carpet::poison_new_timelevels = yes and CarpetLib::poison_new_memory = yes, but it didn't seem to solve the issue. Hence, I would like to ask if there's another way to check for uninitialized values, a safe way to use the variables I mentioned in a general case, or any information/subtlety I may have missed? Ultimately, I can directly check Coordinates::coordinate_system, and output a warning/error if it's not of the types mentioned above. That feels a bit unsatisfactory, although I may default to it. Thank you very much for any help or insight you can provide! Best, Jordan Nicoules

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Meeting minutes for 2025-12-18
by Steven Brandt 18 Dec '25

18 Dec '25

Present: Steve, Peter, Beyhan, Zach, Roland, Maxwell Rizzo, Deborah, Lucas Chair: Deborah To be included in the next release: - LSU: Cottonmouth - UIUC: CandudaX - Idaho: Bhahaha - Maxwell Rizzo: volume integral thorns for CarpetX (Zach will review) Names of previous releases are here: https://docs.einsteintoolkit.org/et-docs/Release_Details Time to start pondering new ones Testsuite runners: - Steve: LSU machines, some standard linuxes - Maxwell Rizzo: Anvil - Deborah: Stampede 3 - XSEDE machines? - New machines? Discussions on mailing list: - Miguel Zilhao asks about loss of convergence with Carpet We should follow up to find more details Evolved with Proca Tickets: - Remove TAGS='...' from interface.ccl (Roland) - Interpolator CACHES (Roland and Erik) - NewCGH field cctk_patch_is_cartesian (Roland) - Generic names of headers in CarpetX is problematic - Issue 2888: race condition, need a replicatable error

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Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 17 Dec '25

17 Dec '25

Hello, Please consider joining the weekly Einstein Toolkit phone call at 9:00 am US central time on Thursdays. For details on how to connect and what agenda items are to be discussed, use the link below. https://docs.einsteintoolkit.org/et-docs/Main_Page#Weekly_Users_Call --The Maintainers

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Not found response
by Gal Shua Yehoshua-Abramskey 17 Dec '25

17 Dec '25

Hello, While trying to reach the tutorial server on https://etk.cct.lsu.edu/ I received a Not found page, could you help revive it? Thanks, Gal.

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meeting minutes for 2025-12-11
by Roland Haas 11 Dec '25

11 Dec '25

Present: Leo, Roland, Peter, Steve, Zach, Beyhan, Deborah, Johnny, Keith, Lucas, Nikolai Chair: Leo Minutes: Roland ET EU meeting 2025 discussion ============================= * Beyhan reported on numbers of attending participants * recordings and slides are available at https://sites.google.com/view/eetk25 * minutes of discussion will be added soon * next US meeting will be at UIUC * next EU meeting is TBD ET 2026 release =============== * Steve is chair * Roland is future chair * Beyhan agreed to help * Deborah agrees to help with gallery runs * Lucas volunteers to run gallery examples * Johnny agrees to run gallery * Roland mentions that BHNS gallery example should be in the making * Roland suggests that having a BNS example that is not using LORENE and GRHydro would be nice * Leo and Peter suggest that using FUKA as ID reader is not too expensive * Beyhan suggests that SGRID would offer more options for initial data ** Steve and Peter suggest reaching out to Wolfgang Tichy for an introduction Questions on the mailing list ============================= Older messages since from before US Thanksgiving * "Loss of convergence with subcycling in time" https://lists.einsteintoolkit.org/pipermail/users/2025-November/009815.html Steve is concerned about lack of convergence, Erik pointed out that full Christmas tree scheme must be used that does not use any interpolation in time at all * "Safe check of variable Coordinates::volume_form_state" https://lists.einsteintoolkit.org/pipermail/users/2025-November/009821.html Suggest to create a ticket since this seems to be a bug. Storage itself can always be checked via CCTK_VarDataPtr Tickets on list =============== * "BHNS with Elliptica: Assertion `all(offset == other.offset)' failed" https://bitbucket.org/einsteintoolkit/tickets/issues/2899/ . No progress, Roland now has access to MN5. * "CarpetX: interpolation with z-reflection symmetry only works for Psi4", https://bitbucket.org/einsteintoolkit/tickets/issues/2902 . Roland says this would be nice to have for upcoming release. * "NoiseX: Improve noise generation in CarpetX", https://bitbucket.org/einsteintoolkit/tickets/issues/2855 . Moved to top since Roland added comment based on Erik's observation that vertex centered grid double cover the last grid point * "CarpetX: Interpolator caches" https://bitbucket.org/einsteintoolkit/tickets/issues/2898 . Lucas is re-implementing so as to not use a cache but provide finer grained control to caller over stages (setup and interpolate) * "GetComponents: add support to set push_url in git" https://bitbucket.org/einsteintoolkit/tickets/issues/2896 Steve will review * "PUGH tries to free memory not allocated by malloc", https://bitbucket.org/einsteintoolkit/tickets/issues/2764 . No progress. * "Improve McLachlan accuracy", https://bitbucket.org/einsteintoolkit/tickets/issues/963 . Peter and Zach are still working on this. Any other business ================== * Roland mentioned prior efforts of transitioning Cactus codes to github and need to reach out to current owner of cactuscode github user name * Lucas brought up the issue that Perl is becoming less and less familiar to developers of Cactus code. Suggests to try and see if a transition to Python (3) maybe using a LLM to help it possible. Need to ensure that a common version of Python 3 is installed on all clusters. We will meet once more this year next week (Dec 18th), then skip Christmas day (25th) and New Year's day (1st). Next chair: Deborah Next minutes: Nikolai 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://pgp.mit.edu .

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Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 10 Dec '25

10 Dec '25

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Changing Timestep Size at Recovery?
by Allen Wen (RIT Student) 10 Dec '25

10 Dec '25

Hello, Is there a clean way to change the timestep size in a Carpet simulation on recovery (eg. effectively making Time::dtfac steerable)? I am running into numerical instabilities late in a simulation and was wondering if reducing the dtfac would help. While I am using multiple refinement levels with subcycling, I can ensure all levels are aligned in time at this checkpoint if it helps. Thanks, Allen Wen

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Meeting Minutes 2025-11-20
by Keith Dow 01 Dec '25

01 Dec '25

Present: Roland Haas (chair), Keith Dow (minutes), Miguel Zilhão, Leo Werneck, Bill Gabella, Deborah Ferguson, Zach Etienne, Lucas TS, Beyhan Updates: There is no meeting next week (American Thanksgiving) or the week after because of the European ETK meeting. Invited speakers to the European ETK need to get their abstracts in to Beyhan. Q. Is there an easy way to switch the BH example to CarpetX? A. No. Questions: Miguel Zilhão has an ongoing issue with convergence. The issue appears to be a time step issue with sub cycling. Tickets: #2888 Steve and Roland are working on resolving a race condition issue. #2903 and #2901 There is a bug in the detect script. A fix is being looked at. #2892 GPU issue. Issue not resolved. #2900 This is an issue with a Lonestar configuration file. Maybe a Lonestar 6 config will fix it. #2898 Lucas is to implement a solution. #2897 A solution needs to be tested. #2896 A few lines of Perl code would solve this issue. No one assigned.

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No Einstein Toolkit call this week
by Roland Haas 01 Dec '25

01 Dec '25

Hello all, Due to the ongoing EU ET summer school and workshop (https://sites.google.com/view/eetk25) there will be no regular Einstein Toolkit call this week on Dec 4th 2025. 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://pgp.mit.edu .

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