Users September 2026

users@lists.einsteintoolkit.org

7 participants
21 discussions

Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 30 Sep '26

30 Sep '26

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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Agenda for Thursday's Meeting
by users＠einsteintoolkit.org 28 Sep '26

28 Sep '26

Please update the Wiki with agenda items for Thursday's meeting. Thanks! https://docs.einsteintoolkit.org/et-docs/meeting_agenda --The Maintainers

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Geodesic: status on the multi-process (MPI) + AMR path (this week's users call)
by Yuhua Li 24 Sep '26

24 Sep '26

Dear all, Following my presentation of Geodesic at the previous weekly users call, I would like to give a brief status on the one item I flagged as an open limitation: exercising the multi-process (MPI) configuration on a Carpet AMR evolution. The single-process + AMR runs already reproduce the unigrid reference orbits with the three samplers, with no lost particles and no NaNs. Since then I have been working on the MPI path, but the work is still under test: current MPI + AMR runs still show particle loss with non-finite metric samples, and I am debugging the cause. I do not yet have a clean, reproducible result, so I have no conclusion to report this week. In short: no new deliverable on the MPI + AMR path this week -- it is still under verification. I will report a concrete result as soon as the verification passes. I remain available to discuss, and as before I am most comfortable continuing in writing. Any questions are welcome. Best regards, Yuhua Li

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meeting minutes for 2026-09-24
by rhaas＠mail.ubc.ca 24 Sep '26

24 Sep '26

Present: Roland, Peter, Steve, Beyhan, Jordan, Maxwell, Nikolai, Zach Transition wiki to GitHub ------------------------- * Steve presented current state of attempt to transition MediaWiki wiki to GitHub wiki * please take a look at https://github.com/EinsteinToolkit/wiki/wiki * ticket at https://github.com/EinsteinToolkit/tickets/issues/2256 * access is controlled via GitHub org for ET MacLachlan updates ------------------ * Peter is still trying to run on LSU machines, will contact Steve to test out simfactory settings Mailing list questions ---------------------- * Steve will respond to http://lists.einsteintoolkit.org/pipermail/users/2026-September/010041.html ** Zach provided the inclusion criteria: https://www.einsteintoolkit.org/contribute.html * we are not clear what to do about http://lists.einsteintoolkit.org/pipermail/users/2026-September/010034.html Open tickets ------------ * https://github.com/EinsteinToolkit/tickets/issues/2956 has a branch and Erik has a (separate) pull request https://bitbucket.org/cactuscode/cactus/pull-requests/180 and https://bitbucket.org/cactuscode/cactustest/pull-requests/7 * https://github.com/EinsteinToolkit/tickets/issues/2974 Peter will take a look at this summation-by-parts contribution * https://github.com/EinsteinToolkit/tickets/issues/719 concerns updating mailman, mailman 2 is now old enough to be no longer supported and we are in the process of upgrading to mailman 3 * https://github.com/EinsteinToolkit/tickets/issues/2960 "CarpetRegrid2: failure to regrid on relative radius change - possible underlying race condition" has a reproducer and should be addressed * https://github.com/EinsteinToolkit/tickets/issues/2965 "GetComponents option to obtain new branch", is looking for a reviewer. Steve will try * https://github.com/EinsteinToolkit/tickets/issues/2973 "Add support for Multi-step Runge-Kutta methods in CarpetX/ODESolvers" Steve is pushing to have this included * https://github.com/EinsteinToolkit/tickets/issues/2961 "util_ExpressionEvaluate fails with custom evaluator" Steve has PR that he will link * https://github.com/EinsteinToolkit/tickets/issues/2909 "Remove TAGS from interface.ccl" has comments 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 23 Sep '26

23 Sep '26

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Agenda for Thursday's Meeting
by users＠einsteintoolkit.org 21 Sep '26

21 Sep '26

Please update the Wiki with agenda items for Thursday's meeting. Thanks! https://docs.einsteintoolkit.org/et-docs/meeting_agenda --The Maintainers

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Fwd: Applications Open for Postdoctoral Research Positions at Perimeter Institute for Theoretical Physics
by Roland Haas 21 Sep '26

21 Sep '26

-------- Original Message -------- SUBJECT: Applications Open for Postdoctoral Research Positions DATE: 2026-09-21 10:05 FROM: William East <academic(a)perimeterinstitute.ca> TO: rhaas(a)mail.ubc.ca REPLY-TO: peopleandculture(a)perimeterinstitute.ca [CAUTION: Non-UBC Email] Perimeter Institute for Theoretical Physics is inviting applications for Postdoctoral Research positions. ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ ͏ Dear Valued Colleague, Perimeter Institute for Theoretical Physics is inviting applications for the Postdoctoral Research Program [1]. For more information, please visit the job posting [2]. We hope you will share the news by: * Forwarding this information directly to prospective candidates who may be interested in this opportunity * Downloading, printing, and hanging the poster [3] * Sharing LinkedIn [4] and Facebook [5] posts with your social networks Perimeter Institute offers a dynamic, multi-disciplinary environment with maximum research freedom and opportunity to collaborate. We welcome all candidates to apply by November 6, 2026 but applications will be considered until all positions are filled. Thank you in advance for forwarding and sharing this information. Sincerely, William East Committee Chair Links: ------ [1] https://landing.perimeterinstitute.ca/e3t/Ctc/2I+113/cjL-604/VWy7sc2gdh7VW3… 3bYncS8TB7jMW2Gfc0n3xXmdJW6DmBg26P8JB6W1yv_6f3qkVnyW1qzrnm55SSmFW8-tkVb641HFGW8dygWn77VLqxV72Zq66cPmJyV8ZtLS29yzH6W4bql0y5DDBhTW5MTHRx4g4_6JW4RPZPd8Ny8sRW2KtWMm5NmTQtMpZHcRfr_rwW5qtqf44k0zNBW41HKz544ypzNW2gjKqg59rbJ9W5Jl52y5n94VjW8bhWdV8Zbkv5W4rCMCB4Kk-_dVPr-pc5CqZlXW3tfQkn51tb8zdSwHk204 [2] https://landing.perimeterinstitute.ca/e3t/Ctc/2I+113/cjL-604/VWy7sc2gdh7VW3… [3] https://landing.perimeterinstitute.ca/e3t/Ctc/2I+113/cjL-604/VWy7sc2gdh7VW3… [4] https://landing.perimeterinstitute.ca/e3t/Ctc/2I+113/cjL-604/VWy7sc2gdh7VW3… [5] https://landing.perimeterinstitute.ca/e3t/Ctc/2I+113/cjL-604/VWy7sc2gdh7VW3…

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Meeting minutes for 09/17/26
by Deborah Ferguson 17 Sep '26

17 Sep '26

Chair: Roland Minute taker: Deborah Attendees: Deborah, Roland, Jordan, Peter, Maxwell, Zach, Nikolai, Ameen, Yuhua, Lucas Accumulated updates after the release - AMRex merged in - Mchlachlan updates - peter has been able to compile, but having some run issues Status of issues on github - the new tickets based on github are now up - yet to update the website - some tickets ready to be added to it - tickets are now authored by a bitbucket-to-github transition bot - mentions resolve as a hash instead of a username - you may have an email inviting you to join the ETK organization - ping tickets if need be to adjust update times - thank you Zach for all his work - Jordan suggesting sending an email to the mailing list about this (will be done soon) Potentially hosting the wiki on github - reduce LSU reliance - previously considering doing this on bitbucket (old issue: https://github.com/EinsteinToolkit/tickets/issues/2256) - github wiki seems better so may be worth it - things to consider - we want tables - media wiki does have more capability, anything we need? Unanswered questions - New thorn proposal - will be discussed over email - Independent researcher wanting to use ETK to test a theory - possibly an AI? Issues: - GetComponents suggestion / pull request from Jordan - adds options to switch branch - Roland isn’t sure whether this will fully make it updatedable - would need to also adjust symbolic links - likely would get you 80% of the way there - Cottonmouth - is already included, not sure why the ticket is still open - Lucas will look into - FUKA ticket from Samuel Tootle - Peter will take a look - will see if Samuel can join a call at some point - Regression in TwoPuncturesX - Zach thinks this has been resolved - wait to discuss next week - BHNS gallery example - needs to be closed - BHaHAHA - needs to be closed - also close its duplicate - CapyrX has been postponed - CarpetRegrid2 bug - Jordan provided a reproducer with a minimal example - Jordan will ping it to bring it to the top AOB - Zach tells us to expect a few new thorns from his side for the next release - Baikal update coming soon to be much faster ----------------------------------------- Deborah Ferguson Assistant Professor The University of Rhode Island

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Geodesic: a test-particle geodesic thorn (AMR-verified) - for today's weekly users call
by Yuhua Li 16 Sep '26

16 Sep '26

Dear all, At today's weekly users call I would like to briefly present Geodesic, a new thorn that integrates test-particle geodesics in Kerr--Schild Cartesian coordinates, and ask for feedback before submitting it to the Einstein Toolkit. Features - Two metric modes: an exact analytic Kerr--Schild metric (grid-independent, symbolically verified to be a vacuum solution at machine precision), and a grid mode that samples the ADMBase fields with three interchangeable samplers selected by one parameter: local27 (default, 27-point local Lagrange fit), aei (fourth-order pointwise, via AEILocalInterp), and carpet (second-order pointwise quadratic Lagrange). - Adaptive RKF45 integration with per-step renormalization of the four-velocity; d_t g recovered from the three most recent ADMBase time levels (stationary metrics are auto-detected). - AMR-ready: each sampler reads the refinement level that contains the particle, so geodesics can be integrated inside a Carpet AMR evolution (with 4:1 subcycling) without any change to the integrator. - OpenMP-parallel particle loop: scales to 10^4 particles (9.2x speedup, 10.4% efficiency on 88 threads); embedded in a full GRHydro evolution, tracking 10^4 particles costs only ~3.1% of the wall time. Verification - E, L_z and the norm conserved to ~1e-9 over T = 1000 M on three distinct bound orbits (circular, tilted, eccentric). - Grid convergence of the default sampler with a measured local order of 3.7 (formal order three) against an independent reference. - Five-way comparison of the exact metric and the three samplers on a precessing orbit of 200 particles close to the plunge boundary. - New: on a 3-level Carpet AMR mesh (50^3 base, dx=1; refinement boxes of half-width 16/8, factor 2), all three samplers reproduce the unigrid reference orbit of conv100 over ~1.05 orbital periods (t = 0..150.1): radial deviations 0.4% (local27), 0.5% (aei), 2.3% (carpet, consistent with its second formal order), with no lost particles and no NaNs. Code and configurations - Repository (GPLv2+): https://github.com/wylyhzh/Geodesic - Includes a 7-test testsuite, ThornGuide documentation, and the parameter files used for the results above (including the three AMR-vs-unigrid comparison setups). - A paper describing the implementation and the verification suite is in preparation. Known limitation - The multi-process (MPI) particle layout is implemented (DISTRIB=CONSTANT, rank-0 integration with state synchronization) but has not yet been exercised with the current rework; single-process OpenMP runs are the tested configuration. The aei sampler in addition needs single-process runs or AEILocalInterp's N_boundary_points_omit when its fourth-order stencil would cross a processor boundary. Any feedback is very welcome - in particular on whether the thorn should be proposed as EinsteinAnalysis/Geodesic. Best regards, Yuhua Li

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Einstein Toolkit Meeting Reminder
by users＠einsteintoolkit.org 16 Sep '26

16 Sep '26

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