Users March 2012

users@lists.einsteintoolkit.org

23 participants
48 discussions

Einstein Toolkit Meeting Reminder
by Frank Loeffler 14 May '15

14 May '15

Hi Please consider joining the weekly Einstein Toolkit phone call at 10 am US central time on Mondays. As usual, you can find instructions how to join on the following web site: http://einsteintoolkit.org/community/support/ I short: the number is (+1) 225-578-4942 or (+1) 866-573-0359 and the conference id is 118682#. My agenda contains: - Fall workshop - PLEASE let us know if you come [1]! - Hotel booking - Release planning - release date: Mon Oct 24 2011 - freeze date: Mon Sep 26 - the day of the call! - branch name: ET_2011_10 - List of release-concerning bugs [2] - ET paper: proposed "freeze" by Oct 3rd (Mon after this call) As always: feel free to add to this list. Frank Loeffler [1] https://docs.einsteintoolkit.org/et-docs/ET_Workshop_Fall_2011#Fall_Einstei… [2] https://trac.einsteintoolkit.org/query?status=!closed&milestone=ET_2011_11&…

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Simulation domain volume and reduction weight sum differ
by Jakob Hansen 25 Sep '12

25 Sep '12

Hi, Using mercurial, I get this warning during simulations : INFO (CarpetReduce): Simulation domain volume: 170368000 INFO (CarpetReduce): Reduction weight sum: 170367999.880642 WARNING level 1 in thorn CarpetReduce processor 0 host tachyon2974 (line 120 of /home01/r632kgw/jakob/CactusP/arrangements/Carpet/CarpetReduce/src/mask_test.c): -> Simulation domain volume and reduction weight sum differ Simulations seem to run okay though. What is causing this warning and is it serious or can I just ignore it? Cheers, Jakob

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support_old_CalcTmunu_mechanism
by Frank Loeffler 23 Sep '12

23 Sep '12

Hi, Are there objections to change the default of TmunuBase::support_old_CalcTmunu_mechanism from "yes" to "no"? Frank

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Propose thorns for inclusion in the EinsteinToolkit
by Barry Wardell 26 Apr '12

26 Apr '12

Hi, Recently Ian Hinder and I have created an arrangement of thorns called EinsteinExact which provide some exact solutions for use in Cactus. The scope of these thorns is similar to that of the Exact thorn but with some notable improvements: * The extrinsic curvature is computed symbolically rather than using finite differencing so it should be accurate to within roundoff. This means that EinsteinExact is more exact than Exact. * The solutions used in EinsteinExact come from a database of metrics which have been correctness-tested, e.g., by checking symbolically that they are a solution of the Einstein equation. * EinsteinExact is written in Mathematica and uses Kranc, so the raw source is very small (~250 lines) and easy to understand. * Adding a spacetime is as simple as typing the components of the metric into Mathematica. So far, the spacetimes included are Minkowski, Kerr-Schild, gauge wave and shifted gauge wave, but the list can easily be extended in the future. There is also support for arbitrary rotations, using the same conventions as the Exact thorn uses. We have not yet included the other transformations supported by Exact, but they shouldn't be difficult to add. We have checked that for these spacetimes the Exact solutions converge to the EinsteinExact solutions at the correct finite differencing order used by Exact. We would like to propose the EinsteinExact arrangement for inclusion in the EinsteinToolkit. If you would like to try it out, you can get it using: git clone --recursive git://github.com/barrywardell/EinsteinExact Any comments or suggestions are welcome. Regards, Barry

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Meeting Minutes
by Roland Haas 16 Apr '12

16 Apr '12

Present were: Frank, Roland, Peter, Tanja, Josh ET workshop: * Cactus virtual machines should be available for download today, they should include all required software, incl. visualization tools. * please test them in particular if you are handling a hands on session * please try and submit your slides before the APS meeting, using the templates provided to ensure a uniform slide layout * the talks should be aimed at beginning graduate students * the hands on analysis example will be a star tracker as described in the schedule * we currently have 2 confirmed invited speakers and are working on the third. The next phone call will be three (3) weeks from now on April 16th and we will discuss the then upcoming ET release, which is due in May. Yours, Roland

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Illinois Contribution to ET: Staggered Prolongation/Restriction
by Zach Etienne 06 Apr '12

06 Apr '12

Dear ET folks, Our branch of Carpet, which includes the prolongation/restriction operators we developed for staggered gridfunctions, has been made publicly available. You can download it here: http://webusers.physics.illinois.edu/~vpaschal/UIUC_CARPET/ The license to our modifications and contributions is GPL, chosen to maximize compatibility with the rest of the Carpet code licensing. Though we do not intend to merge these changes into the Carpet mainline, you are more than welcome to do so. Sincerely, Zachariah Etienne Yuk Tung Liu Vasilis Paschalidis Stuart L. Shapiro

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Can't evolve Minkowski with RK4 integrator?
by Erik Schnetter 03 Apr '12

03 Apr '12

I've just encountered a strange problem: I can't evolve Minkowski with MoL's RK4 integrator. Small errors in K grow from floating-point round-off, and the simulation quickly goes bad. The error grows slowly (but measurably) in unigrid, but much faster with mesh refinement. For example, with unigrid the lapse grows by about 10^-15 every ten time steps or so; with mesh refinement, the simulation dies after a few ten time steps. However, things are fine with other time integrators, in particular with the generic RK1 and RK4 integrators. I've looked at other things as well, e.g. the CFL factor, the McLachlan implementation, the gauge parameters, dissipation, but could not find anything else that made a difference. Is there something bad about the RK4 integrator? Is it intrinsically unstable, more so than other RK schemes? Or did it break in some of the recent changes? -erik -- Erik Schnetter <schnetter(a)cct.lsu.edu> http://www.perimeterinstitute.ca/personal/eschnetter/

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Re: [Users] cactus simulation build
by Steven R. Brandt 01 Apr '12

01 Apr '12

I agree with Shantenu, you shouldn't have to debug these issues. Just send them to the list where there are a lot of people who can provide answers. In this particular case, I think the error message is badly formatted. The command wants to be issued from inside the Cactus directory. It looks like there used to be a more useful error message in simlib.py in the GetDirSuffix routine, but it was commented out. I'm not sure why. Should we put it back? Cheers, Steve On 03/28/2012 10:49 PM, Sharath Maddineni wrote: > Hello Dr. Steve, > > the cactus simulation build is so flaky/inconsistant > > please see the following commands. This does not make senese at all to > me. I have spending lot of time debugging these kind of issues. Other > than these minor issues running/steps > from there DARE part is done. been encountering these issues all along. > > cactus build exists and when I create some times it does creates and > some times it does not. Please let me know if I am doing anything wrong > /[smaddi2@qb1 einsteintoolkit_build]$ > /work/smaddi2/agent/einsteintoolkit_build/Cactus/simfactory/bin/sim > --parfile=/work/smaddi2/agent/einsteintoolkit_build/Cactus/par/static_tov.par > create --configuration sim static1/ > /Parameter file: > /work/smaddi2/agent/einsteintoolkit_build/Cactus/par/static_tov.par/ > /Skeleton Created/ > /Job directory: "/work/smaddi2/simulations/static1"/ > /Error: Given sourcebasedir > '/work/smaddi2/agent/einsteintoolkit_build' does not contain a Cactus > directory/ > /Aborting Simfactory./ > /[smaddi2@qb1 einsteintoolkit_build]$ ls/ > /Cactuscactus_installer.py einsteintoolkit.th > <http://einsteintoolkit.th> GetComponentsGetComponents.1 > GetComponents.2 GetComponents.3/ > /[smaddi2@qb1 einsteintoolkit_build]$ pwd/ > //work/smaddi2/agent/einsteintoolkit_build/ > /[smaddi2@qb1 einsteintoolkit_build]$ ls Cactus/exe// > /cactus_sim sim/ > > please let me know if I am doing anything wrong. > > Sharath

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cactus performance
by Jose Fiestas Iquira 29 Mar '12

29 Mar '12

Hello, Is there documentation about performance of Cactus ETK in large machines. I have some questions regarding best performance according to initial conditions, calculation time required, etc. If there are performance plots like Flops vs. Number of nodes would help me as well. Other main question I have is if Cactus scales in large machines. I am using McLachlan, but any other application would give me an idea of what I should expect for my runs in big machines. Thanks, Jose

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ETK VM
by Dennis Castleberry 29 Mar '12

29 Mar '12

Dear Frank, and group, The current version of the Einstein Toolkit VM (along with instructions and bug notes) is located at <http://cct.lsu.edu/~dcastl2>. It's LZMA-compressed (my pipelines to the file server are unfortunately short-lived). Regards, Dennis Castleberry dcastl2(a)tigers.lsu.edu

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Users March 2012