The issue with the time step size (see probably <https://arxiv.org/abs/1003.0859>) occurs on the coarsest levels only. If the error occurs near the puncture on the fine grid, then this is not the problem.
Some of the gauge parameters have a dimension (e.g. 1/length). The "standard" settings are optimized for M=1. If your black hole mass is very different, then you might need to change them. If you have a total mass of M=4, then the gauge might try to act four times faster than usual, leading to an instability. The cure would then be increased resolution, or changing the respective parameters. -erik On Wed, Nov 27, 2019 at 8:52 AM Wolfgang Kastaun <[email protected]> wrote: > > Hi Bruno, > > Not sure if related, but I vaguely recall that the gamma-driver shift > gauge condition can become unstable if the timestep exceeds a critical > value related to the damping constant eta in the driver. This might > happen with 9 levels if the timestep is also increasing by a factor 2 > with each level. The solution I remember was to use the same timestep > for the few coarsest levels. Do you know if the first occurrence of NANs > in the shift happens on the coarsest level? > > Cheers, > Wolfgang. > > On 11/27/19 12:36 PM, Bruno Giacomazzo wrote: > > Dear All, > > a student of mine (Giulia Crotti) is having issues running a NS-BH > > simulation with GRHydro and McLachlan (parfile attached). The problem we > > are having is with the metric evolution (see attached image for the > > lapse produced just before the crash) and I don't think I ever saw such > > a problem. Does any of you have any suggestio? > > > > Approximately around 2000 iterations the simulation crashes with the > > following error: > > > > ERROR from host r168c12s01.marconi.cineca.it > > <http://r168c12s01.marconi.cineca.it> process 0 > > > > while executing schedule bin CCTK_EVOL, routine > > PunctureTracker::PunctureTracker_Track > > > > in thorn PunctureTracker, file > > /marconi/home/userexternal/gcrotti0/EinsteinToolkit/ET_2018_09/Cactus/arrangements/EinsteinAnalysis/PunctureTracker/src/puncture_tracker.cc:204: > > > > -> Shift at puncture #0 is (-nan,-nan,-nan). This likely indicates an > > error in the simulation. > > > > > > Something is wrong with the metric; indeed the lapse function gets > > larger than 1. We have 9 refinement levels on the black hole, with a > > resolution of 0.045 on the finest grid. The initial data have been > > computed as to get a mass ratio = 3; so the black hole mass is ~4 solar > > masses. The black hole is non-spinning. > > > > > > Thanks, > > > > Bruno > > > > > > -- > > > > Prof. Bruno Giacomazzo > > Department of Physics > > University of Milano-Bicocca > > Piazza della Scienza 3 > > 20126 Milano > > Italy > > > > email: [email protected] <mailto:[email protected]> > > phone: (+39) 02 6448 2321 > > web: http://www.brunogiacomazzo.org <http://www.brunogiacomazzo.org/> > > > > ---------------------------------------------------------------------- > > There are only 10 types of people in the world: > > Those who understand binary, and those who don't > > ---------------------------------------------------------------------- > > > > > > _______________________________________________ > > Users mailing list > > [email protected] > > http://lists.einsteintoolkit.org/mailman/listinfo/users > > > _______________________________________________ > Users mailing list > [email protected] > http://lists.einsteintoolkit.org/mailman/listinfo/users -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/ _______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
