On Mon, Feb 13, 2017 at 12:09 PM, Roland Haas <[email protected]> wrote: > Present: Eloisa, Frank, Gwyneth, Ian, Yosef, Roland, Steve, > Charalampos, Steve > > CarpetRegrid2: > * regrid_every is the first condition checked, it only ever does > anything if the iteraton is a multiple of it > * movement threshold is an additional condition that prevents grid > movement until the grids have moved a minimum distance > * there is not well known optimal regridding frequency. One > consideration would be to regrid when all timelevels are "in sync" ie > with the same frequency that the coarsest level steps so that there > is no interpolation in time. Another competing consideration is that > the black holes should not have moved too far which gives an upper > limit. A reason to use regrid_every is also if the positions are not > known at every timestep for example if AHFinderDirect is used. With > PunctureTracker is used then the information is known at each time. > * the dominant effect is to regrid frequently enough to track the black > holes moving > * Courant factor is ratio between time step and space step on the > coarsest grid, to compute the courant factor on the finest grid > involves the time refinement factor
To be clear, the CFL factor on finer grids need to take both the spatial and temporal refinement factors into account. > * often one sees that the time refinement factors are set 1,1,2,4,8,... > instead of 1,2,4,8 which is the default. This is due to an > instability in the shift evolution equations. The group in Jena found > this to be important (there is a paper by Bernd Bruegmann et al), > there is a paper by Erik Schnetter that gives reason for this. It is > likely still required for purely Cartesian grids, for Llama > (curvilinear) grids one can get away without doing so One can set the driver conditions in the evolution and gauge equations such that this reduction is not necessary. I don't know whether this has been implemented. > * metric_timelevels is set to 3 for AHFinderDirect setting the same for > lapse an shift does not do harm but there is not directly obvious > reason why one would need it QuasiLocalModes might look at lapse and shift to calculate the full four-metric and its time derivative. -erik > * computing the energy carried of by gravitational waves is done by > computing the WeylScalar on a sphere and then do the integral > yourself. There are a number of analysis packages that help doing so > eg SimulationTools (google find it) by Ian Hinder for Mathematica or > possibly pyCactusET. The list of tools is available here: > https://docs.einsteintoolkit.org/et-docs/Analysis_and_post-processing > * some of GW extraction is shown in the gallery: > http://einsteintoolkit.org/about/gallery/gw150914 and Ian will send > instructions > * if seeing NaNs when running on many nodes or other errors this is a > bug and should at most lead to an error message. static_tov uses a > very small grid and we would suggest using a higher resolution grid. > A gut feeling would say that anything above 27 MPI ranks is > difficult. The issue seems to happen for 40 MPI ranks. > > Website: > * comments from Ian via email > * comments from Roland, who will incorporate them into the website > repo: https://[email protected]/einsteintoolkit/www.git > > MHD workshop: > * https://docs.einsteintoolkit.org/et-docs/2017_MHD_Workshop has the > wiki page > * Roland will write a summary in an email > > ET fails to build right now > * there is an unsupported OMP pragma in MoL, seems like a compiler > specific issue > * Roland suggests to check if all compilers on our "usual" clusters > support "OMP simd" yet > > GetComponents: > * https://trac.einsteintoolkit.org/ticket/1916 contains a > parallelization for GetComponents please give it a try to see if you > can make it break > > 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://keys.gnupg.net. > > _______________________________________________ > 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
