Thanks a lot Zach, Roland and Ian for your comments. We are currently compiling the last version of the EinsteinToolkit and we will make some runs with different values of CarpetRegrid2::min_fraction to check if the noise disappears. We will report you the results in a few days.
Best Regards, Toni. El jue., 7 mar. 2019 a las 14:47, Ian Hinder (<[email protected]>) escribió: > > > On 7 Mar 2019, at 07:40, Antoni Ramos Buades <[email protected]> > wrote: > > Hi, > > Roland you are right it is forming and destroying a common box each time > the outburst of noise happens. Do you know how one could get rid of this > noise, or if there are some parameters of Carpet which one could add to > the parameter file to avoid such a behaviour? > > > Hi Antoni, > > There is this parameter in CarpetRegrid2: > > CCTK_REAL min_fraction "Minimum fraction of required refined points that > need to be present in a refined region" STEERABLE=always > { > 0:* :: "" > } 0.9 > > When two boxes overlap, CarpetRegrid2 has to make a decision about whether > to use the union of the two boxes, or to replace the two boxes with a > single enclosing box. This code is in carpet/CarpetRegrid2/src/ > property.cc in the function combine_regions::test_impl. The decision is > made based on the number of point in the union of the two boxes, vs the > number of points in a single enclosing box. It will leave the regions > separate if > > min_fraction * combined_size > regions_size > > which, with the default of 0.9, means that the number of points in the > single enclosing region is greater than 1.11 times the number of points in > the original regions. The logic for this is that having lots of regions > means lots of faces, edges and corners, and more communication and > prolongation, which can affect performance and might also be undesirable > due to creating numerical error features such as reflections. On the other > hand, the single enclosing region will contain more points, and hence will > be more expensive to evolve. min_fraction allows you to decide how many > extra points you are willing to evolve, for the sake of having only a > single box. If there would be more than 1/min_fraction times the number of > points by combining, the code does not combine. > > If you set > > CarpetRegrid2::min_fraction = 1 > > > then Carpet will never create a single enclosing box, but will always give > you a box based on the union of the points in the two boxes. > > Ninja'd by Roland. Sigh... > > -- > Ian Hinder > Research Software Engineer > University of Manchester, UK > >
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