[Users] weird behavior with some ET simulations

[Antoni Ramos Buades]

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 (<ian.hinder at manchester.ac.uk>)
escribió:

>
>
> On 7 Mar 2019, at 07:40, Antoni Ramos Buades <antoniramosbuades at gmail.com>
> 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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.einsteintoolkit.org/pipermail/users/attachments/20190307/a8d1ddfc/attachment.html