[Users] [Commits] [svn:einsteintoolkit] Paper_EinsteinToolkit_2010/examples/bbh/ (Rev. 85)

Bruno C. Mundim bcmsma at astro.rit.edu
Wed May 11 12:30:13 CDT 2011

Thanks, Erik! On a related note: I checked if CarpetMask was setting 
weight[ind]=0 inside the horizons and it seems to do so correctly.
However CarpetReduce::weight still do not reflect that. Its output
still doesn't have the horizons masked out.


Erik Schnetter wrote:
> On Wed, May 11, 2011 at 12:53 PM, Bruno C. Mundim <bcmsma at astro.rit.edu> wrote:
>> Hi Roland:
>> Roland Haas wrote:
>>> Hello Bruno,
>>>>  a) Its evolution is stopped with Nans around 8.6M. Nans appear to come
>>>>  from the BSSN fields, but still needs further investigation.
>>> Hmm I could evolve the qc0 example in McLachlan. Maybe there are
>>> differences in the parameter file that make the error "obvious".
>> A few obvious changes that I can think of:
>> 1) I reduced the number of spherical surfaces from 5 to 3. Now the
>> puncture tracker uses surfaces 0 and 1, AHFinderDirect track those
>> surfaces and load AH related info there. QLM, CarpetTracker and
>> CarpetMask uses those 2 surfaces then. I will go back to 5 surfaces
>> as it was set before. Maybe I am missing some subtle scheduling order
>> here. I don't know.
>> 2) I added a few general parameters I am used to use to CarpetInterp,
>> CarpetLib and CarpetRegrid2.
>> 3) From a discussion I had with Peter on the ET workshop, I decided
>> to change the AHFinderDirect interpolator to Hermite.
>> So I will switch back to what it was and avoid to do so many changes
>> at once! :) However I find strange that these changes could be the
>> cause of what I am seeing.
>>>>  c) When CarpetReduce::weight is output, its values seem strange to me.
>>>>  Most of the domain has 1/2 set. A few points close to the boundary 1/4
>>>>  and the boundaries 0 (physical and ghost). No mask out values inside
>>>>  AH is shown, ie they still are set to 1/2. These values seem to make
>>>>  more sense to AMR restriction operations.
>>> Are you maybe looking at the z=0 plane? That plane has a weight of 1/2
>>> since only half of the volume of each cell is used when eg. computing
>>> the simulation volume. I have never used CarpetMask myself (but have
>>> written a similar thorn of my own... would have paid to look into Carpet
>>> first I guess :-) )
>> Yes I was looking at the z=0 plane and had refection symmetry set up!
>> Thanks for pointing this out. If we go out of the plane then the
>> weight=1.0 values show up. A more careful look into the data, I noticed
>> the zeros are set in the buffer zones indeed with the exception of the
>> third point (ghostzone=3) in the domain (from the AMR boundary) that has
>> its value set to 1/4. Do you know why?
> For some reason that I currently cannot recall, the ghost zones in the
> mask may be set to 1 instead of 0. However, ghost zones are ignored
> anyway by a different mechanism when reducing (by using cctk_bbox and
> cctk_nghostzones).
> The particular values indicate how much of the "control cell"
> surrounding this grid point should be taken into account when
> reducing. If the value is 1/4, then you may be looking at an edge
> point (e.g. and x-y edge in the z=0 plane), where 3/4 of the control
> cell are already covered by the corresponding coarse grid.
> One important test is that the sum of all weights times the grid cell
> volume equals the total volume of the simulation domain. If you look
> into the simulation log output and search for "volume" there, you
> should find a corresponding statement.
> -erik

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