[Users] **large** amplitude changes in WFs from Curie "bbh" parfiles when run in ET_2012_05

[Ian Hinder]

On 7 Nov 2012, at 20:29, "Kelly, Bernard J. (GSFC-660.0)[UNIVERSITY OF MARYLAND BALTIMORE COUNTY]" <bernard.j.kelly at nasa.gov> wrote:

> Hi. This may be related to something Yosef brought up back in July
> ["Differences in results ..." from 26 July], but I'm seeing sizable
> differences in WF amplitudes from Multipole when running the parameter
> files for the ETK paper (Loeffler et al.).
> 
> Specifically, if I take the parameter file
> 
> <Cactus>/par/arXiv:1111.3344/bbh/BBHMedHRes.par
> 
> ... and run it with a Curie (ET_2011_05) executable, my r=30M (2,2) mode
> has a peak magnitude of just above 0.0027. Rerunning the same parameter
> file with *no* changes, using the current release, Lovelace (ET_2012_05),
> the same peak amplitude is just above 0.00257 -- a drop of almost 5%.
> 
> Can anyone tell me what might be going wrong? Is there some kind of change
> in default dissipation that could explain such a large discrepancy?

I don't think so.  McLachlan with its default parameters has always disabled dissipation.  We changed the default of apply_dissipation very recently (i.e. after Lovelace) from "true" to "false" (and announced this on the list), but the dissipation strength has always defaulted to zero. 

Dissipation in that parameter file is provided by the Dissipation thorn, and it uses its default value of epsdiss = 0.2.  

Could this be related to the change in grid structure going from the "git" to the "mercurial" version of Carpet?  Are the grid structures the same? You can output the grid structure to an ASCII file using 

	Carpet::grid_coordinates_filename       = "carpet-grid.asc"

Can you try to narrow down where the differences lie?  For example, you could look at the grid functions themselves, including one of the evolved variables, one of the ADMBase variables, and also Psi4, to see which are actually different.  

-- 
Ian Hinder
http://numrel.aei.mpg.de/people/hinder