[Users] Accuracy issue of multipole moment calculations in QuasiLocalMeasures

Hee Il Kim heeilkim at gmail.com
Wed Jun 24 22:07:58 CDT 2015


2015-06-24 16:59 GMT+09:00 Ian Hinder <ian.hinder at aei.mpg.de>:

> On 24 Jun 2015, at 03:15, Hee Il Kim <heeilkim at gmail.com> wrote:
> Hi,
> Recently, I found the multipole moment calculations in QuasiLocalMeasures
> show large errors, e.g. 20% for the second mass moment of my project.
> The error exists even in the test data of the thorn but it's around a few
> percent.
> Note that the "test" directory contains regression tests, which are
> designed to check that the results haven't changed unintentionally when the
> code changes.  They are not meant to test correctness. As such, there is no
> claim of accuracy for their results.  In fact, they should be as small and
> fast as possible, which usually means that they are NOT accurate.  I'm not
> saying that there is no problem; just that the parameter files in the
> "test" directory should not be considered as tests of the correctness of
> the code.
I understand. But the issue is, even though I'm using sufficiently high
resolution for my collapsing star study, the code calculates inaccurately
the higher multipole moments for n >0, where n is the order of the Legendre
polynomial. So it calculates the mass and the spin very accurately.

> Which version of the code are you using?
> It has not changed much recently.
> $ svn log
> https://svn.cct.lsu.edu/repos/numrel/LSUThorns/QuasiLocalMeasures/trunk/
> ------------------------------------------------------------------------
> r57 | eschnett | 2015-04-27 19:05:14 +0200 (Mon, 27 Apr 2015) | 1 line

I'm using the one in ET branch,


Hee Il
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