[Users] Documents lack details

[Ian Hinder]

On 26 Feb 2020, at 15:09, 刘昊阳 <liuhaoyang19 at mails.ucas.edu.cn<mailto:liuhaoyang19 at mails.ucas.edu.cn>> wrote:

Dear colleague:

I'm Liu Haoyang, a fresher of EinsteinToolkit from University of Chinese Academy of Science.

I found that some Thorn's documents in Thorn Guide lack detailed description about their variables' function, such as "Carpet" and "ReflectionSymmetry". And it seems that access to https://carpetcode.org/ is restricted.

Is there any other material for such Thorns I can learn about? And how can I have access to the website of Carpet?

Hi,

The best place to look at an overview of the documentation is probably

https://einsteintoolkit.org/documentation/ThornGuide.php

It's true that the Carpet thorn doesn't have any documentation, but the Carpet arrangement does.  This applies to the whole arrangement of Carpet thorns.  You can read it here:

https://einsteintoolkit.org/arrangementguide/Carpet/documentation.html

I'm not sure what happened to carpetcode.org<http://carpetcode.org>.  Erik Schnetter is the original author of Carpet, and his website still has that link (https://www.perimeterinstitute.ca/personal/eschnetter/), so I assume the website has gone down and is unnoticed.  I will ask him in a separate thread.

Yes, the symmetry thorns don't appear to be documented.

Often, you can work out how to use a thorn by looking at the available parameters in params.ccl:

https://bitbucket.org/cactuscode/cactusnumerical/src/master/ReflectionSymmetry/param.ccl

That, at least, is less likely to be out of date than any documentation!

The main idea, if you want to use reflection symmetry, is that you need to set up your domain, e.g. with CoordBase parameters, to contain only the portion you want to simulate.  E.g. if you have a symmetry z -> -z, then you could set zmin = 0.  You then activate ReflectionSymmetry and set ReflectionSymmetry::reflection_z = "yes", ReflectionSymmetry::avoid_origin_z = "no" (the need for the latter is due to an unfortunate default, from what I remember).

--
Ian Hinder
Research Software Engineer
University of Manchester, UK

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