[Users] Question about GRHydro + LLAMA

[Roland Haas]

Hello Luciano,

> I'm a relatively new user of the toolkit; I've been mainly using GRHydro
> and I'd like to start using it with LLAMA. I played a bit with the
> multipatch gallery example but I have a few questions:
> 
> 1) Is there a public parfile for a simple TOV or any GRHydro implementation
> using LLAMA (or someone I could ask about it)?
Not sure about fully public, but you are free to use the attached one
that was used in 

https://arxiv.org/abs/1212.1191

though it uses CTGamma rather than McLachlan so will require some
adaptation (or you can use CTGamma which is available in the Llama
repo). It also uses some private thorns (CCCGlobalModes and
Psiclops, WaveExtractL) which you can either remove or use eg
Hydro_Analysis for CCCGlobalModes, and WeylScal and Multipole the way
the GW150914 example does for the waves.

Note: there is nothing really that needs to be done use GRhydro with
Llama, other than setting up the grid, ie it needs no extra parameters
so a Llama parfile could be constructed by merging the gallery bns
example with the gallery GW150914 example (at reduced finite difference
order since order 8 is overkill for a hydro run).

You may also take a look at the Parma group's collection of data and
files (some digging in the website required) starting from here:

https://docs.einsteintoolkit.org/et-docs/Additional_resources

though there is no Llama files I think.

Note that due to the way NSTracker works, the parfile will only work
with equal mass bns systems. For unqual ones the WVUThorns_Analysis has
thorns that can track each bns separately (those thorns won't work with
symmetry enabled but should work with Llama as long as the NS are only
on the Cartesian grid).

> 2) Reading the mailing list I found that there was an issue with the GW
> propagation caused by refinement boundaries (
> https://urldefense.com/v3/__http://lists.einsteintoolkit.org/pipermail/users/2017-March/005411.html__;!!DZ3fjg!q8UZ3uoTcF5BGa-3mdV_BF1Sdv9tQjnP3RipvVq7Mt4xIi_Kc32UI63Ga10flgmj$ ).

I would say those still exist, though there is a possibility that
changes due to 

https://bitbucket.org/einsteintoolkit/tickets/issues/2398/multipole-default-midpoint-integration

have changed behaviour a bit.

> Do you know if this is still an issue?

I would not say "know", but my guess would be "yes, still an issue to
the extend reported by Christian".

> If I get to use it, I'd be happy to contribute in some way, if there's room
> and interest for that.
If you can make the parfile simpler and eg baesd on the bns gallery
example and were to contribute it back, than would be very nice to have.

Yours,
Roland

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