[Users] WENO-Z in GRHydro

Roberto De Pietri roberto.depietri at unipr.it
Fri Jan 17 04:17:11 CST 2020

Dear Bruno:

We did some weno-z test for dynamical bar-mode instability of differentially rotating neutron stars.
It reproduced the results of ppm but we did not perform convergence test. For the moment
We did not test it for BNS systems since the only possible converge test are for the inspiral phase and 
we did not expect any differences there.


> On 17 Jan 2020, at 10:50, Bruno Giacomazzo <bruno.giacomazzo at unimib.it> wrote:
> Roland,
>  thank you very much for the information. 
> My student (Beatrice Giudici, in cc to this email) told me that this is the same WENO-Z that is used by Bernuzzi in his BAM code (https://ui.adsabs.harvard.edu/abs/2016PhRvD..94f4062B/abstract <https://ui.adsabs.harvard.edu/abs/2016PhRvD..94f4062B/abstract>). She is going to do some tests, starting with the Balsara tests and compare it with MP5 and WENO. We will then probably move to oscillating TOV and then BNS (maybe doing some of the tests that Roberto did in his paper with WENO).
> We will keep you posted. I just wanted to check what the status was. I added Roberto in this discussion because of his work with WENO and GRHydro, so I was wondering if he had a look also at WENO-Z.
> Thanks,
> Bruno
> Il giorno gio 16 gen 2020 alle ore 19:30 Haas, Roland <rhaas at illinois.edu <mailto:rhaas at illinois.edu>> ha scritto:
> Hello Bruno, Roberto,
> > I just discovered that GRHydro supports also WENO-Z (a different
> > implementation of the WENO 5th order reconstruction scheme).
> > 
> > I have a master student currently looking at high order schemes and I admit
> > that I thought that GRHydro had only WENO5 implemented
> > (recon_method="weno") since this is the scheme that was mentioned and
> > tested in the GRHydro paper (which instead does not mention WENO-Z which I
> > assume was probably implemented after the paper).
> > 
> > Has the WENO-Z implementation also been tested? Is someone using it?
> It has been years since this was really tested (it was first implemented in December 2012 / January 2013). I believe Christian Reisswig and I have to take blame for implementing any bugs in it. 
> I am no longer quite sure if how much testing was done. I looked through old emails but cannot tell from them whether only WENO (plus changes from Sasha Tchekhovskoy's WHAM paper: https://arxiv.org/abs/0704.2608 <https://arxiv.org/abs/0704.2608>) which were described in the GRHydro MHD paper (Moesta, Mundim et al.) were tested or also the WENO-z implementation.
> Worse, I do not even have a reference from the flavor of WENO-z that was implemented :-(. Could be https://www.sciencedirect.com/science/article/pii/S0021999107005232 <https://www.sciencedirect.com/science/article/pii/S0021999107005232> Borges et al. JCompPhys Volume 227, Issue 6, 1 March 2008, Pages 3191-3211 or something completely different.
> So, while I believe that there was effort to test it, there is no longer a reproducible way to check what was tested and how well it performed.
> Yours,
> Roland
> -- 
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> -- 
> Prof. Bruno Giacomazzo
> Department of Physics
> University of Milano-Bicocca
> Piazza della Scienza 3
> 20126 Milano
> Italy
> email: bruno.giacomazzo at unimib.it <mailto:bruno.giacomazzo at unimib.it>
> phone: (+39) 02 6448 2321
> web: http://www.brunogiacomazzo.org <http://www.brunogiacomazzo.org/>
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