[ET Trac] [Einstein Toolkit] #889: GRHydro atmosphere bug

[Einstein Toolkit]

#889: GRHydro atmosphere bug
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 Reporter:  reisswig  |        Type:  defect               
   Status:  new       |    Priority:  critical             
Milestone:            |   Component:  EinsteinToolkit thorn
  Version:            |    Keywords:  GRHydro, atmosphere  
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 I have fixed a bug in GRHydro's atmosphere handling after reconstruction.
 After reconstruction, the reconstructed plus and minus face values are
 tested for whether they drop below atmosphere level and are then reset.
 In particular, this means that plus and minus face values for cell i don't
 generally coincide with the minus/plus face values of the corresponding
 cells i-1 and i+1.
 If the reconstruction previously found that the Riemann problem was
 trivial between, say rhominus(i+1) and rhoplus(i), when changing
 rhoplus(i), it is not anymore!
 However, the mask "trivial_rp" testing for a trivial Riemann problem is
 not changed!
 This leads to inconsistent behavior at the boundary of the atmosphere.

 The symptom was a drift in the center of mass of a static and perfectly
 symmetric TOV star.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/889>
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