VolumeIntegrals_vacuum inherits directly from ML_BSSN

[Roland Haas]

The analysis thorn `VolumeIntegrals_vacuum` in wvuthorns_diagnostics inherits directly from `ML_BSSN` making it impossible to use with another spacetime evolution code eg `Baikal` or `Lean_Public`. The quantities used seem to be the Hamiltonian and momentum constraints.

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[Zach Etienne]

Hamiltonian and momentum constraints – use CCTK_VarDataPtr(string), passed in as parameters

[Leonardo Werneck]

Hi! I’ve been working on a patch for VolumeIntegrals_vacuum and following Zach’s suggestion I came up with the following “draft”:

const CCTK_INT timelevel = 0;
CCTK_REAL* H_gf   = NULL;
CCTK_REAL* MU0_gf = NULL;
CCTK_REAL* MU1_gf = NULL;
CCTK_REAL* MU2_gf = NULL;
if( CCTK_EQUALS(evolution_method,"Baikal") ) {
  H_gf   = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"HGF"  ));
  MU0_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"MU0GF"));
  MU1_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"MU1GF"));
  MU2_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"MU2GF"));
}
else if( CCTK_EQUALS(evolution_method,"ML_BSSN") ) {
  H_gf   = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"H" ));
  MU0_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"M1"));
  MU1_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"M2"));
  MU2_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"M3"));
}
else if( CCTK_EQUALS(evolution_method,"LeanBSSNMoL") ){
  H_gf   = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"ham"));
  MU0_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"mcx"));
  MU1_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"mcy"));
  MU2_gf = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel,"mcz"));
}
else {
  CCTK_VError(__LINE__, __FILE__, CCTK_THORNSTRING,
              "Unsupported ADMBase::evolution_method: %s."
              "Supported methods are: Baikal, ML_BSSN, and LeanBSSNMoL. ABORTING.",evolution_method);
}

The idea would then be to use the variables H_gf , MU0_gf, MU1_gf, and MU2_gf throughout the thorn, instead of variables which are specific to the evolution method chosen.

I don't have much experience with CCTK_VarDataPtr , so any suggestions would be appreciated.

Thanks!

[Zach Etienne]

Hey @Leonardo Werneck . I chatted with Roland about this. He says

The code itself is actually nice to read, just the method is not going to be quite what we want (and I *like* the fact that he reports with VError that he received unexpected input!).

The above code has a couple problems. First, if the gridfunction name changes in any of the above thorns, then we’ll end up getting errors. Second, the gridfunction names themselves must be “fully qualified”, meaning “ham” → “LeanBSSNMoL::ham”, etc.

Roland suggests that we instead require the users to pass the names of gridfunctions through the parameter interface; e.g.,

H_gf   = (CCTK_REAL*)(CCTK_VarDataPtr(cctkGH,timelevel, HamiltonianVarString)); // HamiltonianVarString is defined in param.ccl
if(!H_gf) {
  CCTK_VError (__LINE__, __FILE__, CCTK_THORNSTRING, "Couldn't get data pointer of input array variable '%s' ", HamiltonianVarString);
}

… and similarly for momentum constraints. I’d put in ML_BSSN variable strings as default in the param.ccl; e.g., HamiltonianVarString = “ML_BSSN::H” as default

[Zach Etienne]

https://bitbucket.org/zach_etienne/wvuthorns_diagnostics/pull-requests/4

• Fixes this issue
• Adds long-awaited ADM volume integral support (mass, J, and linear momentum)

(Patch authors: Leo Werneck & Ian Ruchlin)

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[Roland Haas]

Please apply.

[Zach Etienne]

PR reviewed, approved, and merged.

[Roland Haas]

Applied as git hash a937556 "Merged in issue2491fix (pull request #4)" of wvuthorns_diagnostics