[ET Trac] [Einstein Toolkit] #1565: change default of IOUtil::out_save_parameters to true

[Einstein Toolkit]

#1565: change default of IOUtil::out_save_parameters to true
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  Reporter:  rhaas        |       Owner:                     
      Type:  enhancement  |      Status:  review             
  Priority:  optional     |   Milestone:                     
 Component:  Cactus       |     Version:  development version
Resolution:               |    Keywords:                     
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Comment (by hinder):

 One thing I have been considering recently is that we could set the
 parameter IO::parfile_write = "generate", which I believe causes the
 parameter file written into the simulation output directory to includes
 all current parameters and their values, not just those explicitly set by
 the user.  This would allow SimulationTools to obtain the actual values of
 various parameters, without having to have knowledge of their defaults.
 This would be stop-gap measure until there is a proper metadata file
 written by Cactus.  SimulationTools would still have to interpret the
 parameters, attempting to make sure that it has the same logic as Cactus,
 so a proper "low-level" metadata file generated by Cactus would still be
 superior.

 SimulationTools works with entire simulations, so it doesn't look at the
 parameters stored in HDF5 files, as it looks instead at the parameter
 file.  Probably most analysis tools deal with gridfunctions directly,
 without needing them to be associated with a simulation.  In that case,
 some of the information which is currently only available in parameters
 might be useful.  On the other hand, I think it only makes sense to store
 information in the HDF5 file which pertains to the variable being stored.
 Things like atmosphere settings are properties of the simulation, not the
 variable, so if you need to know about that, then you should accept that
 you should have been dealing with simulations, not just variables.
 Symmetry conditions apply directly to the variable, as they tell you how
 the full physical variable can be reconstructed from the data, so they
 should be included with the variable in the HDF5 file.  However, I don't
 think that parameters are the best way to go about this.  Instead, I would
 add additional metadata as attributes to the datasets, or in a separate
 dataset just for this information.  Parameters are designed for the user
 to tell Cactus what to do, and there may be several different ways of
 specifying the same information (see, eg. CoordBase).  You don't want to
 have to interpret those parameters; you want the symmetry thorns to tell
 you exactly what they have done.

 As a stop-gap measure however, including all parameters in the HDF5 file
 would probably solve your immediate problem.  I assume it would not make
 the HDF5 file too large, so I don't see any harm in changing the default.
 Changing the default for the parameter file written to the output
 directory would help SimulationTools, but would then mean that generated
 parameter files would be unrecognisable, so it's probably not a good idea
 to force that on everyone by changing the default.  I will probably start
 using this in my own simulations though, as I use simfactory, and hence
 have the original parameter file available anyway.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1565#comment:5>
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