[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 rhaas):

 The hdf5 files (checkpoint as well as regular hdf5 output) already all
 contain a dataset "/Parameters and Global Attributes/All Parameters". For
 example the yt reader would use this information to present it to the user
 or to construct units or the grid structure. It may also be useful to
 obtain the equation of state information that way or minimum temperature
 or atmosphere density. Right now only some information is present in the
 hdf5 files (namely only those parameters that were steered) by default. I
 am not sure if Ian's Mathematica based postprocessing system parses
 parfiles or not. If it does it may benefit from being able to parse the
 better formatted "/Parameters and Global Attributes/All Parameters"
 dataset instead (since it already has all substitutions performed,
 comments removed, special characters escaped).

 Right now the parameters dataset is output each time a dataset is written
 to the file, overwriting the previous "/Parameters and Global
 Attributes/All Parameters" dataset. It would be better (as indicated in
 the ticket) to actually save the history of parameter changes.

 I do not know on top of my head if (or which) of our hdf5 manipulation
 tools copy this dataset. I would expect that hdf5_extract likely does
 (since it copies datasets recursively) but eg hdf5_slicer may not.

 All the information that characterizes a run should (I think) be in the
 parameters (since they are the only thing that initially describes the
 simulation to the code). Tabulated initial data and equation of state
 tables are separate files but the file names are mentioned in the
 parfiles.

 The HTTP thorn can steer parameters based on user input which would show
 up as a regular parameter change.

 It may not be possible to exactly reproduce the state of the parameters at
 each moment in the simulation if eg a parameter is steered more than once
 during the same iteration or steered (for identical iteration number)
 after some refinement levels are already processed. This situation is
 similar to other Cactus output however.

 We will need some discipline to prevent users from using parameters as
 evolving quantities since with these changes a parameter that is steered
 at each iteration effectively becomes a grid scalar.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1565#comment:3>
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