[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 eschnett):

 Roland: We tried storing parameters as attributes, and found that this has
 a large size and time overhead. This was unacceptable, and we thus had to
 revert this change. We also used to output much more information about the
 grid structure, but also had to remove this output again, for the same
 reasons.

 Mapping to the respective HDF5 types is trivial; the respective
 functionality exists in Carpet, based on C++ templates.

 We can certainly change the format of multi-line strings in Formaline. The
 current format is similar to the one used in Cactus parameter files.

 Cactus generates parameter files in the output directory. If there is no
 option to generate all parameter values (including the defaults), then we
 should add this. I would like to add that having the original parameter
 file around is also important, since it often contains comments that are
 useful to know later on, even if they are not usable in visualization
 scripts.

 Instead of parsing parameters, would it make sense to output more
 information regarding the grid structure? The grid structure should be
 easier to parse (or can be modified to be so), and is the only
 authoritative information anyway. The influence of parameters on run-time
 decisions is often very indirect, e.g. they may be ignored after
 recovering. In particular for post-processing or visualization, I think
 you should be looking at other sources of information, and we should add
 these to make this possible.

 Ian: The config-format does not easily handle multi-line strings, or
 strings with beginning/trailing white space. I designed the parameter
 storage format to be similar to Cactus parameter files. If we want to be
 able to use the config-file format, then we should probably at the same
 time design a parameter file format for it. I am not particularly fond of
 multi-line strings or leading/trailing white space, so we may just do away
 with them at the same time, and design better mechanisms to handle long
 lists (of thorns or variables) in parameter files.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1565#comment:15>
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