[ET Trac] [Einstein Toolkit] #1284: Want stand-alone parameter parser

[Einstein Toolkit]

#1284: Want stand-alone parameter parser
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  Reporter:  eschnett     |       Owner:     
      Type:  enhancement  |      Status:  new
  Priority:  major        |   Milestone:     
 Component:  Cactus       |     Version:     
Resolution:               |    Keywords:     
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Comment (by hinder):

 I'm still not quite sure what you want to use this for, so I can't see
 what aspects are important.  Given just a parameter file, it is not
 possible to know the parameters and their values, because you need the
 Cactus source and the thornlist to determine the default values.  Do you
 need this feature just for your own simulations?  If so, you can set
 IO::parfile_write = "generate", in which case you get all parameters (not
 just those explicitly set) in the parameter file written to the output
 directory.  If you (as I) want to know the values of parameters from
 simulation output, then you won't necessarily have the Cactus tree and
 thornlist, which is why I wrote comment:4.  If you want to know the
 parameters for a parameter file when you do still have the source tree
 etc, a utility or the Cactus executable would be suitable.  For this, you
 would need to be examining the parameter file on a machine where the
 Cactus executable or utility has been compiled with the correct source
 tree.  I suggest that the code in Cactus which parses the parameter file
 should not be duplicated but should be reused.  Given the discussions
 about adding high-level features to the parameter file, and the fact that
 you say you want to know the parameters and their values, a "parser" is
 not sufficient.  You also need something which interprets the parse tree
 and evaluates expressions etc.  If the code in Cactus which performs all
 this logic (and which reads the CCL files etc) is modular enough, then
 maybe it could be compiled into a utility, but I doubt that this is the
 case.  Why do we need mpirun to run the cactus executable?  Can we not
 check the command line arguments and then just not call mpi_init if we
 only want the parameters?  The only time I can imagine not being able to
 run the executable would be if it was cross-compiled.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1284#comment:6>
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