Refining the diagnostic output system

[timspainNERSC]

The current ConfigOutput system works fine, but we will soon be adding XIOS. This will allow more complex specification of diagnostic outputs. This issue is the place to discuss what the future output system of nextSIM-DG will look like.

[timspainNERSC]

My current thoughts on where development should go:

• The set of diagnostic outputs should be able to be specified at runtime, preferably by only changing the configuration options in the config file or on the command line. This is currently how ConfigOutput works, but I would like to maintain that functionality when XIOS and its XML files are added. This might involve a wrapper script around the nextsim executable to create the XIOS files. Such a script might be needed anyway to launch the XIOS server &c.
• Some way to specify how much output is passed to ConfigOutput/XIOS. My understanding is that XIOS expects all of the fields to be passed to it, and filtering is done internally. Considering that we might want to provide a large number of debug outputs, some way of setting this might be useful.
• But a user is unlikely to want to choose regular/debug levels of output globally, but rather on a per component basis. This would imply a few things:
  • Configuration options for anything that has a variable level of input.
  • More parts of the model become configurable, increasing class complexity. But this would have to increase in any case to allow selectable levels of output.
  • The available fields are now visible in the config help system, so an additional help system laying out the available fields is not necessary.
  • Common code for the detail switching can be placed in a base class, something like ConfiguredOutputComponent, inheriting from both ModelComponent and Configured.

The workflow might then be:

1. The user consults the documentation or the config help system to determine which output fields they require. This information includes the field name used by ConfigOutput and XIOS.
2. The user adds this information to the config file or the nextsim command line.
3. For XIOS, this information is processed by a script to generate the necessary XML files.
4. The classes supporting output are configured to generate the requested output.
5. During runtime, all configured fields are forwarded to ConfigOutput/XIOS every TS, where the necessary output processing occurs.