Model States

The state of a model can be saved at any time during the modeling work using a number of methods. The file containing the saved model state is interchangeably referred to using the terms save file, save or saved state, or SAV file (historically, saved model state files use the file extension .SAV).

Saving model states is an important and artful process — how this is done effectively articulates the project design. The numerical modeling project requires development of the model over the timestepping process, however, the program can only represent the model at the present state of cycling. Consequently, a project will almost always comprise a number of save files, which are like stepping stones that trace the path taken by the modeling project. Reviewing “How Data Files Work,” it can be assumed that the modeling process is likely to (or should) produce a set of save files that reflect the hierarchical arrangement of data files that built them: a tree-like linkage of data files creates the project, and a tree-like linkage of save files is likely to emerge from it.

Projects and Model States

See Handling Projects for the basics of saving a project.

File change within the program — whether by opening a new file, closing a current file, or opening an other, pre-existing file — may provoke some prompting if the current file is in an unsaved state. Given the range of files that are under active management in the program (project files, save files, results files, data files, and so on), there are many permutations on the scenarios that can come into play, and they are easily triggered given the number of files under active management in the program. In these cases, a dialog or series of dialogs will provide users options for handling unsaved data.

Results Files

Results files are save files that contain only selected model data, and are smaller, sometimes much smaller, than full save files. They are requested via command or from the i Options dialog prior to cycling. Results files are restored like save files, meaning a results file will become the current model state when restored. However, the model cannot be cycled from that state; in that regard, results files are “read-only”.

Results files are a convenience that provide advantages in the following scenarios.

  • They can provide a more granular tracking of the model during the run, as they represent a second stream of data from the model that is likely to be created more granular than the stream created by the save files.
  • If a model is sufficiently large that restoring individual model states is time consuming, results files can provide a much faster way to move between model states during post-processing analysis.
  • If model output across some length of the model run is needed for export to other tools (for a movie, a spreadsheet, etc.), it is often easier and faster to do so from results files, if all the necessary data can be identified and requested in advance. The program provides a tool for batch processing results files for the purpose of making a movie.