Running models

Once you have drawn the model diagram and
specified how to calculate the value of each element, you are ready to
perform a simulation. During the simulation, the model is run for a
specified number of time steps, and the changing values of any of the
elements can be plotted, recorded in tables, or displayed using a variety
of other visual tools. You can develop your own displays specific to the
needs of your models.

Preparing models to run

Before it runs a model, Simile generates
an executable program from the model diagram. It does this in response to
the ModelRun command.

• Running
  models

Run time environment

Simile provides two alternative
environments for running models and seeing the results of the simulation.
The standard one uses a single window containing a number of panels: one
for controlling the simulation, another for any input sliders, and others
that can contain graphs or other ways of visualising model behaviour. The
alternative, multiple-window environment has a separate window for each of
these.

You decide which of the two run-time
environments you want by ticking or un-ticking the option "Single-window
Model Run Environment" in the Preferences dialogue window, obtained by
selecting the Preferences item in the Edit menu.

• Single-window
  Model Run Environment

• Multiple-window Model Run Environment

Controlling model execution

Whichever execution environment you choose, you control the model's
execution via the run control panel. This is
either a special box within the single execution window, or a whole window
itself, but looks the same in either case. It allows you to:

• start, pause and reset the model's execution,

• set the time for which it will execute and the frequency of display
  updates, and

• adjust other execution variables such as the step size and integration
  method.

Visualising model behaviour

The term "helper" is the generic term in
Simile for any tool for displaying model behaviour (i.e. the values for
variables), or for entering values into a running model.

• Working
  with helpers

Parameter estimation and predictive
analysis

Simile incorporates an interface to
the PEST parameter estimation
tool. This carries out parameter estimation by varying model parameters in
order to match model behaviour with measured data from the system being
modelled. It can generate prediction ranges for model outputs based on
combinations of parameter values found in this way.

• Working
  with PEST

Working with external data

If your model has variables whose data
source is chosen as being from file, i.e. so-called "file parameters", then
it requires data to be provided before the simulation can proceed. A file
parameter dialogue window will appear to enable you to provide the required
information.

• Working
  with external data

Scripting model execution

In addition to the interactive run-time environments, a scripting
interface is provided to enable simulations to be run without user
interaction. This is often useful for simulation experiments, e.g. running
the same model for a set of scenarios (probably defined by parameters in a
scenario file), for sensitivity analysis or
parameter estimation.

• Scripting

In: Contents