The Kim-Ostlund torus map undergoes many bifurcations as the parameters are changed [4], [5], [6]. In investigating the behavior of a complicated dynamical system, researchers often find it convenient to save system information associated with interesting dynamics. In this section we will save information about the torus map to a file and then retrieve the information.
If necessary, open the Selected Point panel using
on the Settings menu button of the dstool command window.
Clear the 2-D Image window with
.
Then change the value of wx to
0.5 and change the value of wy to 0.8.
Generate a phase portrait for these parameter values.
(See figure
.)
Suppose that you wish to save this phase portrait. With dstool you have several options. The first option (the default) is to save only the information about the phase portrait. This includes the name of the dynamical system being studied, the parameter values, values of some tolerances used in numerical computations, and a few lines worth of other information. The default option does not save any data points. The advantage of this option is that it does not require the storage of the large amount of data which actually comprise the phase portrait - yet the phase portrait may be fully reconstructed.
Using
on the File menu button of the command
window, select the menu entry Save... to open the
Save panel. Edit the Directory: and Filename:
fields appropriately to set the name of the data file in some
directory where you have write access.
Options specify exactly which data is saved. Use
to
toggle these choices on or off. Choices are boxed within darker
rectangles when they have been selected. In this case,
the
option Current Settings. Now click
on the Save
button at the bottom of the panel to actually save the data.
To reload this data at some later point, open the Load panel
by selecting with
the Load... menu entry button of
the File menu button on the command window. Edit the
Directory: and Filename: fields to the same choices
you made before. Maintain the option dstool Format right now.
( The dstool Reference Manual describes how to import
unformatted data into a dstool memory object. ) Clicking
on the Load button will then restore the dstool settings.
We remark that saving and loading trajectory data is significantly slower than merely saving the Current Settings values. The length of time needed to save or load data depends on the number of data points, the dimension of the phase space, and the particular machine running dstool.