Under the Hood: Simulation Inputs

Here is a look at the input files that go in to a DIRSIG simulation.

Each icon in the dirsig_edit tool corresponds to an XML file:

Behind the scenes, these files are given the following extensions:

• .scene
• .atm
• .platform
• .ppd
• .tasks
• .options

The options file is, by happenstance, optional.

So what goes in to the ".sim" manifest file? It's simply a list of the files assigned to each component. A typical sim file looks as follows:

<simulation>
<scene externalfile="../../warehouse.scene" />
<atmosphericconditions externalfile="./warehouse.atm" />
<platform externalfile="./warehouse.platform" />
<platformmotion externalfile="./warehouse.ppd" />
<tasklist externalfile="./warehouse.tasks" />
</simulation>

See? Nothing more than a list of files.

You can also see the relationship between files and components from within dirsig_edit. Just select Tools -> View summary.

When doing trade studies, understanding the relationship between files and components can make your life easier. You can run DIRSIG on a sim file from the command-line using:

prompt% dirsig -xml foo.sim

You can also skip the sim file and specify the individual component files directly:

prompt% dirsig -xml foo.options foo.scene foo.atm foo.platform foo.ppd foo.tasks

If you don't have an options file, just use a pair of empty quotes:

prompt% dirsig -xml "" foo.scene foo.atm foo.platform foo.ppd foo.tasks

For running a trade study with ten different atmospheric conditions, you can write a shell script which uses this component syntax, passing in a different ".atm" file each time.