POLS909      Topics in Methodology: Agent-based modeling
March 15, 2000



Exercise 9.1

These exercises are intend to make you think a little bit about the
Observer Swarm level of a simulation and what can be done with it.

Begin with Heatbugs for whatever version of Swarm you have.  I've
tried many variations on these things, but I can't say that I have
ready made illustrations just sitting around. So if it doesn't run
after you compile it, you might let me see what you have done.

1.  Change the colors of the bugs and the heat in the
    HeatbugObserverSwarm.m file.  Look at the colormap.  That is where
    the system finds colors when an agent does a drawSelfOn: method.
    You see some color numbers are assigned one-by-one, as are 64, 65,
    and when we want a color scale for the heat, we use the scale that
    combines the amount of red, green, and blue.  The numbers for red,
    green, and blue must be between 0 and 1, inclusive.

    Note: in the faq, you can find a link to a list of allowed color names:
http://lark.cc.ukans.edu/~pauljohn/SwarmFaq/SwarmOnlineFaq.html#3.11

2.  Change the code in the Heabug.m so that the heatbug's chosen color
    can change over time.  For example, the color might show the bug's
    level of unhappiness, or anything else.

3.  Compile Heatbugs with the Pixmap support. I realize the README says:
     make CPPFLAGS=-DUSE_PIXMAP
     but on Swarm-2.0.1 in Windows, you have to add it like this:
     make EXTRACPPFLAGS="-DUSE_PIXMAP -DDLL"

     Run that, look it over.  Notice how the pre-processor statement
     alters what the Heatbug does when it is told to draw itself. 

4.  This next step is strictly for entertainment, don't bother if it
    gives you a hassle:

     Find a picture editing program that can save images in png
     format, or you need a converter into png format. png is a free,
     open source alternative to gif.  The Gimp image program can save
     png, and last I heard there was Gimp for windows.  I don't know
     what other editors can output png format stuff. If you look for
     30 minutes and can't find a free one, let the email list know and
     we'll concentrate on it.  When I was a windoze junkie, there was
     a free editor called Lview-pro, I don't know what there is now.
     You might check www.dejanews.com/usenet.

     Make some png files, then rewrite the Heatbug.m file so that
     different bugs use different pixmaps.  You could write it so the
     pixmap is assigned by the ModelSwarm.

     This step is just for fun, I've done it and it is entertaining. 

5.   Create more lines to be displayed in the graph output of the
     Heatbugs program.  I think you could make the bug calculate a few
     more things, and give back information about them.  Where you
     currently have getUnhappiness, for example, you could add methods
     to getIdealTemp or such.  Then in the HeatbugObserverSwarm.m, you
     add those variables to the EZgraph.  Its almost obvious what you
     do--just more lines like the unhappy graph.

     Swarm has built-in colors for the lines. If you don't like the
     colors, you can control them. I just added an entry in the
     SwarmOnlineFaq about how.

6.  Try this: Get your Exterminator code from Exercise-8.1, and try to
     integrate it with Heatbugs.  You can look at the examples in the
     Exterminator directory too. I think the Exterm3 is pretty close
     to what you want.  When you compile with Pixmaps, Heatbugs should
     be ready to go, but the Exterminator class will need to be fitted
     in the same way with a pixmap.  I will give you a pixmap for the
     Exterminator if you ask me.  So you can see a raster with
     pictures of exterminators and bugs.  I think that would be
     beautiful.


     7.  Take a look at the game of life. There are tons of web
         sites. A lot of them crash my web broswer.  This one doesn't.
         This is a page where a java applet runs and you can color in some
	 squares and watch the simulation proceed:

	     http://cgi.student.nada.kth.se/cgi-bin/d95-aeh/get/lifeeng
	 
	 Here is another online life simulation. Works fine for me:
	      http://www.mindspring.com/~alanh/life/
	 If you just want to test drive a CA model.

	 Here are a page on CA that does work:
	 http://www.cs.jhu.edu/~callahan/lifepage.html

	 Just about everything worth knowing can be found there, or in
	 links from there.

	 If you want to write rules for CAs, there are specilized CA
	 packages for windows.  

	 1.  Life32 for Windows 95/98/NT by Johan
		 Bontes(http://psoup.math.wisc.edu/Life32.html). According
		 to Alan Hensel, "This is the best Life program for
		 32-bit Windows. It's extremely fast, powerful, and
		 easy to use. Highly recommended!"
        
         Don't forget to get some "Life patterns" while you are on
         that page.  You must have them, they are like "document"
         files that give rules for your ca. The Hensel package of
         rules is cool!

	 If you don't like that, maybe you like this:

	 2. Lou Gross, a well known ecologist at Tennessee, wrote this
	 to me when I asked him "what is the easiest/best windows
	 package for CAs and game of life":
	 
	"Have you looked at Rudy Rucker's Cellab at
	 http://www.mathcs.sjsu.edu/faculty/rucker/cellab.htm It is
	 perhaps not the easiest to use, but most of the real easy
	 ones don't allow easy changes of rules- they just display
	 game of life or others and let students change starting
	 sets."

	 This one comes with some life rules and has a manual. It
	 doesn't look as good as Life32.