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EMR's picture

Ants and Termites

I looked at Langton's Ant (the NetLogo version, which is called Vants for Virtual Ants) and also the NetLogo model Termites. Vants is fundamentally the same as the Langton's Ant model we examined in class, although the details are a bit different. The NetLogo version does not give you the ability to generate 'roadblocks,' but it does allow you to run multiple ants at once (up to 16) and to run ants in reverse. Also, the ants are not always started on the same heading (pointed in the same direction), so different runs can give slightly different rersults. I found the interactions between multiple ants very interesting- as well as the standard 'roadbuilding,' another pattern emerges wherein one ant 'discovers' the base of a road being built by another, and quickly moves straight down the road and interrupts the roadbuilder. One of the two then moves quickly back along the side of the road, and the other (hard to tell which is which) proceeds to 'erase' the road, moving back along it and reverting all the changed cells. The 'reverse' function makes the ant or ants follow the standard rules but with 'forward' and 'backward' reversed, which gives the same sort of 'erasing,' although not confined to roads. The reversal option demonstrates how the model is deterministic, as the ants eventually all end up back at the origin in a plain field, but then proceed through 'time=0.' You can go back and forth through t=0 and see that the patterns on either side of t=0 are always the same. That is, the pattern moving forward from the origin is always the same, as is that moving in reverse from the origin, but they are not the same as each other. This model demonstartes how simple interactions can lead to the complex 'roadbuilding' pattern.

The Termites model generates a field with colored patches or 'woodchips' randomly distributed throughout at a user-determined density, and a randomly distributed user-determined number of 'termites.' The termites 'wiggle' at random, and when they encounter a woodchip they pick it up, wiggle until they find another woodchip with an empty space adjacent, and set it down in the empty space. Regardless of the initial number of termites or density of woodchips, the termites deterministically end up moving the woodchips into a single large pile (although it can take a long time). Again, a set of simple interactions give rise to a surprisingly deterministic, organized result.

I found that the user controls for the Vants model gave more interesting results than those for the Termites model. However, I liked the more real-world scenario of the Termites model. It helped that the termites are actually intended to look like termites (or at least insects) while the ants were simply portrayed as triangles, but appearance is simply a nice touch, not a necessity for understanding the models.

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