Active Walker Code Page

Code Description

This active walker code simulates walkers moving across a lattice, on which food is randomly distributed. Each walker modifies the landscape by dropping a pheromone, which all walkers may interact with. This interaction algorithm can be easily modified to represent simple active walkers, random walkers, or two-pheromone ant models.

In order to compare properties, the program continuously drops food on the lattice, and allows pheromone and food levels to steadily decay at an adjustable rate. This allows the system to reach a steady-state, so that equilibrium properties can be compared.

Code Features

Input Parameters:

• Total number of food
• Number of steps
• Number of food particles/site
• Number of walkers
• Food addition rate
• Number of pheromones (1 or 2)
• Pheromone interaction strength(s)
• Food decay rate
• Pheromone decay rate
• Greyscale normalization value for the Postscript output file
• Postscript output resolution
• Probability of forward (inertial) walks
• g(r) binwidth
• Initial random seed
• Lattice type (square or triangular)

Output Properties:

• Food collection efficiency (formatted for Analyzer)
• Diffusion rate (formatted for Analyzer)
• Number of food particles as a function of step
• Food distribution function g(r)
• Postscript plot of number of hits/lattice site
• AtomViewer-viewable coordinate files

Download the code

walk.f

walk.cm

walkps.f

run1.in

If npher is set to 2, then it uses the following two-pheromone model:

• Scouts without food: emit A, random walk
• Scouts with food: emit B, react with A
• Workers without food: emit nothing, react with B
• Workers with food: emit nothing, react with B

twalk.f

Twalk is the trunk trail walking model:

• Scouts without food: emit A, react with A
• Scouts with food: emit B, react with A
• Workers without food: emit A, react with B
• Workers with food: emit B, react with A

Use the same walk.cm and walkps.f from above.

wwalk.f

Wwalk is the hybrid walking model.

• Scouts without food: emit A, repel from A
• Scouts with food: emit B, react with A
• Workers without food: emit nothing, react with B
• Workers with food: emit B, react with B

Use the same walk.cm and walkps.f from above.

f77 -c walkps.f

f77 -o walk walk.f walkps.o

Then run it by typing walk.

Or, you can use a little csh script I wrote makeit -- just put it in the directory with the program files and type

chmod u+x makeit

to make it executable. (It just runs the above two commands -- handy for saving yourself some typing.)

I'd strongly recommend also setting the optimization flags to their maximum values. For the EWS HPs, the flag is +O2 (e.g. f77 +O2 -c walkps.f). (The maximum optimization is +O4, but we were having some problems at first. It hasn't been tested since, so use at your own risk.)

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