How to create the model-artefacts for the two Netlogo simulators.

Example with two Netlogo random walk models

The models used are a simple random walk where, for each simulation step, agents (so-called walkers) choose a random direction and step forward. In our example, the walker can go from one model to another. That is, we define one boundary in each model, when a walker cross that boundary, it is sent to the other model.

The Netlogo models specifications available here and here. The exchanged data will be here the walkers positions (x,y) and the walker ID.  The output port of one model is linked to the input of the other.

random walk example 2


Implementation : model-artefact

The process is very similar to the one describe in the previous tutorial (extend the Interface GenericModelArtefact). We just need to add methods in each model-artefacts in order to deal with the deletion and the addition of a walker in the model.

Functions

Add (remove) a walker to (from) a model

Since I found that Netlogo had a strange behaviour with the "die" command, I use "ht" and "st" (hide and show turtle commands) to make the walkers disappear (appear) from (to) a model or. This is a hack due to Netlogo, if you want to do the same with another simulator, be sure that your simulator implement a method that allows you to add or remove an agent (e.g. a walker, a turtle...)

  /**
   * Add a turtle in the center
   */
  private void addWalker(Walker tortuga) {
    
    String cmd = "ask walker "+tortuga.getID()+" [ setxy 0 0 st set heading " + tortuga.getHeading() + " ]";
  
    try {
      App.app.command(cmd);
    } catch (CompilerException e) {
      e.printStackTrace();
    }
  }

  public void removeWalkers(ArrayList<Walker> walkersToRemove) {
    for (Walker tortuga : walkersToRemove) {
      removeWalker(tortuga);
    }
  }

  private void removeWalker(Walker tortuga) {

    String cmd = "ask walker "+tortuga.getID()+" [ ht ]";
   
    try {
      App.app.command(cmd);
    } catch (CompilerException e) {
      e.printStackTrace();
    }
  }

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