Re: [Swarm-Support] How to remove agents in run-time?

[Steve Railsback]

Emerson Aguiar Noronha wrote:
> Hello all,
>
> In my simulation I need to remove agents in run-time, accordling to
> agent's local rules. I've tried to do this using a method implemented in
> the simulation's model. This method is called in ActionForEach, this code
> remove an agent from the simulation's data structures, and I've tried to
> remove it from the actionGroup in many ways.
>
> What happens is that the agent is removed from the grid and from my
> simulation's data structure. However, the swarm action still calls the
> removed agent's step method. I've looked-up for this instance but I can't
> found it.

Hello Emerson,

Are you scheduling the step method using an actionGroup and a statement 
something like: [stepActions createActionForEach: agentList message: 
M(step)] ?

To remove an agent so it no longer gets it's "step" method called, you 
need to remove it from the list used in the "createActionsForEach" 
statement (in the above example, "agentList"). (You also still need to 
remove it from all the grids and other data structures.)

Unfortunately, you cannot remove the agent from the list while the 
actionGroup is still executing: an agent cannot be removed from the 
agentList during it's "step" method, because that messes up the 
scheduler as it goes through the agentList telling each agent to do "step".

So the usual approach is, during "step", to put the agent to be removed 
on a list of dead agents. Then, add a separate action that happens after 
"step" that removes all the dead agents from the model.

There is an example in Version 12 of StupidModel, which you can get here:

http://condor.depaul.edu/~slytinen/abm/StupidModel/

Steve Railsback