Dropping agents?

[Barry McMullin]

Does anybody know of any general problems with *dropping* agents
in the course of a swarm simulation?

I *know* that if there is a probe on an agent, and the agent is
dropped, that will typically (always?) cause a crash.  I also
know the swarm team have plans to put in some more sophisticated
memory management machinery to deal with this problem.

But I now have something different in mind...

I have a toy application, derived from heatbugs.  I want to
arrange for bugs to (occasionally) disappear - be dropped.

I was alert to the following:

  o The bug had better be removed itself from its space.
  o The bug had better be removed from the list of bugs maintained
    by the model swarm.
  o Of course, for the time being, I'd better not have any probes
    on any bug that may have to be dropped.
  o *Then* it should be safe to drop???

  o NB: I do *not* take any special measures to do with "unscheduling"
    any activities on the bug - because my understanding is that this is
    being driven from the bug list; so I (naively?) assume removing
    the bug from that list looks after this....

But: the simulation crashes the first time a drop is tried.

My initial (wild?) conjecture is that the activity scheduler, which
traverses the bug list (sending them each a -step message) gets confused
if the "currently stepping" bug gets dropped from this list.  I
have not attempted to study this possibility in any detail yet - 
and the real explanation may yet be infinitely simpler.  But before
rolling up my sleeves and getting down into the swa(r)mp, I thought
I'd ask if anyone else out there has models with agents being
dynamically created and *dropped*, and, if so, whether you might
have any clues for me?

Thanks,

Barry,


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| Barry McMullin, Autonomous Systems Group,  |    address@hidden |
| School of Electronic Engineering,          |  Voice: +353-1-704-5432 |
| Dublin City University, Dublin 9, IRELAND. |  FAX:   +353-1-704-5508 |
| http://www.eeng.dcu.ie/~mcmullin/home.html |                         |
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