[Swarm-Support] Multiple Agents in One Cell

[Crile Doscher]

Hi there SwarmList,
  I'm trying to work out multiple agents in a cell using lists, as 
suggested by some previous posts (if that doesn't work, I'll try using 
MultiGrid2D).  The primary agents are volumes of water flowing over a 
riverbed (the cell surface, a Discrete2d which contains the cells), so I 
need each cell to hold an elevation value as well as a list of agents.  I 
have borrowed some methods from MultiGrid2d (my thanks to Paul Johnson and 
Opinion2.0).  The elevation values come from an ascii file originating as a 
GIS raster grid and are read into each cell after the agent list has been 
created  but before any agents are added (the collection is created when the 
cell is created, well, during -createEnd a la Opinion, to be exact).  During 
runtime, a method gets called from the agent to the cell surface that 
determines which cell is the best to move to by calculating local slopes 
from that particular cell.  The problem is that where before I could easily 
read in the elevations, calculate the slopes and move the agents around 
(until two ended up in one cell, of course), I now get NaN returned when the 
cell surface queries a cells for its elevation values (and a subsequent 
crash).  A -getCellAtX: Y: method is used to access the cell's elevation 
value - this worked fine prior to implementing the list.  It seems like 
creating the list has either made the elevation value inaccessible, or 
perhaps the list has overwritten them.
  So, have I been sloppy in creating my lists?  My gut feeling is that my 
cells should be able to hold both elevations and lists and I simply haven't 
implemented this well.  Could the order in which the list is added and 
elevation values read in be causing a problem?  Any thoughts?
Thanks -
Crile

Dr Crile Doscher
Natural Resources Engineering
Lincoln University
Canterbury
New Zealand

"What if the hokey pokey is what it's all about?"