Re: [Swarm-Support] Multiple Agents in One Cell

[Sven N. Thommesen]

Crile,

I remember having similar problems myself a while back (in 1997!) and 
I created some extensions to Grid2d for the purpose. These may be of 
use to you. They are found in the 'contrib' directory for Swarm 
contributions, but the file is so small I just appended it here. Hope 
you find it useful. (You should be able to extend the procedures that 
calculate neighborhoods to figure your slopes ...) Of course, the 
code may need to be tweaked a little to work with the latest release of Swarm.

Cheers,
Sven Thommesen

At 11:23 AM 8/24/2005, you wrote:
> 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?"
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SvenSpaces-970805.tar.gz
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