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Re: fest discussion
From: |
Robert E. Bell |
Subject: |
Re: fest discussion |
Date: |
Tue, 24 Feb 1998 19:36:21 -0800 |
Hey Doug...
I think the model verification discussion is a very good idea. You
can definitely count me in (possibly Melissa)...I'm planning on doing
my model verifications of arborscapes (arborgames grew up and started
using real data ;-) this summer. Are you going to organize it?
Robert
Doug Donalson; wrote:
> Is anyone interested in putting together and discussion
> group on model testing and verification at SWARM fest?
>
> Here is my "take" on it with examples from my research.
>
> One of the most difficult and important aspects of complex
> modeling is that of model testing and verification. It
> falls into two broad catagories, verifying that the model
> is bug free, and determining the effects of what I call
> model infrastructure.
>
> Two examples of the first catagory:
>
> Test individual components:
>
> Ex: I have an agent that in the absence of all other
> effects dies off exponentally so I turn off all
> other effects and confirm that all the individuals
> die off and that the half life time matches the
> death rate.
>
> Compare with simpler models:
>
> Ex: I have a "base line" delay differential equation
> model that provides stability boundries and
> equlibrium values for a set of parameters. I
> developed a second model that is the analog of
> the DDE but with the quantization effects associated
> with requiring the number of individuals to be
> an integer. This is the Stochastic Birth/Death
> or SBD formulation.
>
> If I force my complex model to be "well mixed"
> spatially, then it should match the results of the SBD
> for the same system size and parameter choices. The
> SBD model can then provide the parameter space
> where the quantization stochasticity has a small
> effect on the system dynamics. This allows a
> set of parameters or "parameter space" in which
> my complex model should have very similar results
> to the DDE model.
>
> Bottom line: I find a parameter space that if my complex
> model is working correctly it should provide results
> that match those of an analyticaly (or at least
> numerically) tractable model.
>
> The second catagory has to do with the effects that the
> actual model implimentation may have on the results.
> This is basically worrying about artifacts from model
> structure.
>
> Ex: Any time you design a model around a lattice
> structure you by definition quantize space.
> Does this "minium size" of one square have
> a significant effect on the results?
>
> Ex: When using a synchronous schedule how does the
> ordering of events within a time step affect
> the outcome. For example, if it was a predator/prey
> simulation, if predation always came before prey
> birth you would potentially expect a different
> outcome then if births came before predation.
>
> I know this is long winded, but these are key issues if
> we are to believe and understand the results of complex
> models. Is anyone interested in tossing around problems
> and solutions in these areas? Let me know if anyone is
> interested.
>
> Cheers,
>
> Doug Donalson
>
> ***************************************************************************
> * Doug Donalson * Office: (805) 893-2962 *
> * Ecology, Evolution, and Marine Biology * Home: (805) 961-4447 *
> * UC Santa Barbara * email address@hidden
> * Santa Barbara Ca. 93106 * *
> ***************************************************************************
> * *
> * The most exciting phrase to hear in science, the one that *
> * heralds new discoveries, is not "EUREKA" (I have found it) but *
> * "That's funny ...?" *
> * *
> * Isaac Asimov *
> * *
> ***************************************************************************
>
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--
One word frees us of all the weight and pain
of life: that word is love. --- Sophocles
Earth provides enough to satisfy every man's
need, but not every man's greed. --- M. Gandhi
*****************************
Robert E. Bell
Department of Geography
University Of California, Los Angeles
Email: address@hidden
==================================
Swarm-Support is for discussion of the technical details of the day
to day usage of Swarm. For list administration needs (esp.
[un]subscribing), please send a message to <address@hidden>
with "help" in the body of the message.
==================================
- fest discussion, Doug Donalson;, 1998/02/24
- Re: fest discussion,
Robert E. Bell <=