[starlogo-users] patch and global variables...

[josh]

Dear Ken,

I disagree with your statement whole-heartedly.  The idea that the
agents can react to the different types of terrain they are standing on
or in front of, etc., is very useful for the simulation/modeling nature
of starlogotng. The /concept/ of patch variables is exactly how this
should be done cleanly. What you suggest could be done internally to
implement the patch variables efficiently and save computing resources,
but as far as the programming interface and programming style go your
suggestion is a not too pretty hack.

While you are correct that sltng is currently confined to a rough grid,
this is only a question of resolution. Digital fotography is also made
up of little squares, but there are simply a lot of them, so a circle
still looks like a circle.

It would be interesting to be able to make the grid variable in size,
then by adjusting the agent size, you could have whichever resolution
you need to model the environment you want. I'm sure the most
sophisticated VR environments we have today still can be  broken down at
the lowest level into tiny pixels, i.e. a grid.


-j

Ken Kahn wrote:
> Your patch variable example points to a shortcoming with the concept of
> patches. If indeed only a few patches are poisoned then why not keep a
> global variable listing the coordinates of the poisoned patches and
> check for membership. The check may take a few extra nanoseconds but you
> don't waste 10,000 memory locations.
>  
> I'm glad to hear that "Patches are a less active part of StarLogo TNG"
> since I dislike the idea of having something that are really agents but
> they can't move. It just complicates the computation model. There can be
> an efficiency argument for low-level support of non-mobile agents but I
> think it is often less efficient to support patches -- e.g. the poison
> example. Also it pushes one's model towards a uniform rectangular grid
> while there are plenty of other ways to model the environment. Maybe
> poison is spread out over circles of radius 10 while other variables are
> at different patch sizes. Patches are too special purpose to be part of
> a language.
>  
> Best,
>  
> -ken
>