Percy's Alife Project

You don't need to store 10^18 of anything.You only need sufficient memory to store all of the objects
in your univers (which could be large, but not as large as
the universe itself).Instead of defining a temperature across your univers you need
to locate heat sources within the universe and calculate temp.
at any location via some radiant heat function (incorporating
heat absorption by other objects).Each object has a place in the univers, rather than each place
in the univers has an object.Physical charateristics are functions of the objects present.

Why OO ?

As i said in a previous post -- it's not a 3d array that
you are running through -- it's an object list each of
which has a 3d coordinate.The universe doesn't exist -- it's just the space that objects
occupy.I used to write text adventures when I was a kid, and had
two separate mapping techniques one very specific (like exit
to the north goes to location 4 etc.) but also had
infinite deserts and forests all within a single location.
Special actions/objects were then related to locations within
the infinite space within a single location object.

I assume you are referring to processing efficiency ...Using a cellular universe means that no matter how many objects
exist within it it takes a broadly similar time for one cycle
and takes as much memory regardless of density.Viewing the universe as a space which has objects in-it means
you only have to store the objects, and iterate over them for a
single cycle.Can't quit see the efficiency problem -- unless it's about locating
adjacent objects....It's a tradeoff between memory and processing speed (as ever)

I see the problem .... would it help if you re-ordered
your object lists based somehow on coordinates though?Then you only have to check for proximity rather than
adjacent ness and the re-ordering goes in the movement overheads.
Moving on an object-by-object basis would require at most
swapping two array (say) locations per movement....not sure you could do it with a 3d grid ... hmmm ...Maybe still too much though depending on data structures
(and language constraints).

You could narrow the number of objects to search,
eg by distance from a set-point in space,
and while I see that it would always be slower, you
could have an 'infinite' universe in finite memory.Depends which might be the more useful ....Slower assuming that the time to check an empty cell
is negligable. If you have 10^18 cells and it takes
10^-8 secs per cell ... never really thought about this
before so I won't be offended if I'm way off in my thinking [This message has been edited by Peter, 10-13-2003]

Just another thought on the environment model ---do you need to wrap at each extremity of your cube or
should some be boundaries ?Depends what you are modelling I guess.