[Repast-developer] Topology Notes

[North, M. <no...@an...>]

Tom:
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The topology issues that we discussed might be represented as follows:
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1.)    An abstract Topology class or interface can be defined:
a.       The class has a method, getDistance(Object o1, Object o2), =
that
returns the distance between any two objects.
b.      The Topology class has appropriate methods to get neighbors =
within a
certain range such as getNeighbors(Object o1, double range) .
2.)    Three or more concrete Topology implementation classes can then =
be
defined:
a.       An implementation for Moore neighborhoods, von Neumann
neighborhoods, and hexagonal neighborhoods based on the current grid
implementation can be defined.  This would use the current array-based =
grid
storage and maintain backward compatibility.  Since it is essentially =
the
current implementation, it would run as fast as the current code.
b.      An implementation for metric spaces can be defined that uses =
trees
to store objects and find neighbors.  This can be done since the rules =
of a
metric space allow tree storage.  For example see
http://www.vldb.org/conf/1997/P426.PDF
<http://www.vldb.org/conf/1997/P426.PDF> .  Other implementations are =
also
available, especially for large lists.  For example, see
http://portal.acm.org/citation.cfm?id=3D328959
<http://portal.acm.org/citation.cfm?id=3D328959&dl=3DACM&coll=3Dportal>
&dl=3DACM&coll=3Dportal.  This implementation would run slower than the =
current
code but it would still be reasonable for most problems.  The price of
slower execution is made up for by the added flexibility.
c.       An implementation for completely abstract (i.e. non-metric) =
spaces
can be defined that uses a simple list to store objects and a na=EFve =
all
pairs matching algorithm to find neighbors.  The algorithm will simply =
test
the distance between each object to find neighbors.  This =
implementation
will be much slower than the current code for large lists but the =
slower
execution will be made up for by the increased flexibility, at least =
for
initial testing.  Users that find they need a particularly abstract =
notion
of space are free to develop optimized versions of the Topology class =
as
they see fit.
3.)    Users select the fastest concrete implementation class that =
supports
their model's notion of space.  Of course, users are also free to =
extend or
add to the existing concrete classes.
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Mike
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