Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!simulation
From: simulation@uflorida.cis.ufl.edu (Moderator: Paul Fishwick)
Newsgroups: comp.simulation
Subject: SIMULATION DIGEST V10 N10
Message-ID: <20856@uflorida.cis.ufl.EDU>
Date: 10 Sep 89 23:51:57 GMT
Sender: fishwick@uflorida.cis.ufl.EDU
Reply-To: simulation@uflorida.cis.ufl.edu
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Approved: fishwick@uflorida.cis.ufl.edu

Volume: 10, Issue: 10, Sun Sep 10 19:51:44 EDT 1989

+----------------+
| TODAY'S TOPICS |
+----------------+

(1) Wanted: Greengard Algorithm Code
(2) Acquiring Qualitative Features
(3) Looking for Timed-Step Simulation Reference

* Moderator: Paul Fishwick, Univ. of Florida
* Send topical mail to: simulation@bikini.cis.ufl.edu OR
  post to comp.simulation via USENET
* Archives available via FTP to bikini.cis.ufl.edu, login as
  'anonymous', use your last name as the password, change
  directory to pub/simdigest.
* Simulation Tools available by doing above and changing the
  directory to pub/simdigest/tools.



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To: comp-simulation@uunet.uu.net
Path: sun!bipsco!peb
From: peb@bipsco.Eng.Sun.COM (Paul Baclaski)
Newsgroups: sci.physics,sci.math,comp.simulation,comp.sources.wanted
Subject: Greengard algorithm wanted
Keywords: n-body problem greengard algorithm simulation
Date: 5 Sep 89 20:18:02 GMT
Sender: news@sun.Eng.Sun.COM

I recently ran across the book "The Rapid Evaluation of 
Potentials in Particle Fields" by Dr. Greengard (MIT Press, 1988)
which describes an algorithm that calculates the n-body problem
with respect to gravitational or electrostatic fields such that
the complexity is O(n) rather than O(n^2).  It appears to use
quadtrees and fields.

I would think that if this is possible, source code would be 
available to do this...or at least an understandable description
of the algorithm (the book is rather dry).

Please send me pointers to better descriptions, third party 
analysis or best of all *shareware*/*public domain* software
that implements the Greengard algorithm.  (If you have Greengard's
email address...)

Please send me mail directly since I don't read all these newsgroups.

Thanks in advance,


Paul E. Baclaski
Sun Microsystems
peb@sun.com

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From: Raul Valdes-Perez <valdes@B.GP.CS.CMU.EDU>
Date: Wed, 6 Sep 89 21:44:40 EDT
To: simulation@bikini.cis.ufl.edu
Subject: acquiring qualitative features
Reply-To: valdes@B.GP.CS.CMU.EDU

Greetings.  I am working on automatically extracting qualitative
features from systems of parameterized, nonlinear differential 
equations, in particular the kinetical equations of chemical-reaction
mechanisms.  Lacking any mathematical tools to accomplish this,
I am simulating the equations under fixed initial conditions, while
varying the parameters, in order to acquire invariant features in a
data-driven manner.

Does this sound like work that anyone has done, or is doing?  If so,
I would much appreciate any pointers.  Thanks.

Raul Valdes-Perez
CMU Computer Science Dept.

[[Raul - you might want to reference books in nonlinear dynamics, 
specifically in the area of bifurcation analysis. The invariant
part of a nonlinear system can be characterized as a function of
parameter changes. I'll mention only a couple of sources;
however, there are lots of other potential sources -- seek out
work in systems theory and chaos theory:

 "Dynamics: The Geometry of Behavior" by Ralph Abraham and
 Chris Shaw, Volumes 1,2,3,4: Aerial Press, Santa Cruz, CA.
 [a nice graphical introduction]

 "From Equilibrium to Chaos: Practical Bifurcation and Stability 
  Analysis" by Rudiger Seydel, Elsevier, 1988.

  Also a small plug for an upcoming book (by end of 1989):
  "Qualitative Simulation Modeling and Analysis" edited by
  Paul Fishwick and Paul Luker, Springer Verlag...
 
As far as software, there exist numerical methods for determining
the branch points such as BIFPACK and AUTO. Once you have the
branch points, you can map quality to quantity. Hope this is of some
help. -PAF]]

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Return-Path: <feldy@CS.UCLA.EDU>
Date: Thu, 7 Sep 89 18:56:28 PDT
From: feldy@CS.UCLA.EDU (Bob Felderman)
To: simulation@bikini.cis.ufl.edu
Subject: Looking for reference on Time-Stepped Simulation

Does anyone know of a "classic" reference for time-stepped simulation
on digital computers? Preferably distributed time-stepped.

Bob Felderman                   	         feldy@cs.ucla.edu
UCLA Computer Science   	...!{rutgers,ucbvax}!cs.ucla.edu!feldy



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