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From: fishwick@fish.cis.ufl.edu (Paul Fishwick)
Newsgroups: comp.theory.dynamic-sys
Subject: Re: Dynamic System Simulators (request)
Keywords: simulators
Message-ID: <24395@uflorida.cis.ufl.EDU>
Date: 11 Sep 90 01:55:05 GMT
References: <880@h.cs.wvu.wvnet.edu>
Sender: news@uflorida.cis.ufl.EDU
Organization: UF CIS Dept.
Lines: 98

In article <880@h.cs.wvu.wvnet.edu> schiebel@cs.wvu.wvnet.edu (Darrell Schiebel) writes:
>
>	Could anyone out there recomend dynamical system simulators,
>	especially public domain simulators?  I would really appreciate
>	any responses.
>
>
>	Many Thanks,
>
>	Darrell Schiebel
>	(schiebel@a.cs.wvu.wvnet.edu)
>	(UN027714@wvnvaxa.wvnet.edu)
>	(drs@baks.bell-atl.com) 

You can try out the differential equation part of SimPack. Here is some
info on it. To get the package do an ftp according to these instructions:


* Archives available via FTP to bikini.cis.ufl.edu (128.227.224.1).
  Login as 'ftp', use your last name as the password, change
  directory to pub/simdigest. Do 'type binary' before any file xfers.
* Simulation Tools available by doing above and changing the
  directory to pub/simdigest/tools. 

-----------------
Documentation on DEQ:

IMPORTANT: To take advantage of this software (DEQ), you need the following
on your UNIX system: 

 (1) grtool - an interactive graphics plotting package for all plotting
     functions. grtool is in the simulation tools library at the University
     of Florida, and can be freely FTP'd. Follow the instructions by
     looking at the beginning of each Simulation Digest Issue
     (comp.simulation).

 (2) gcc - one of the primary source routines is written in ANSI C. The
     c compiler 'gcc' is available freely from the Gnu Free Software 
     Foundation. See the file 'gnu.software.Z' also in the UF simulation
     library. This will give you information on how to get 'gcc'.

To make DEQ, do a 'make all'. Then you can run 'deq' from the
UNIX command line as follows:

%deq

You have the choice of entering one of two types of systems. Either

  (1) a single equation with high order terms (derivatives). Note
      that the system may be homogeneous or non-homogeneous, and that
      the left hand side of the equation must be the higher order
      term. Note the following notation: use x[1] for the first derivative
      of x with respect to time (i.e. x' or dx/dt), x[2] is the second
      derivative, and so on. x[0] is simply x.

  (2) a set of first order equations for an 'n'-dimensional system.
      You will be prompted for each equation in turn. Here x[1] means
      the first state variable. x[2] means the second state variable,
      and so on.


EXAMPLE 1
---------

An Example of a single equation is to enter:

  x[2] = -16*x[0] + 10*cos(3.7*t)

Note that this equation is x'' = -16x + 10cos(3.7t) using standard
notation. Try plotting this over time (always denoted as 't') by 
specifying 't' as the x-axis variable, and x[0] as the y axis 
variable to be plotted by grtool.

EXAMPLE 2
---------

An Example of the Lorenz System (Phase Plot) is to enter (note: left
hand sides of equations are prompted by DEQ):

  x[1]' = 10*(-x[1] + x[2])
  x[2]' = 28*x[1] - x[2] - x[1]*x[3]
  x[3]' = -2.666*x[3] + x[1]*x[2]

Try plotting x[1] vs. x[2] when prompted for this information.

	
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