🚀 go-pugleaf

From fishwick Thu Apr 21 16:08:29 1988
To: fishwick < ~/sim/header1
Subject: testing


Volume: 1, Issue: 2, Thu Apr 21 17:01:27 EDT 1988

+----------------+
|    CONTENTS    |
+----------------+

(1) Simulation at Politechnical University of Catalonia
(2) In the Boxing Ring: Simulation vs. Closed-Form




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Date:     Tue, 19 Apr 88 19:51 N
From: <EARAFAEL%EBRUPC51.BITNET@cunyvm.cuny.edu>
Subject:  SIMULATION DIGEST
To: simulation@ufl.edu
X-Original-To:  sim_topic


    My best wishes to the "comp.simulation" subscribers and moderator.

    I just want to introduce a few ideas:

        1) We think that it would be interesting to know the people or
           organizations subscribed to the simulation news group.
           i.e. to have a short 'curriculum' of them  (name,
           ordinary mail address, e-mail addresses, research
           activities, topics of interest, simulation tools used or
           being developed,...).

           So, I'll introduce myself:

           *-  Name     : Antoni GUASCH
               O-mail   : Cybernetics Institute
                          Polithechnical University of Catalonia
                          Diagonal 647
                          08028 Barcelona - SPAIN
               Phone    : (343) 2492842
               E-mail   : earafael@ebrupc51.bitnet

            *- Sim. research activities :
                        - Research in continuous or piecewise continuous,
                          hierarchical simulation languages.
                        - Object oriented languajes and expert systems in
                          modelling and simulation.

           *-  Topics of interest :
                        - Real time simulation
                        - Expert systems
                        - Object oriented programming

           *-  Simulation tools used :
                          ICDSL (CSSL-like) and SIMSCRIPT

           *-  Simulation tools being developed :
                          MUSS (hierarchical simulation environment)

           *-  Some recent activities:
                        - Organisation of the IMACS International Symposium
                          on "AI, Expert Systems and Languages in Modelling
                          and Simulation".   Barcelona, June 1987
                        - A study on simulation and modelling:
                          "future satellite simulators" for
                          the European Space Agency.

           *-  Miscellaneous :
                          The Institute has three main research areas:
                          Automatic Control, Bioengineering and
                          Robotics. Simulation is a master piece
                          to deal with complex electrical networks
                          and bioengineering models.
                          The simulation group provides support and tools for
                          the Institute modelling and system analysis. It
                          also gives courses on Simulation in the Politechnical
                          University of Catalonia.
                          The simulation group is composed by 4 people:
                          Prof. Rafael M. HUBER (in charge of the simulation
                          group), two undergraduate students (Carles MUNTADA and
                          Jose Manuel MARTIN) and myself (Associated Prof.).

        2) Designing and coding a new robust simulation 'environment' is not
           an easy task. It involves aspects such as:

                     - formal language definition
                     - compiler-compiler techniques
                     - numerical integration
                     - state and time events management
                     - sorting or event scheduling problems
                     - model or experiment data bases
                     - graphical or numerical postprocessors
                     - drivers for different peripherals
                     - documentation management

           For a small group its quit difficult to cover all of these
           aspects. Moreover, a lot of time is spent designing modules
           or routines which have been already coded by somebody else.

           Thus, I feel that it would be very interesting to create
           macro-groups (M-GROUPS) interested in joining efforts and
           developing specific tools.

           I wonder if this is possible.

           I will appreciate ideas and comments about this point.


                                              Bye,  Toni
                                                   --//--

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Date: Thu, 21 Apr 88 16:52:03 EDT
From: Paul Fishwick <fishwick@fish.cis.ufl.edu>
To: simulation@ufl.edu
Subject: static analysis vs. simulation


How about some controversy?! I just recently got back from the
SCS Eastern Simulation Conference in Orlando and was interested
in several of the topics that arose from panel discussions and
talks. In particular, Ramana Reddy made a comment during his
plenary talk that I found very interesting...he questioned the
notion of "simulation being the *last* resort" in solving hard
problems. I agree with Ramana that this notion of "last resort"
is often incorrect. Perhaps many of you have your own thoughts
about whether simulation as a problem solving method should be
considered "a last resort." Why not a first resort! There are
many sub-issues here...I'll list some that I can think of:
(disadvantages are identified with '-' and advantages are identified
with '+'):



METHOD: CLOSED-FORM SOLUTION (i.e. static analysis)

(+) often very fast since it involves equation solving. Good example
    is queueing models (with many assumptions!).

(-) you obtain a steady state solution (which might be all that
    is required!).

METHOD: SIMULATION (i.e. dynamic analysis)

(+) extremely flexible. Can handle very large and complex scenarios.
    you obtain a transient solution.

(-) slower than closed-form in some circumstances. Also, many
    claim that it "costs more."

Here are some debatable notes:

1. Remember when calculators were larger than bookcases? At that time,
people probably said...use calculators as a last resort----but first,
see if you can solve the problem using your handy dandy slide rule.
Perhaps this issue of "simulation as a last resort" falls into the
same category. As hardware becomes cheaper and faster--there will be
less and less problems that will necessitate closed form solutions.
What is the percentage of problems now that require a closed-form
approach as a first try in problem solving? 30%, 2% ? Are there certain
domains or application areas that favor a closed-form approach?

2. As companies are coming out with visually (and object) oriented
simulation products, will simulation always *cost* more than picking
out formulas from someone's textbook on closed-form problem solving
methods? What exactly are these "costs"?

3. With closed-form methods, many assumptions must often be made to
make the problem solving process mathematically tractable. When we
make these assumptions, are we diluting our analysis and results?

4. Perhaps programs with combinations of simulation and closed-form
methods are best?

How 'bout some lively discussion?

Paul Fishwick
University of Florida


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