simulation@uflorida.cis.ufl.edu (Moderator: Paul Fishwick) (06/16/89)
Volume: 9, Issue: 5, Fri Jun 16 11:54:31 EDT 1989
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| TODAY'S TOPICS |
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(1) Re: Event Unscheduling
(2) The EcoLogic System
(3) Reversable Simulation
* Moderator: Paul Fishwick, Univ. of Florida
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Date: Thu, 8 Jun 89 09:42:30 -0400
From: Paul Fishwick <fishwick@fish.cis.ufl.edu>
To: simulation@ufl.edu
Subject: event unscheduling
The question of unscheduling seems an interesting one; however, it might
be the case that the original model should have a finer time slice
(at least during the boiling of the water) which will avoid the need
for unscheduling of the event "water is now boiling." Let's consider the
scenario provide by Sanjai:
Event # 1. An event putting_kettle_on_stove fires.
Now, given a closed world assumption (that simulation models must have
unless they are distributed among several processors), the modeler must
consider whether it is at all possible that there might be an "interrupt"
that would prevent the logical progression to the event water_boiling (ev. #2)
If so, then the time lapse between event # 1 and event # 2 can be broken
down using a fixed time slice or continuous time method -- thereby obtaining
a hybrid model that is both discrete and continuous in nature. Then the
"interrupt" may be processed accordingly and event # 2 may or may not occur
depending on the precise time at which the kettle was removed. Now, if
you are considering, strictly, a multi-processor distributed simulation then
you will probably have to rollback events (you might want to check out
the literature associated with the distributed simulation folks).
Paul Fishwick
Univ. of Florida
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Date: Fri, 9 Jun 89 09:18:50 -0400
From: Paul Fishwick <fishwick@fish.cis.ufl.edu>
To: simulation@ufl.edu
[[A recent talk given at the Universities of Arizona and Florida
--- any interested readers can contact the speaker directly at
hag@aipna.edinburgh.ac.uk (for reports, etc.) -PAF ]]
The EcoLogic System:
A Simulation System using Logic Programming
Ms. Mandy Haggith
Department of Computer Science
Edinburgh University
Scotland
ABSTRACT
Many ecologists wish to test out hypotheses about a particular
ecological system by constructing and manipulating a mathematical
model of that system. A convenient and powerful way of doing this is
to write and run a simulation program implementing the appropriate
mathematical model. Unfortunately many ecologists do not have, and do
not want to learn, the various programming techniques necessary to
construct simulation programs themselves. A valuable tool for such
ecologists, therefore, would be a computer system which would help
them to describe their ecological systems in ecological terminology,
and would use this information to construct appropriate simulation
programs. The aim of the ECO project is to build such a tool. A
prototype system meeting these requirements, called EcoLogic
(EL), has been constructed and is the subject of several ECO papers.
My talk will be an overview of current work on the ECO project,
motivated and illustrated by an example ecological model of the seal
populations in the North Sea, which are suffering a viral epidemic.
I shall outline how EL works, and indicate some of its major
weaknesses. These include its inability to cope with incomplete
ecological descriptions, problems with its user-interface,
and the limit to the range of ecological models which it can construct.
My research task is to correct these weaknesses, so the majority of the
talk will be a discussion of the solutions with which I am experimenting.
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Posted-Date: Fri, 16 Jun 89 10:31:12 CDT
Date: Fri, 16 Jun 89 10:31:12 CDT
From: vaughan%cadillac.cad.mcc.com@mcc.com (Paul Vaughan)
To: simulation@bikini.cis.ufl.edu
Subject: reversible simulation techniques?
I'm interested in reversible simulation, the ability to turn
back the clock, in the context of interactive discrete event
simulation. I need references or brief discussions of known
techniques, especially those that don't complicate the model writing
process.
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