Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!sun-barr!cs.utexas.edu!tut.cis.ohio-state.edu!ukma!uflorida!simulation From: simulation@uflorida.cis.ufl.edu (Moderator: Paul Fishwick) Newsgroups: comp.simulation Subject: SIMULATION DIGEST V9 N5 Message-ID: <20477@uflorida.cis.ufl.EDU> Date: 16 Jun 89 15:55:36 GMT Sender: fishwick@uflorida.cis.ufl.EDU Reply-To: simulation@uflorida.cis.ufl.edu Lines: 123 Approved: fishwick@uflorida.cis.ufl.edu Volume: 9, Issue: 5, Fri Jun 16 11:54:31 EDT 1989 +----------------+ | TODAY'S TOPICS | +----------------+ (1) Re: Event Unscheduling (2) The EcoLogic System (3) Reversable Simulation * Moderator: Paul Fishwick, Univ. of Florida * Send topical mail to: simulation@uflorida.cis.ufl.edu * 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. ----------------------------------------------------------------------------- Date: Thu, 8 Jun 89 09:42:30 -0400 From: Paul Fishwick 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 ------------------------------ Date: Fri, 9 Jun 89 09:18:50 -0400 From: Paul Fishwick 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. ------------------------------ 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. ------------------------------ END OF SIMULATION DIGEST ************************