Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!uflorida!simulation From: simulation@uflorida.cis.ufl.edu (Moderator: Paul Fishwick) Newsgroups: comp.simulation Subject: SIMULATION DIGEST V14 N4 Message-ID: <22464@uflorida.cis.ufl.EDU> Date: 26 Feb 90 21:32:48 GMT Sender: fishwick@uflorida.cis.ufl.EDU Reply-To: simulation@uflorida.cis.ufl.edu Lines: 167 Approved: fishwick@uflorida.cis.ufl.edu Volume: 14, Issue: 4, Mon Feb 26 16:32:34 EST 1990 +----------------+ | TODAY'S TOPICS | +----------------+ (1) RE: High Level Design (2) TR: Time Warp Method (3) SmartModel on HP Workstations * 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 (128.227.224.1). Login as 'ftp', 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, 22 Feb 90 15:18 MST From: ROZENBLIT%EVAX2@Arizona.EDU Subject: IN reply to Wolfgang Mueller----High Level Design To: simulation@bikini.cis.ufl.EDU X-Envelope-To: simulation@bikini.cis.ufl.EDU X-Vms-To: IN::"simulation@bikini.cis.ufl.edu" SUMMARY OF RESEARCH IN KNOWLEDGE-BASED SYSTEM DESIGN AND SIMULATION Our research employs Artificial Intelligence and Multifacetted Simulation Modelling to unify engineering design activities and develop a methodology for systematic simulation model construction and evaluation. The methodology is based on codifying appropriate decompositions, taxonomic, and coupling relationships. This constitutes declarative design knowledge base. Beyond this, we provide the procedural knowledge base in the form of production rules used to process the elements in a design domain. As a step toward a complete knowledge representation scheme, we have combined the decomposition, taxonomic, and coupling relationships in a representation scheme called the system entity structure, a declarative scheme related to frame-theoretic and object-based representations. The entities of the entity structure refer to conceptual components of reality for which models may reside in the model base. Also associated with entities are slots for attribute knowledge representation. An entity may have several aspects, each denoting a decomposition, and therefore having several entities. An entity may also have several specializations, each representing a classification of the possible variants of the entity. The generative capability of the entity structure enables convenient generation and representation of model attributes at multiple levels of aggregation and abstraction. A primary application of the above knowledge representation scheme is the objectives-driven development of simulation models. In this approach, a model is synthesized from components identified through the system entity structure and stored in the model base. The synthesis process is guided by project's objectives, requirements, and constraints. The objectives guide a pruning process which reduces the entity structure to one or more composition trees from which models may be hierarchically built up from atomic components. Constraints, expressed in the form of production rules and placed on the aspects of the entity structure, restrict the family of possible pruned structures for more informed search. Performance of design models is evaluated through computer simulation in DEVS-Scheme environment. DEVS-Scheme is an object- oriented simulation environment for modeling and design that facilitates construction of families of models in a form easily reusable by retrieval from a model base. Models are evaluated in respective experimental frames. An experimental frame defines a set of input, control, output, and summary variables. Those objects specify conditions under which a model is simulated and observed. The environment supports construction of distributed, hierarchical discrete event models and is written in the PC-Scheme language which runs on IBM compatible microcomputers and AI Workstations. We have been validating the above methodology in case studies involving design and simulation of distributed computer architectures, local area networks, and more recently, VLSI packages. For more information, please contact: Jerzy W. Rozenblit or Bernard P. Zeigler Dept. of ECE, Bldg #4 University of Arizona Tucson, AZ 85721 rozenblit@arizevax.bitnet zeigler@arizevax.bitnet ------------------------------ Date: Fri, 23 Feb 90 17:59:41 -0800 From: liny@cs.washington.edu (Yi-Bing Lin) Return-Path: To: fishwick@bikini.cis.ufl.edu The following technical report can be requested via e-mail: liny@cs.washington.edu Reducing the State Saving Overhead For Time Warp Parallel Simulation Yi-Bing Lin and Edward D. Lazowska Department of Computer Science and Engineering University of Washington Seattle, WA 98195 Abstract The Time Warp mechanism is the most common ``optimistic'' parallel simulation protocol. A process executes every message as soon as it arrives. If a message with a smaller timestamp subsequently arrives, the process rolls back its state to the time of the earlier message and re-executes from that point. Clearly, the state of each process must be saved (checkpointed) regularly in case rollback is necessary. Although most existing Time Warp implementations checkpoint after every state transition, this is not necessary, and the checkpoint interval is in reality a tuning parameter of the simulation. In a previous paper, we derived the optimal frequency of checkpointing in Time Warp simulation based on a specific assumption concerning the rollback distance distribution. This paper derives distribution-free bounds for the state saving overhead. Using these bounds, we are able to select a checkpoint interval which minimizes the state saving overhead. High accuracy for our approach is shown in an experimental study. ------------------------------ Date: Thu, 22 Feb 90 16:32:29 EST From: mitel!spock!tsuia@uunet.UU.NET (Alan Tsui) To: uunet!bikini.cis.ufl.edu!simulation@uunet.UU.NET Subject: SmartModel I would like to know anyone has used SmartModel with System HILO (on HP workstation). How easy is it to use? Are they significant better than HILO models? Why? Thanks. Alan ------------------------------ END OF SIMULATION DIGEST ************************