simulation@ufl.edu (SIMULATION MODELING & ANALYSIS) (05/06/88)
Volume: 2, Issue: 2, Thu May 5 13:18:41 EDT 1988 +----------------+ | TODAY'S TOPICS | +----------------+ (1) Simulation with Combinatoric Problems (2) Economic Modeling (3) IMACS World Congress ---------------------------------------------------------------------------- To: comp-simulation@uunet.uu.net Path: pur-ee!gapp From: uiucdcs!pur-ee!gapp@uunet.uu.net (GAPP Research) Newsgroups: comp.simulation Subject: simulation of Combinatorics problem Date: 2 May 88 21:35:13 GMT Reply-To: uiucdcs!pur-ee!gapp@uunet.uu.net (GAPP Research) Distribution: usa Organization: Purdue University Engineering Computer Network Hi, dear netters: I have a problem in simulation and need some help from the netters. Here is what it looks like. Suppose I have a mesh grid of colored squares, say there are N=nxn of them. Suppose I also know that K of them are BLUE and N-K of them are RED. Let the coordination of these squares be denoted by (x,y) where 1 <= x <= n and 1 <= y <= n. We define the distance of two squares (i1, j2) and (i2, j2) by d=abs(i1-i2) + abs(j1-j2), i.e., the Manhattan distance between them. Given a pattern of how these K BLUEs are scattered among the RED squares, the distance of this pattern would be the maximal distance between two BLUE squares. What I'd like to find is the expected distance of the patterns with the uniform distribution P(K, N), which means there are K BLUEs in the N (nxn) square grids. The most intuitive way for me is to write a program that generate a pattern first, counts the distance of two farest squares, sums there distances together, and average it by dividing with the number of possible distribution patterns. What hit me bad here is the number of patterns would be C(N,K) which is a combinatoric value. It is just infeasible to write a program actually that generate all there patterns, counts the max distance of that pattern, and then find the expected distance as the result. If I do it this way, all computer users here would kill me for sure. Is there any good ( or tricky ) statistical way that allows me to run this simulation instead? I asked a couple of friends here, but this sort of combinatorics problem just keep them far away from me. Thanks a lot in advance for the help. --aynang@ed.ecn.purdue.edu aynang%ed@ecn.purdue.edu pur-ee\!ed\!aynang PS. Please mail to my e-mail address if possible. I am using a lab account to post this news. ---------------------------------------------------------------------------- Return-Path: <jon@june> To: comp-simulation@beaver.cs.washington.edu Path: uw-june!jon From: jon@june.cs.washington.edu (Jon Jacky) Newsgroups: comp.simulation Subject: Economic modelling Keywords: simulation, modelling, economics, world bank Date: 3 May 88 15:52:38 GMT Organization: U of Washington, Computer Science, Seattle The April 1, 1988 issue of DATAMATION includes an article, "Economic Modeling Gains Despite Accuracy Concerns," by Gary McWilliams (pps. 43-54). I am not familiar with this field, and the article never really explains what the inputs and outputs of the models are, where they come from or how they are validated. Nevertheless, people apparently use them to forecast economic trends and seem to regard them as useful. One model, called Project Link, includes more than 20,000 equations. Much of the article appears to be based on an interview with Sam Cole, economist and model builder at SUNY Buffalo, and author of GLOBAL MODELS AND THE INTERNATIONAL ECONOMIC ORDER (Oxford Pergamon, 1977). The article reports, "The World Bank uses a global model in its lending, says Cole, sometimes to the detriment of its debtors. 'When the World Bank lends [a country] money, it expects that country to have a [repayment] plan, and usually pursuades the country to accept World Bank forecasts. Since its forecasts are usually wrong, these countries end up with debts and no way to repay them,' says Cole. The World Bank's use of optimistic growth forecasts often are built into the models for political reasons, according to Cole." - Jon Jacky, University of Washington ---------------------------------------------------------------------------- Date: Tue, 3 May 88 17:09:35 EDT From: vichneve@aramis.rutgers.edu (Robert Vichnevetsky) To: fishwick@fish.cis.ufl.edu, Vichneve@aramis.rutgers.edu Subject: IMACS World Congress Please insert the following in your Digest / Thanks in anticipation ****************************************************************************** ========================= * 12th IMACS WORLD CONGRESS * * ON SCIENTIFIC COMPUTATION * ========================= July 18-22, 1988 - Paris, France ================================ The 12th. IMACS World Congress will take place at the historic site of the Sorbonne/Lycee Louis le Grand in the Quartier Latin, a central area of Paris known since the Middle Ages for its prestigious Schools and its University. The program of the Congress features some 900 papers, to be presented by authors from almost every country in the world. The topics cover a wide range of interests, including Computational Mathematics, Numerical Analysis, Modelling of Systems, AI and Expert systems, Computational Physics, Computational Acoustics, Applications in Science and Engineering, and Hardware and Software for Scientific Computation. Registration forms, and the preliminary program, which contains a listing of all papers and social events, may be obtained by writing to: IMACS Secretariat Attn: K. Hahn Rutgers University Dept. of Computer Science New Brunswick, NJ 08903 USA Tel: 201-932-3998 ARPANET: khahn@aramis.rutgers.edu or to : IMACS Congress Secretariat I.D.N. BP 48 F 59651 Villeneuve d' Ascq . Cedex France Phone (33) 20 91 01 15 ************************************************************** +--------------------------+ | END OF SIMULATION DIGEST | +--------------------------+