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89 lines
2.5 KiB
89 lines
2.5 KiB
//==============================================================================
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//
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// Copyright (c) 2002-
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// Authors:
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// * Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford)
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// * Vincent Nimal <vincent.nimal@comlab.ox.ac.uk> (University of Oxford)
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//
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//------------------------------------------------------------------------------
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//
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// This file is part of PRISM.
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//
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// PRISM is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// PRISM is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with PRISM; if not, write to the Free Software Foundation,
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// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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//==============================================================================
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package simulator;
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import java.util.Date;
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import cern.jet.random.Exponential;
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import cern.jet.random.Uniform;
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import cern.jet.random.engine.MersenneTwister;
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/**
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* Random number generator for the simulator.
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* Currently, uses the Colt library.
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*/
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public class RandomNumberGenerator
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{
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private MersenneTwister random;
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private Uniform uniform;
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private Exponential exponential;
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/**
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* Create a new random number generator (seeded, by default, with the current time).
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*/
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public RandomNumberGenerator()
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{
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random = new MersenneTwister(new Date());
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uniform = new Uniform(random);
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// Create exponential generator (rate 1.0 but this is ignored from now on)
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exponential = new Exponential(1.0, random);
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}
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/**
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* Pick a (uniformly distributed) random integer in the range [0,...,n-1].
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*/
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public int randomUnifInt(int n)
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{
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return uniform.nextIntFromTo(0, n - 1);
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}
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/**
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* Pick a (uniformly distributed) random double in the range (0,1).
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*/
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public double randomUnifDouble()
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{
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return random.nextDouble();
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}
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/**
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* Pick a (uniformly distributed) random double in range (0,x).
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*/
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public double randomUnifDouble(double x)
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{
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return x * random.nextDouble();
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}
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/**
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* Pick a random double according to exponential distribution with rate x.
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*/
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public double randomExpDouble(double x)
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{
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return exponential.nextDouble(x);
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//return (-Math.log(random.nextDouble())) / x;
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}
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}
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