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//******************************************************************************
//
// File: GenData.java
// Package: edu.rit.mri.test
// Unit: Class edu.rit.mri.test.GenData
//
// This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.mri.test;
import edu.rit.numeric.NormalPrng;
import edu.rit.util.Random;
/**
* Class GenData is a main program that generates a spin signal data set.
* <P>
* Usage: java edu.rit.mri.test.GenData <I>seed</I> <I>stdev</I> <I>tmax</I>
* <I>nt</I> <I>ρ</I><SUB>1</SUB> <I>x</I><SUB>1</SUB> [
* <I>ρ</I><SUB>2</SUB> <I>x</I><SUB>2</SUB> . . . ]
* <P>
* The program:
* <OL TYPE=1>
* <LI>
* Initializes a pseudorandom number generator with <I>seed</I>.
* <LI>
* Generates <I>nt</I> values of <I>t</I>, unevenly spaced, up to <I>tmax</I>.
* <LI>
* For each value of <I>t</I>, computes the spin signal
* <CENTER>
* <I>S</I>(<I>t</I>) = Σ<SUB><I>i</I></SUB> <I>ρ</I><SUB><I>i</I></SUB> [1 − 2 exp(−<I>x</I><SUB><I>i</I></SUB> <I>t</I>)]
* </CENTER>
* where <I>ρ</I><SUB><I>i</I></SUB> is the <I>i</I>-th spin density and
* <I>x</I><SUB><I>i</I></SUB> is the <I>i</I>-th spin relaxation rate.
* <LI>
* For each spin signal value, adds random Gaussian noise with mean 0 and
* standard deviation <I>stdev</I>.
* <LI>
* Prints each value of <I>t</I> and the corresponding <I>S</I>(<I>t</I>) with
* noise on one line of the standard output.
* </OL>
*
* @author Alan Kaminsky
* @version 10-Jun-2008
*/
public class GenData
{
// Prevent construction.
private GenData()
{
}
// Main program.
/**
* Main program.
*/
public static void main
(String[] args)
throws Exception
{
// Parse command line arguments.
if (args.length < 6 || (args.length % 2) != 0) usage();
long seed = Long.parseLong (args[0]);
double stdev = Double.parseDouble (args[1]);
double tmax = Double.parseDouble (args[2]);
int nt = Integer.parseInt (args[3]);
int ns = (args.length - 4)/2;
double[] rho = new double [ns];
double[] x = new double [ns];
for (int i = 0; i < ns; ++ i)
{
rho[i] = Double.parseDouble (args[2*i+4]);
x[i] = Double.parseDouble (args[2*i+5]);
}
// Set up Gaussian PRNG.
NormalPrng prng =
new NormalPrng (Random.getInstance (seed), 0.0, stdev);
// Generate and print data.
for (int i = 1; i <= nt; ++ i)
{
//double t = Math.pow (tmax, ((double) i)/((double) nt));
double t = Math.pow (((double) i)/((double) nt), 2.4) * tmax;
double s = 0.0;
for (int j = 0; j < ns; ++ j)
{
s += rho[j]*(1.0 - 2.0*Math.exp(-x[j]*t));
}
s += prng.next();
System.out.print (t);
System.out.print ('\t');
System.out.print (s);
System.out.println();
}
}
// Hidden operations.
/**
* Print a usage message and exit.
*/
private static void usage()
{
System.err.println ("Usage: java edu.rit.mri.test.GenData <seed> <stdev> <tmax> <nt> <rho1> <x1> [<rho2> <x2> ...]");
System.err.println ("<seed> = Random seed");
System.err.println ("<stdev> = Measurement error standard deviation");
System.err.println ("<tmax> = Largest t value");
System.err.println ("<nt> = Number of t values");
System.err.println ("<rho1> = Spin density");
System.err.println ("<x1> = Spin relaxation rate");
System.exit (1);
}
}
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