package edu.princeton.cs.algs4.ch14;
import edu.princeton.cs.introcs.*;
/*************************************************************************
* Compilation: javac DoublingRatio.java
* Execution: java DoublingRatio
* Dependencies: ThreeSum.java Stopwatch.java StdRandom.java StdOut.java
*
*
* % java DoublingRatio
* 250 0.0 2.7
* 500 0.0 4.8
* 1000 0.1 6.9
* 2000 0.6 7.7
* 4000 4.5 8.0
* 8000 35.7 8.0
* ...
*
*************************************************************************/
/**
* The <tt>DoublingRatio</tt> class provides a client for measuring
* the running time of a method using a doubling ratio test.
* <p>
* For additional documentation, see <a href="http://algs4.cs.princeton.edu/14analysis">Section 1.4</a>
* of <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
*
* @author Robert Sedgewick
* @author Kevin Wayne
*/
public class DoublingRatio {
// This class should not be instantiated.
private DoublingRatio() { }
/**
* Returns the amount of time to call <tt>ThreeSum.count()</tt> with <em>N</em>
* random 6-digit integers.
* @param N the number of integers
* @return amount of time (in seconds) to call <tt>ThreeSum.count()</tt>
* with <em>N</em> random 6-digit integers
*/
public static double timeTrial(int N) {
int MAX = 1000000;
int[] a = new int[N];
for (int i = 0; i < N; i++) {
a[i] = StdRandom.uniform(-MAX, MAX);
}
Stopwatch timer = new Stopwatch();
ThreeSum.count(a);
return timer.elapsedTime();
}
/**
* Prints table of running times to call <tt>ThreeSum.count()</tt>
* for arrays of size 250, 500, 1000, 2000, and so forth, along
* with ratios of running times between successive array sizes.
*/
public static void main(String[] args) {
double prev = timeTrial(125);
for (int N = 250; true; N += N) {
double time = timeTrial(N);
StdOut.printf("%6d %7.1f %5.1f\n", N, time, time/prev);
prev = time;
}
}
}
/*************************************************************************
* Copyright 2002-2012, Robert Sedgewick and Kevin Wayne.
*
* This file is part of algs4-package.jar, which accompanies the textbook
*
* Algorithms, 4th edition by Robert Sedgewick and Kevin Wayne,
* Addison-Wesley Professional, 2011, ISBN 0-321-57351-X.
* http://algs4.cs.princeton.edu
*
*
* algs4-package.jar 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.
*
* algs4-package.jar 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.
* You should have received a copy of the GNU General Public License
* along with algs4-package.jar. If not, see http://www.gnu.org/licenses.
*************************************************************************/