CauchySchwartz.java


Below is the syntax highlighted version of CauchySchwartz.java from §9.1 Scientific Computation.



/******************************************************************************
 *  Compilation:  javac CauchySchwartz.java
 *  Execution:    java CauchySchwartz x y
 *  
 *  Tests whether the special case of the Cauchy-Schwartz identity
 *  is true for x and y.
 *  
 *       2 * (x*x + y*y) >= (x + y) * (x + y)
 *  or
 *       (x*x + y*y) >= 2 * (x * y)
 *
 *  Surprisingly, it is not always true with floating point numbers!
 *
 *  % java CauchySchwartz 2.5 3.0
 *  true
 *  true
 *
 *  % java CauchySchwartz 0.5 0.51
 *  true
 *  true
 *
 *  % java CauchySchwartz 0.5 0.5
 *  true
 *  true
 *
 *  % java CauchySchwartz 0.5000000000000002 0.5000000000000001
 *  false
 *  true

 *  % java CauchySchwartz 0.21  0.2100000000000001
 *  false
 *  false
 *  
 *  % java CauchySchwartz 0.92 0.9200000000000002
 *  false
 *  true
 *
 *  % java CauchySchwartz 0.9200000000000002 .92
 *  false
 *  true
 *
 ******************************************************************************/

public class CauchySchwartz {

    public static void main(String[] args) { 
        double x = Double.parseDouble(args[0]);
        double y = Double.parseDouble(args[1]);

        StdOut.println(x);
        StdOut.println(y);

        double a = 2 * (x*x + y*y);
        double b = (x + y) * (x + y);
        StdOut.println(a >= b);

        double c = x*x + y*y;
        double d = 2 * (x * y);
        StdOut.println(c >= d);
   }

}


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Last updated: Fri Oct 20 14:12:12 EDT 2017.