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Date: Sat, 9 Jun 2012 13:06:42 +0000 (UTC)
From: =?utf-8?Q?S=C3=A9bastien_Brisard_=28JIRA=29?= <jira@apache.org>
To: issues@commons.apache.org
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Subject: [jira] [Created] (MATH-802) RealVector.subtract(RealVector) returns
 wrong answer.
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S=C3=A9bastien Brisard created MATH-802:
--------------------------------------

             Summary: RealVector.subtract(RealVector) returns wrong answer.
                 Key: MATH-802
                 URL: https://issues.apache.org/jira/browse/MATH-802
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 3.0
            Reporter: S=C3=A9bastien Brisard
            Assignee: S=C3=A9bastien Brisard
             Fix For: 3.1


The following piece of code
{code:java}
import org.apache.commons.math3.linear.ArrayRealVector;
import org.apache.commons.math3.linear.OpenMapRealVector;
import org.apache.commons.math3.linear.RealVectorFormat;

public class DemoMath {

    public static void main(String[] args) {
        final double[] data1 =3D {
            0d, 1d, 0d, 0d, 2d
        };
        final double[] data2 =3D {
            3d, 0d, 4d, 0d, 5d
        };
        final RealVectorFormat format =3D new RealVectorFormat();
        System.out.println(format.format(new ArrayRealVector(data1)
            .subtract(new ArrayRealVector(data2))));
        System.out.println(format.format(new OpenMapRealVector(data1)
            .subtract(new ArrayRealVector(data2))));
    }
}
{code}

prints
{noformat}
{-3; 1; -4; 0; -3}
{3; 1; 4; 0; -3}
{noformat}

the second line being wrong. In fact, when subtracting mixed types, {{OpenM=
apRealVector}} delegates to the default implementation in {{RealVector}} wh=
ich is buggy.

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