svn commit: r1373777 - in /commons/proper/math/trunk/src: main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java

[lu...@apache.org]

Author: luc
Date: Thu Aug 16 10:06:50 2012
New Revision: 1373777

URL: http://svn.apache.org/viewvc?rev=1373777&view=rev
Log:
Added copySign to DerivativeStructure.

Modified:
    commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java
    commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java

Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java?rev=1373777&r1=1373776&r2=1373777&view=diff
==============================================================================
--- commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java (original)
+++ commons/proper/math/trunk/src/main/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructure.java Thu Aug 16 10:06:50 2012
@@ -386,6 +386,22 @@ public class DerivativeStructure impleme
                                        FastMath.floor(data[0]));
     }
 
+    /**
+     * Returns the instance with the sign of the argument.
+     * A NaN {@code sign} argument is treated as positive.
+     *
+     * @param sign the sign for the returned value
+     * @return the instance with the same sign as the {@code sign} argument
+     */
+    public DerivativeStructure copySign(final double sign){
+        long m = Double.doubleToLongBits(data[0]);
+        long s = Double.doubleToLongBits(sign);
+        if ((m >= 0 && s >= 0) || (m < 0 && s < 0)) { // Sign is currently OK
+            return this;
+        }
+        return negate(); // flip sign
+    }
+
     /** {@inheritDoc} */
     public DerivativeStructure reciprocal() {
         final DerivativeStructure result = new DerivativeStructure(compiler);

Modified: commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java
URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java?rev=1373777&r1=1373776&r2=1373777&view=diff
==============================================================================
--- commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java (original)
+++ commons/proper/math/trunk/src/test/java/org/apache/commons/math3/analysis/differentiation/DerivativeStructureTest.java Thu Aug 16 10:06:50 2012
@@ -766,6 +766,21 @@ public class DerivativeStructureTest {
     }
 
     @Test
+    public void testCopySign() {
+        DerivativeStructure minusOne = new DerivativeStructure(1, 1, 0, -1.0);
+        Assert.assertEquals(+1.0, minusOne.copySign(+1.0).getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(-1.0, minusOne.copySign(+1.0).getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(-1.0, minusOne.copySign(-1.0).getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(+1.0, minusOne.copySign(-1.0).getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(+1.0, minusOne.copySign(+0.0).getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(-1.0, minusOne.copySign(+0.0).getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(-1.0, minusOne.copySign(-0.0).getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(+1.0, minusOne.copySign(-0.0).getPartialDerivative(1), 1.0e-15);
+        Assert.assertEquals(+1.0, minusOne.copySign(Double.NaN).getPartialDerivative(0), 1.0e-15);
+        Assert.assertEquals(-1.0, minusOne.copySign(Double.NaN).getPartialDerivative(1), 1.0e-15);
+    }
+
+    @Test
     public void testField() {
         for (int maxOrder = 1; maxOrder < 5; ++maxOrder) {
             DerivativeStructure x = new DerivativeStructure(3, maxOrder, 0, 1.0);