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[MATH-996] Fix creation of Fraction/BigFraction objects in maxDenominator mode when the value is close to an actual fraction. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1519204 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Thomas Neidhart 2013-08-31 19:43:02 +00:00
parent d7fd760eb8
commit 86545dab3e
6 changed files with 33 additions and 4 deletions
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3
pom.xml
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@ -132,6 +132,9 @@
<contributor> <contributor>
<name>Eldar Agalarov</name> <name>Eldar Agalarov</name>
</contributor> </contributor>
<contributor>
<name>Tim Allison</name>
</contributor>
<contributor> <contributor>
<name>C. Scott Ananian</name> <name>C. Scott Ananian</name>
</contributor> </contributor>

5
src/changes/changes.xml
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@ -51,6 +51,11 @@ If the output is not quite correct, check for invisible trailing spaces!
</properties> </properties>
<body> <body>
<release version="x.y" date="TBD" description="TBD"> <release version="x.y" date="TBD" description="TBD">
<action dev="tn" type=fix issue="MATH-996" due-to="Tim Allison">
Creating a "Fraction" or "BigFraction" object with a maxDenominator parameter
does not throw a "FractionConversionException" in case the value is very close
to fraction.
</action>
<action dev="tn" type="add" issue="MATH-1028" due-to="Thorsten Schäfer"> <action dev="tn" type="add" issue="MATH-1028" due-to="Thorsten Schäfer">
Added new distance metric "EarthMoversDistance". Added new distance metric "EarthMoversDistance".
</action> </action>

5
src/main/java/org/apache/commons/math3/fraction/BigFraction.java
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@ -301,6 +301,11 @@ public class BigFraction
p2 = (a1 * p1) + p0; p2 = (a1 * p1) + p0;
q2 = (a1 * q1) + q0; q2 = (a1 * q1) + q0;
if ((p2 > overflow) || (q2 > overflow)) { if ((p2 > overflow) || (q2 > overflow)) {
// in maxDenominator mode, if the last fraction was very close to the actual value
// q2 may overflow in the next iteration; in this case return the last one.
if (epsilon == 0.0 && FastMath.abs(q1) < maxDenominator) {
break;
}
throw new FractionConversionException(value, p2, q2); throw new FractionConversionException(value, p2, q2);
} }

14
src/main/java/org/apache/commons/math3/fraction/Fraction.java
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@ -83,6 +83,9 @@ public class Fraction
/** Serializable version identifier */ /** Serializable version identifier */
private static final long serialVersionUID = 3698073679419233275L; private static final long serialVersionUID = 3698073679419233275L;
/** The default epsilon used for convergence. */
private static final double DEFAULT_EPSILON = 1e-5;
/** The denominator. */ /** The denominator. */
private final int denominator; private final int denominator;
@ -96,7 +99,7 @@ public class Fraction
* converge. * converge.
*/ */
public Fraction(double value) throws FractionConversionException { public Fraction(double value) throws FractionConversionException {
this(value, 1.0e-5, 100); this(value, DEFAULT_EPSILON, 100);
} }
/** /**
@ -182,8 +185,7 @@ public class Fraction
throw new FractionConversionException(value, a0, 1l); throw new FractionConversionException(value, a0, 1l);
} }
// check for (almost) integer arguments, which should not go // check for (almost) integer arguments, which should not go to iterations.
// to iterations.
if (FastMath.abs(a0 - value) < epsilon) { if (FastMath.abs(a0 - value) < epsilon) {
this.numerator = (int) a0; this.numerator = (int) a0;
this.denominator = 1; this.denominator = 1;
@ -206,7 +208,13 @@ public class Fraction
long a1 = (long)FastMath.floor(r1); long a1 = (long)FastMath.floor(r1);
p2 = (a1 * p1) + p0; p2 = (a1 * p1) + p0;
q2 = (a1 * q1) + q0; q2 = (a1 * q1) + q0;
if ((FastMath.abs(p2) > overflow) || (FastMath.abs(q2) > overflow)) { if ((FastMath.abs(p2) > overflow) || (FastMath.abs(q2) > overflow)) {
// in maxDenominator mode, if the last fraction was very close to the actual value
// q2 may overflow in the next iteration; in this case return the last one.
if (epsilon == 0.0 && FastMath.abs(q1) < maxDenominator) {
break;
}
throw new FractionConversionException(value, p2, q2); throw new FractionConversionException(value, p2, q2);
} }

3
src/test/java/org/apache/commons/math3/fraction/BigFractionTest.java
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@ -154,6 +154,9 @@ public class BigFractionTest {
assertFraction(8, 13, new BigFraction(0.6152, 99)); assertFraction(8, 13, new BigFraction(0.6152, 99));
assertFraction(510, 829, new BigFraction(0.6152, 999)); assertFraction(510, 829, new BigFraction(0.6152, 999));
assertFraction(769, 1250, new BigFraction(0.6152, 9999)); assertFraction(769, 1250, new BigFraction(0.6152, 9999));
// MATH-996
assertFraction(1, 2, new BigFraction(0.5000000001, 10));
} }
@Test @Test

7
src/test/java/org/apache/commons/math3/fraction/FractionTest.java
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@ -129,6 +129,9 @@ public class FractionTest {
assertFraction(8, 13, new Fraction(0.6152, 99)); assertFraction(8, 13, new Fraction(0.6152, 99));
assertFraction(510, 829, new Fraction(0.6152, 999)); assertFraction(510, 829, new Fraction(0.6152, 999));
assertFraction(769, 1250, new Fraction(0.6152, 9999)); assertFraction(769, 1250, new Fraction(0.6152, 9999));
// MATH-996
assertFraction(1, 2, new Fraction(0.5000000001, 10));
} }
@Test @Test
@ -141,7 +144,9 @@ public class FractionTest {
private void checkIntegerOverflow(double a) { private void checkIntegerOverflow(double a) {
try { try {
new Fraction(a, 1.0e-12, 1000); @SuppressWarnings("unused")
Fraction f = new Fraction(a, 1.0e-12, 1000);
//System.out.println(f.getNumerator() + "/" + f.getDenominator());
Assert.fail("an exception should have been thrown"); Assert.fail("an exception should have been thrown");
} catch (ConvergenceException ce) { } catch (ConvergenceException ce) {
// expected behavior // expected behavior