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MATH-1020. 

Fixed "nextPermutation" in "RandomDataGenerator". Bug showed up when using
a fixed version of "shuffle" (MATH-1019) added in "MathArrays" (MATH-1010).
Added overloaded "shuffle" method (used in the above fix).


git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/trunk@1512306 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Gilles Sadowski 2013-08-09 13:55:49 +00:00
parent c8fc11146f
commit 6d0394d27d
2 changed files with 24 additions and 6 deletions
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10
src/main/java/org/apache/commons/math3/random/RandomDataGenerator.java
View File

@ -46,6 +46,7 @@ import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.apache.commons.math3.exception.NumberIsTooLargeException;
import org.apache.commons.math3.exception.OutOfRangeException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.util.MathArrays;
/**
* Implements the {@link RandomData} interface using a {@link RandomGenerator}
@ -639,13 +640,10 @@ public class RandomDataGenerator implements RandomData, Serializable {
}
int[] index = getNatural(n);
shuffle(index, n - k);
int[] result = new int[k];
for (int i = 0; i < k; i++) {
result[i] = index[n - i - 1];
}
MathArrays.shuffle(index, getRandomGenerator());
return result;
// Return a new array containing the first "k" entries of "index".
return MathArrays.copyOf(index, k);
}
/**

20
src/main/java/org/apache/commons/math3/util/MathArrays.java
View File

@ -1505,4 +1505,24 @@ public class MathArrays {
throw new MathInternalError(); // Should never happen.
}
}
/**
* Shuffle the entries of the given array.
*
* @param list Array whose entries will be shuffled (in-place).
* @param rng Random number generator.
*/
public static void shuffle(int[] list,
RandomGenerator rng) {
shuffle(list, 0, Position.TAIL, rng);
}
/**
* Shuffle the entries of the given array.
*
* @param list Array whose entries will be shuffled (in-place).
*/
public static void shuffle(int[] list) {
shuffle(list, new Well19937c());
}
}