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Added test case to ensure permuting arrays changes hash. 

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/math/branches/MATH_2_0@719995 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2008-11-23 15:35:11 +00:00
parent 9b8d0da71a
commit 54a42c0024
1 changed files with 30 additions and 0 deletions
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30
src/test/org/apache/commons/math/util/MathUtilsTest.java
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@ -19,6 +19,7 @@ import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
import org.apache.commons.math.random.RandomDataImpl;
import org.apache.commons.math.TestUtils;
/**
@ -331,6 +332,35 @@ public final class MathUtilsTest extends TestCase {
assertFalse(MathUtils.hash(new double[] { 1d }) ==
MathUtils.hash(new double[] { 1d, 1d }));
}
/**
* Make sure that permuted arrays do not hash to the same value.
*/
public void testPermutedArrayHash() {
double[] original = new double[10];
double[] permuted = new double[10];
RandomDataImpl random = new RandomDataImpl();
// Generate 10 distinct random values
for (int i = 0; i < 10; i++) {
original[i] = random.nextUniform((double)i + 0.5, (double)i + 0.75);
}
// Generate a random permutation, making sure it is not the identity
boolean isIdentity = true;
do {
int[] permutation = random.nextPermutation(10, 10);
for (int i = 0; i < 10; i++) {
if (i != permutation[i]) {
isIdentity = false;
}
permuted[i] = original[permutation[i]];
}
} while (isIdentity);
// Verify that permuted array has different hash
assertFalse(MathUtils.hash(original) == MathUtils.hash(permuted));
}
public void testIndicatorByte() {
assertEquals((byte)1, MathUtils.indicator((byte)2));