/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.common.distance;
import junit.framework.TestCase;
import org.apache.mahout.matrix.DenseVector;
import org.apache.mahout.matrix.SparseVector;
import org.apache.mahout.matrix.Vector;
public abstract class DefaultDistanceMeasureTest extends TestCase {
public abstract DistanceMeasure distanceMeasureFactory();
public void testMeasure() {
DistanceMeasure distanceMeasure = distanceMeasureFactory();
Vector[] vectors = {
new DenseVector(new double[]{1, 1, 1, 1, 1, 1}),
new DenseVector(new double[]{2, 2, 2, 2, 2, 2}),
new DenseVector(new double[]{6, 6, 6, 6, 6, 6}),
new DenseVector(new double[]{-1,-1,-1,-1,-1,-1})
};
compare(distanceMeasure, vectors);
vectors = new Vector[4];
vectors[0] = new SparseVector(5);
vectors[0].setQuick(0, 1);
vectors[0].setQuick(3, 1);
vectors[0].setQuick(4, 1);
vectors[1] = new SparseVector(5);
vectors[1].setQuick(0, 2);
vectors[1].setQuick(3, 2);
vectors[1].setQuick(4, 2);
vectors[2] = new SparseVector(5);
vectors[2].setQuick(0, 6);
vectors[2].setQuick(3, 6);
vectors[2].setQuick(4, 6);
vectors[3] = new SparseVector(5);
compare(distanceMeasure, vectors);
}
private static void compare(DistanceMeasure distanceMeasure, Vector[] vectors) {
double[][] distanceMatrix = new double[4][4];
for (int a = 0; a < 4; a++) {
for (int b = 0; b < 4; b++) {
distanceMatrix[a][b] = distanceMeasure.distance(vectors[a], vectors[b]);
}
}
assertEquals("Distance from first vector to itself is not zero", 0.0, distanceMatrix[0][0]);
assertTrue(distanceMatrix[0][0] < distanceMatrix[0][1]);
assertTrue(distanceMatrix[0][1] < distanceMatrix[0][2]);
assertEquals("Distance from second vector to itself is not zero", 0.0, distanceMatrix[1][1]);
assertTrue(distanceMatrix[1][0] > distanceMatrix[1][1]);
assertTrue(distanceMatrix[1][2] > distanceMatrix[1][0]);
assertEquals("Distance from third vector to itself is not zero", 0.0, distanceMatrix[2][2]);
assertTrue(distanceMatrix[2][0] > distanceMatrix[2][1]);
assertTrue(distanceMatrix[2][1] > distanceMatrix[2][2]);
for (int a = 0; a < 4; a++) {
for (int b = 0; b < 4; b++) {
assertTrue("Distance between vectors less than zero: "
+ distanceMatrix[a][b] + " = " + distanceMeasure.toString() +
".distance("+ vectors[a].asFormatString() + ", "
+ vectors[b].asFormatString() + ')',
distanceMatrix[a][b] >= 0);
if(vectors[a].plus(vectors[b]).norm(2) == 0 && vectors[a].norm(2) > 0) {
assertTrue("Distance from v to -v is equal to zero"
+ vectors[a].asFormatString() + " = -" + vectors[b].asFormatString(),
distanceMatrix[a][b] > 0);
}
}
}
}
}