org.apache.mahout.df.builder.DefaultTreeBuilderTest.java Source code

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Here is the source code for org.apache.mahout.df.builder.DefaultTreeBuilderTest.java

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/**
 * 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.df.builder;

import java.util.Random;
import java.util.Arrays;

import org.apache.commons.lang.ArrayUtils;
import org.apache.mahout.common.MahoutTestCase;
import org.apache.mahout.common.RandomUtils;

public class DefaultTreeBuilderTest extends MahoutTestCase {

    /**
     * make sure that DefaultTreeBuilder.randomAttributes() returns the correct number of attributes, that have not been
     * selected yet
     *
     * @throws Exception
     */
    public void testRandomAttributes() throws Exception {
        Random rng = RandomUtils.getRandom();
        int nbAttributes = rng.nextInt(100) + 1;
        boolean[] selected = new boolean[nbAttributes];

        for (int nloop = 0; nloop < 100; nloop++) {
            Arrays.fill(selected, false);

            // randomly select some attributes
            int nbSelected = rng.nextInt(nbAttributes - 1);
            for (int index = 0; index < nbSelected; index++) {
                int attr;
                do {
                    attr = rng.nextInt(nbAttributes);
                } while (selected[attr]);

                selected[attr] = true;
            }

            int m = rng.nextInt(nbAttributes);

            int[] attrs = DefaultTreeBuilder.randomAttributes(rng, selected, m);

            assertEquals(Math.min(m, nbAttributes - nbSelected), attrs.length);

            for (int attr : attrs) {
                // the attribute should not be already selected
                assertFalse("an attribute has already been selected", selected[attr]);

                // each attribute should be in the range [0, nbAttributes[
                assertTrue(attr >= 0);
                assertTrue(attr < nbAttributes);

                // each attribute should appear only once
                assertEquals(ArrayUtils.indexOf(attrs, attr), ArrayUtils.lastIndexOf(attrs, attr));
            }
        }
    }
}