/*
* 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 opennlp.tools.ngram;
import java.util.Collection;
import java.util.LinkedList;
import org.junit.Assert;
import org.junit.Test;
import opennlp.tools.util.StringList;
/**
* Tests for {@link NGramUtils}
*/
public class NGramUtilsTest {
@Test
public void testBigramMLProbability() {
Collection<StringList> set = new LinkedList<>();
set.add(new StringList("<s>", "I", "am", "Sam", "</s>"));
set.add(new StringList("<s>", "Sam", "I", "am", "</s>"));
set.add(new StringList("<s>", "I", "do", "not", "like", "green", "eggs", "and", "ham", "</s>"));
set.add(new StringList(""));
Double d = NGramUtils.calculateBigramMLProbability("<s>", "I", set);
Assert.assertEquals(Double.valueOf(0.6666666666666666d), d);
d = NGramUtils.calculateBigramMLProbability("Sam", "</s>", set);
Assert.assertEquals(Double.valueOf(0.5d), d);
d = NGramUtils.calculateBigramMLProbability("<s>", "Sam", set);
Assert.assertEquals(Double.valueOf(0.3333333333333333d), d);
}
@Test
public void testTrigramMLProbability() {
Collection<StringList> set = new LinkedList<>();
set.add(new StringList("<s>", "I", "am", "Sam", "</s>"));
set.add(new StringList("<s>", "Sam", "I", "am", "</s>"));
set.add(new StringList("<s>", "I", "do", "not", "like", "green", "eggs", "and", "ham", "</s>"));
set.add(new StringList(""));
Double d = NGramUtils.calculateTrigramMLProbability("I", "am", "Sam", set);
Assert.assertEquals(Double.valueOf(0.5), d);
d = NGramUtils.calculateTrigramMLProbability("Sam", "I", "am", set);
Assert.assertEquals(Double.valueOf(1d), d);
}
@Test
public void testNgramMLProbability() {
Collection<StringList> set = new LinkedList<>();
set.add(new StringList("<s>", "I", "am", "Sam", "</s>"));
set.add(new StringList("<s>", "Sam", "I", "am", "</s>"));
set.add(new StringList("<s>", "I", "do", "not", "like", "green", "eggs", "and", "ham", "</s>"));
set.add(new StringList(""));
Double d = NGramUtils.calculateNgramMLProbability(new StringList("I", "am", "Sam"), set);
Assert.assertEquals(Double.valueOf(0.5), d);
d = NGramUtils.calculateNgramMLProbability(new StringList("Sam", "I", "am"), set);
Assert.assertEquals(Double.valueOf(1d), d);
}
@Test
public void testLinearInterpolation() throws Exception {
Collection<StringList> set = new LinkedList<>();
set.add(new StringList("the", "green", "book", "STOP"));
set.add(new StringList("my", "blue", "book", "STOP"));
set.add(new StringList("his", "green", "house", "STOP"));
set.add(new StringList("book", "STOP"));
Double lambda = 1d / 3d;
Double d = NGramUtils.calculateTrigramLinearInterpolationProbability("the", "green",
"book", set, lambda, lambda, lambda);
Assert.assertNotNull(d);
Assert.assertEquals("wrong result", Double.valueOf(0.5714285714285714d), d);
}
@Test
public void testLinearInterpolation2() throws Exception {
Collection<StringList> set = new LinkedList<>();
set.add(new StringList("D", "N", "V", "STOP"));
set.add(new StringList("D", "N", "V", "STOP"));
Double lambda = 1d / 3d;
Double d = NGramUtils.calculateTrigramLinearInterpolationProbability("N", "V",
"STOP", set, lambda, lambda, lambda);
Assert.assertNotNull(d);
Assert.assertEquals("wrong result", Double.valueOf(0.75d), d);
}
@Test
public void testGetNGrams() throws Exception {
Collection<StringList> nGrams = NGramUtils.getNGrams(new StringList("I",
"saw", "brown", "fox"), 2);
Assert.assertEquals(3, nGrams.size());
nGrams = NGramUtils.getNGrams(new StringList("I", "saw", "brown", "fox"), 3);
Assert.assertEquals(2, nGrams.size());
}
}