/*
* 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 hivemall.knn.similarity;
import hivemall.utils.hadoop.HiveUtils;
import java.util.Arrays;
import java.util.List;
import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.UDFType;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.objectinspector.ListObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.io.FloatWritable;
/**
* @see http://en.wikipedia.org/wiki/Cosine_similarity#Angular_similarity
*/
@Description(name = "angular_similarity",
value = "_FUNC_(ftvec1, ftvec2) - Returns an angular similarity of the given two vectors")
@UDFType(deterministic = true, stateful = false)
public final class AngularSimilarityUDF extends GenericUDF {
private ListObjectInspector arg0ListOI, arg1ListOI;
@Override
public ObjectInspector initialize(ObjectInspector[] argOIs) throws UDFArgumentException {
if (argOIs.length != 2) {
throw new UDFArgumentException("angular_similarity takes 2 arguments");
}
this.arg0ListOI = HiveUtils.asListOI(argOIs[0]);
this.arg1ListOI = HiveUtils.asListOI(argOIs[1]);
return PrimitiveObjectInspectorFactory.writableFloatObjectInspector;
}
@Override
public FloatWritable evaluate(DeferredObject[] arguments) throws HiveException {
List<String> ftvec1 = HiveUtils.asStringList(arguments[0], arg0ListOI);
List<String> ftvec2 = HiveUtils.asStringList(arguments[1], arg1ListOI);
float similarity = angularSimilarity(ftvec1, ftvec2);
return new FloatWritable(similarity);
}
public static float angularSimilarity(final List<String> ftvec1, final List<String> ftvec2) {
float cosineSim = CosineSimilarityUDF.cosineSimilarity(ftvec1, ftvec2);
return 1.0f - (float) (Math.acos(cosineSim) / Math.PI);
}
@Override
public String getDisplayString(String[] children) {
return "angular_similarity(" + Arrays.toString(children) + ")";
}
}