| /* |
| * 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.lucene.queries.function.valuesource; |
| |
| import org.apache.lucene.index.LeafReaderContext; |
| import org.apache.lucene.queries.function.FunctionValues; |
| import org.apache.lucene.queries.function.ValueSource; |
| import org.apache.lucene.queries.function.docvalues.FloatDocValues; |
| import org.apache.lucene.search.IndexSearcher; |
| |
| import java.io.IOException; |
| import java.util.Map; |
| |
| /** |
| * <code>ReciprocalFloatFunction</code> implements a reciprocal function f(x) = a/(mx+b), based on |
| * the float value of a field or function as exported by {@link org.apache.lucene.queries.function.ValueSource}. |
| * <br> |
| * |
| * When a and b are equal, and x>=0, this function has a maximum value of 1 that drops as x increases. |
| * Increasing the value of a and b together results in a movement of the entire function to a flatter part of the curve. |
| * <p>These properties make this an idea function for boosting more recent documents. |
| * <p>Example:<code> recip(ms(NOW,mydatefield),3.16e-11,1,1)</code> |
| * <p>A multiplier of 3.16e-11 changes the units from milliseconds to years (since there are about 3.16e10 milliseconds |
| * per year). Thus, a very recent date will yield a value close to 1/(0+1) or 1, |
| * a date a year in the past will get a multiplier of about 1/(1+1) or 1/2, |
| * and date two years old will yield 1/(2+1) or 1/3. |
| * |
| * @see org.apache.lucene.queries.function.FunctionQuery |
| * |
| * |
| */ |
| public class ReciprocalFloatFunction extends ValueSource { |
| protected final ValueSource source; |
| protected final float m; |
| protected final float a; |
| protected final float b; |
| |
| /** |
| * f(source) = a/(m*float(source)+b) |
| */ |
| public ReciprocalFloatFunction(ValueSource source, float m, float a, float b) { |
| this.source=source; |
| this.m=m; |
| this.a=a; |
| this.b=b; |
| } |
| |
| @Override |
| public FunctionValues getValues(Map context, LeafReaderContext readerContext) throws IOException { |
| final FunctionValues vals = source.getValues(context, readerContext); |
| return new FloatDocValues(this) { |
| @Override |
| public float floatVal(int doc) throws IOException { |
| return a/(m*vals.floatVal(doc) + b); |
| } |
| @Override |
| public boolean exists(int doc) throws IOException { |
| return vals.exists(doc); |
| } |
| @Override |
| public String toString(int doc) throws IOException { |
| return Float.toString(a) + "/(" |
| + m + "*float(" + vals.toString(doc) + ')' |
| + '+' + b + ')'; |
| } |
| }; |
| } |
| |
| @Override |
| public void createWeight(Map context, IndexSearcher searcher) throws IOException { |
| source.createWeight(context, searcher); |
| } |
| |
| @Override |
| public String description() { |
| return Float.toString(a) + "/(" |
| + m + "*float(" + source.description() + ")" |
| + "+" + b + ')'; |
| } |
| |
| @Override |
| public int hashCode() { |
| int h = Float.floatToIntBits(a) + Float.floatToIntBits(m); |
| h ^= (h << 13) | (h >>> 20); |
| return h + (Float.floatToIntBits(b)) + source.hashCode(); |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (ReciprocalFloatFunction.class != o.getClass()) return false; |
| ReciprocalFloatFunction other = (ReciprocalFloatFunction)o; |
| return this.m == other.m |
| && this.a == other.a |
| && this.b == other.b |
| && this.source.equals(other.source); |
| } |
| } |