org.apache.mahout.vectorizer.encoders.WordValueEncoder Maven / Gradle / Ivy
/*
* 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.vectorizer.encoders;
import org.apache.mahout.math.Vector;
import java.util.Locale;
/**
* Encodes words as sparse vector updates to a Vector. Weighting is defined by a
* sub-class.
*/
public abstract class WordValueEncoder extends FeatureVectorEncoder {
private final byte[] nameBytes;
protected WordValueEncoder(String name) {
super(name, 2);
nameBytes = bytesForString(name);
}
/**
* Adds a value to a vector.
*
* @param originalForm The original form of the value as a string.
* @param data The vector to which the value should be added.
*/
@Override
public void addToVector(byte[] originalForm, double w, Vector data) {
int probes = getProbes();
String name = getName();
double weight = getWeight(originalForm, w);
for (int i = 0; i < probes; i++) {
int n = hashForProbe(originalForm, data.size(), name, i);
if (isTraceEnabled()) {
trace(originalForm, n);
}
data.set(n, data.get(n) + weight);
}
}
@Override
protected double getWeight(byte[] originalForm, double w) {
return w * weight(originalForm);
}
@Override
protected int hashForProbe(byte[] originalForm, int dataSize, String name, int probe) {
return hash(nameBytes, originalForm, WORD_LIKE_VALUE_HASH_SEED + probe, dataSize);
}
/**
* Converts a value into a form that would help a human understand the internals of how the value
* is being interpreted. For text-like things, this is likely to be a list of the terms found with
* associated weights (if any).
*
* @param originalForm The original form of the value as a string.
* @return A string that a human can read.
*/
@Override
public String asString(String originalForm) {
return String.format(Locale.ENGLISH, "%s:%s:%.4f", getName(), originalForm, weight(bytesForString(originalForm)));
}
protected abstract double weight(byte[] originalForm);
}