org.apache.mahout.cf.taste.hadoop.als.ALS 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.cf.taste.hadoop.als;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import com.google.common.base.Preconditions;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.LocalFileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.SequenceFile;
import org.apache.mahout.common.HadoopUtil;
import org.apache.mahout.common.Pair;
import org.apache.mahout.common.iterator.sequencefile.PathFilters;
import org.apache.mahout.common.iterator.sequencefile.PathType;
import org.apache.mahout.common.iterator.sequencefile.SequenceFileDirIterable;
import org.apache.mahout.common.iterator.sequencefile.SequenceFileDirValueIterator;
import org.apache.mahout.math.Vector;
import org.apache.mahout.math.VectorWritable;
import org.apache.mahout.math.als.AlternatingLeastSquaresSolver;
import org.apache.mahout.math.map.OpenIntObjectHashMap;
final class ALS {
private ALS() {}
static Vector readFirstRow(Path dir, Configuration conf) throws IOException {
Iterator iterator = new SequenceFileDirValueIterator<>(dir, PathType.LIST,
PathFilters.partFilter(), null, true, conf);
return iterator.hasNext() ? iterator.next().get() : null;
}
public static OpenIntObjectHashMap readMatrixByRowsFromDistributedCache(int numEntities,
Configuration conf) throws IOException {
IntWritable rowIndex = new IntWritable();
VectorWritable row = new VectorWritable();
OpenIntObjectHashMap featureMatrix = numEntities > 0
? new OpenIntObjectHashMap(numEntities) : new OpenIntObjectHashMap();
Path[] cachedFiles = HadoopUtil.getCachedFiles(conf);
LocalFileSystem localFs = FileSystem.getLocal(conf);
for (Path cachedFile : cachedFiles) {
try (SequenceFile.Reader reader = new SequenceFile.Reader(localFs, cachedFile, conf)){
while (reader.next(rowIndex, row)) {
featureMatrix.put(rowIndex.get(), row.get());
}
}
}
Preconditions.checkState(!featureMatrix.isEmpty(), "Feature matrix is empty");
return featureMatrix;
}
public static OpenIntObjectHashMap readMatrixByRows(Path dir, Configuration conf) {
OpenIntObjectHashMap matrix = new OpenIntObjectHashMap<>();
for (Pair pair
: new SequenceFileDirIterable(dir, PathType.LIST, PathFilters.partFilter(), conf)) {
int rowIndex = pair.getFirst().get();
Vector row = pair.getSecond().get();
matrix.put(rowIndex, row);
}
return matrix;
}
public static Vector solveExplicit(VectorWritable ratingsWritable, OpenIntObjectHashMap uOrM,
double lambda, int numFeatures) {
Vector ratings = ratingsWritable.get();
List featureVectors = new ArrayList<>(ratings.getNumNondefaultElements());
for (Vector.Element e : ratings.nonZeroes()) {
int index = e.index();
featureVectors.add(uOrM.get(index));
}
return AlternatingLeastSquaresSolver.solve(featureVectors, ratings, lambda, numFeatures);
}
}