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