org.gpfvic.mahout.cf.taste.hadoop.als.ALS.java Source code

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/**
 * 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.gpfvic.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<VectorWritable> iterator = new SequenceFileDirValueIterator<>(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) {
            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<Vector> readMatrixByRows(Path dir, Configuration conf) {
        OpenIntObjectHashMap<Vector> matrix = new OpenIntObjectHashMap<>();
        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 = 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);
    }
}