/**
* 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 org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.IntWritable;
import org.apache.mahout.math.VectorWritable;
import org.apache.mahout.math.als.ImplicitFeedbackAlternatingLeastSquaresSolver;
import java.io.IOException;
/** Solving mapper that can be safely executed using multiple threads */
public class SolveImplicitFeedbackMapper
extends SharingMapper<IntWritable,VectorWritable,IntWritable,VectorWritable,
ImplicitFeedbackAlternatingLeastSquaresSolver> {
private final VectorWritable uiOrmj = new VectorWritable();
@Override
ImplicitFeedbackAlternatingLeastSquaresSolver createSharedInstance(Context ctx) throws IOException {
Configuration conf = ctx.getConfiguration();
double lambda = Double.parseDouble(conf.get(ParallelALSFactorizationJob.LAMBDA));
double alpha = Double.parseDouble(conf.get(ParallelALSFactorizationJob.ALPHA));
int numFeatures = conf.getInt(ParallelALSFactorizationJob.NUM_FEATURES, -1);
int numEntities = Integer.parseInt(conf.get(ParallelALSFactorizationJob.NUM_ENTITIES));
Preconditions.checkArgument(numFeatures > 0, "numFeatures was not set correctly!");
return new ImplicitFeedbackAlternatingLeastSquaresSolver(numFeatures, lambda, alpha,
ALS.readMatrixByRowsFromDistributedCache(numEntities, conf));
}
@Override
protected void map(IntWritable userOrItemID, VectorWritable ratingsWritable, Context ctx)
throws IOException, InterruptedException {
ImplicitFeedbackAlternatingLeastSquaresSolver solver = getSharedInstance();
uiOrmj.set(solver.solve(ratingsWritable.get()));
ctx.write(userOrItemID, uiOrmj);
}
}