AbstractFactorizer.java

/**
 * 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.codelibs.elasticsearch.taste.recommender.svd;

import java.util.Collection;

import org.codelibs.elasticsearch.taste.common.FastByIDMap;
import org.codelibs.elasticsearch.taste.common.LongPrimitiveIterator;
import org.codelibs.elasticsearch.taste.common.RefreshHelper;
import org.codelibs.elasticsearch.taste.common.Refreshable;
import org.codelibs.elasticsearch.taste.model.DataModel;

/**
 * base class for {@link Factorizer}s, provides ID to index mapping
 */
public abstract class AbstractFactorizer implements Factorizer {

    private final DataModel dataModel;

    private FastByIDMap<Integer> userIDMapping;

    private FastByIDMap<Integer> itemIDMapping;

    private final RefreshHelper refreshHelper;

    protected AbstractFactorizer(final DataModel dataModel) {
        this.dataModel = dataModel;
        buildMappings();
        refreshHelper = new RefreshHelper(() -> {
            buildMappings();
            return null;
        });
        refreshHelper.addDependency(dataModel);
    }

    private void buildMappings() {
        userIDMapping = createIDMapping(dataModel.getNumUsers(),
                dataModel.getUserIDs());
        itemIDMapping = createIDMapping(dataModel.getNumItems(),
                dataModel.getItemIDs());
    }

    protected Factorization createFactorization(final double[][] userFeatures,
            final double[][] itemFeatures) {
        return new Factorization(userIDMapping, itemIDMapping, userFeatures,
                itemFeatures);
    }

    protected Integer userIndex(final long userID) {
        Integer userIndex = userIDMapping.get(userID);
        if (userIndex == null) {
            userIndex = userIDMapping.size();
            userIDMapping.put(userID, userIndex);
        }
        return userIndex;
    }

    protected Integer itemIndex(final long itemID) {
        Integer itemIndex = itemIDMapping.get(itemID);
        if (itemIndex == null) {
            itemIndex = itemIDMapping.size();
            itemIDMapping.put(itemID, itemIndex);
        }
        return itemIndex;
    }

    private static FastByIDMap<Integer> createIDMapping(final int size,
            final LongPrimitiveIterator idIterator) {
        final FastByIDMap<Integer> mapping = new FastByIDMap<>(size);
        int index = 0;
        while (idIterator.hasNext()) {
            mapping.put(idIterator.nextLong(), index++);
        }
        return mapping;
    }

    @Override
    public void refresh(final Collection<Refreshable> alreadyRefreshed) {
        refreshHelper.refresh(alreadyRefreshed);
    }

}