Factorization.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.Arrays;
import java.util.Map;

import org.codelibs.elasticsearch.taste.common.FastByIDMap;
import org.codelibs.elasticsearch.taste.exception.NoSuchItemException;
import org.codelibs.elasticsearch.taste.exception.NoSuchUserException;

import com.google.common.base.Preconditions;

/**
 * a factorization of the rating matrix
 */
public class Factorization {

    /** used to find the rows in the user features matrix by userID */
    private final FastByIDMap<Integer> userIDMapping;

    /** used to find the rows in the item features matrix by itemID */
    private final FastByIDMap<Integer> itemIDMapping;

    /** user features matrix */
    private final double[][] userFeatures;

    /** item features matrix */
    private final double[][] itemFeatures;

    public Factorization(final FastByIDMap<Integer> userIDMapping,
            final FastByIDMap<Integer> itemIDMapping,
            final double[][] userFeatures, final double[][] itemFeatures) {
        this.userIDMapping = Preconditions.checkNotNull(userIDMapping);
        this.itemIDMapping = Preconditions.checkNotNull(itemIDMapping);
        this.userFeatures = userFeatures;
        this.itemFeatures = itemFeatures;
    }

    public double[][] allUserFeatures() {
        return userFeatures;
    }

    public double[] getUserFeatures(final long userID)
            throws NoSuchUserException {
        final Integer index = userIDMapping.get(userID);
        if (index == null) {
            throw new NoSuchUserException(userID);
        }
        return userFeatures[index];
    }

    public double[][] allItemFeatures() {
        return itemFeatures;
    }

    public double[] getItemFeatures(final long itemID)
            throws NoSuchItemException {
        final Integer index = itemIDMapping.get(itemID);
        if (index == null) {
            throw new NoSuchItemException(itemID);
        }
        return itemFeatures[index];
    }

    public int userIndex(final long userID) throws NoSuchUserException {
        final Integer index = userIDMapping.get(userID);
        if (index == null) {
            throw new NoSuchUserException(userID);
        }
        return index;
    }

    public Iterable<Map.Entry<Long, Integer>> getUserIDMappings() {
        return userIDMapping.entrySet();
    }

    public int itemIndex(final long itemID) throws NoSuchItemException {
        final Integer index = itemIDMapping.get(itemID);
        if (index == null) {
            throw new NoSuchItemException(itemID);
        }
        return index;
    }

    public Iterable<Map.Entry<Long, Integer>> getItemIDMappings() {
        return itemIDMapping.entrySet();
    }

    public int numFeatures() {
        return userFeatures.length > 0 ? userFeatures[0].length : 0;
    }

    public int numUsers() {
        return userIDMapping.size();
    }

    public int numItems() {
        return itemIDMapping.size();
    }

    @Override
    public boolean equals(final Object o) {
        if (o instanceof Factorization) {
            final Factorization other = (Factorization) o;
            return userIDMapping.equals(other.userIDMapping)
                    && itemIDMapping.equals(other.itemIDMapping)
                    && Arrays.deepEquals(userFeatures, other.userFeatures)
                    && Arrays.deepEquals(itemFeatures, other.itemFeatures);
        }
        return false;
    }

    @Override
    public int hashCode() {
        int hashCode = 31 * userIDMapping.hashCode() + itemIDMapping.hashCode();
        hashCode = 31 * hashCode + Arrays.deepHashCode(userFeatures);
        hashCode = 31 * hashCode + Arrays.deepHashCode(itemFeatures);
        return hashCode;
    }
}