org.lenskit.pf.HPFItemScorer.java Source code

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Here is the source code for org.lenskit.pf.HPFItemScorer.java

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/*
 * LensKit, an open-source toolkit for recommender systems.
 * Copyright 2014-2017 LensKit contributors (see CONTRIBUTORS.md)
 * Copyright 2010-2014 Regents of the University of Minnesota
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
package org.lenskit.pf;

import it.unimi.dsi.fastutil.longs.LongIterator;
import it.unimi.dsi.fastutil.longs.LongIterators;
import org.apache.commons.math3.linear.RealVector;
import org.lenskit.api.Result;
import org.lenskit.api.ResultMap;
import org.lenskit.basic.AbstractItemScorer;
import org.lenskit.results.Results;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.annotation.Nonnull;
import javax.inject.Inject;
import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class HPFItemScorer extends AbstractItemScorer {
    private static Logger logger = LoggerFactory.getLogger(HPFItemScorer.class);

    private final HPFModel model;
    private final boolean isProbPrediction;

    @Inject
    public HPFItemScorer(HPFModel mod, @IsProbabilityPrediction boolean probPred) {
        model = mod;
        isProbPrediction = probPred;
    }

    @Nonnull
    @Override
    public ResultMap scoreWithDetails(long user, @Nonnull Collection<Long> items) {
        RealVector uvec = model.getUserVector(user);
        if (uvec == null) {
            return Results.newResultMap();
        }

        List<Result> results = new ArrayList<>(items.size());
        LongIterator iter = LongIterators.asLongIterator(items.iterator());
        while (iter.hasNext()) {
            long item = iter.nextLong();
            RealVector ivec = model.getItemVector(item);
            if (ivec != null) {
                double score = uvec.dotProduct(ivec);
                if (isProbPrediction) {
                    score = 1 - Math.exp(-score);
                }
                results.add(Results.create(item, score));
            }
        }
        return Results.newResultMap(results);
    }
}