/*
* LensKit, an open source recommender systems toolkit.
* Copyright 2010-2014 LensKit Contributors. See CONTRIBUTORS.md.
* Work on LensKit has been funded by the National Science Foundation under
* grants IIS 05-34939, 08-08692, 08-12148, and 10-17697.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc., 51
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
package org.grouplens.lenskit.knn.item.model;
import it.unimi.dsi.fastutil.longs.Long2ObjectMap;
import it.unimi.dsi.fastutil.longs.Long2ObjectOpenHashMap;
import it.unimi.dsi.fastutil.longs.LongSortedSet;
import org.grouplens.lenskit.collections.LongKeyDomain;
import org.grouplens.lenskit.collections.LongUtils;
import org.grouplens.lenskit.core.Transient;
import org.grouplens.lenskit.cursors.Cursor;
import org.grouplens.lenskit.data.dao.UserEventDAO;
import org.grouplens.lenskit.data.event.Event;
import org.grouplens.lenskit.data.history.UserHistory;
import org.grouplens.lenskit.data.history.UserHistorySummarizer;
import org.grouplens.lenskit.scored.ScoredIdListBuilder;
import org.grouplens.lenskit.scored.ScoredIds;
import org.grouplens.lenskit.transform.normalize.UserVectorNormalizer;
import org.grouplens.lenskit.vectors.MutableSparseVector;
import org.grouplens.lenskit.vectors.SparseVector;
import org.grouplens.lenskit.vectors.VectorEntry;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.inject.Inject;
import javax.inject.Provider;
/**
* Provider that sets up an {@link ItemItemBuildContext}.
*
* @author <a href="http://www.grouplens.org">GroupLens Research</a>
*/
public class ItemItemBuildContextProvider implements Provider<ItemItemBuildContext> {
private static final Logger logger = LoggerFactory.getLogger(ItemItemBuildContextProvider.class);
private final UserEventDAO userEventDAO;
private final UserVectorNormalizer normalizer;
private final UserHistorySummarizer userSummarizer;
@Inject
public ItemItemBuildContextProvider(@Transient UserEventDAO edao,
@Transient UserVectorNormalizer normalizer,
@Transient UserHistorySummarizer userSummarizer) {
userEventDAO = edao;
this.normalizer = normalizer;
this.userSummarizer = userSummarizer;
}
/**
* Constructs and returns a new ItemItemBuildContext.
*
* @return a new ItemItemBuildContext.
*/
@Override
public ItemItemBuildContext get() {
logger.info("constructing build context");
logger.debug("using normalizer {}", normalizer);
logger.debug("using summarizer {}", userSummarizer);
logger.debug("Building item data");
Long2ObjectMap<ScoredIdListBuilder> itemRatingData = new Long2ObjectOpenHashMap<ScoredIdListBuilder>(1000);
Long2ObjectMap<LongSortedSet> userItems = new Long2ObjectOpenHashMap<LongSortedSet>(1000);
buildItemRatings(itemRatingData, userItems);
LongKeyDomain items = LongKeyDomain.fromCollection(itemRatingData.keySet(), true);
final int n = items.domainSize();
assert n == itemRatingData.size();
// finalize the item data into vectors
SparseVector[] itemRatings = new SparseVector[n];
for (int i = 0; i < n; i++) {
final long item = items.getKey(i);
ScoredIdListBuilder ratings = itemRatingData.get(item);
SparseVector v = ratings.buildVector();
assert v.size() == ratings.size();
itemRatings[i] = v;
// release some memory
ratings.clear();
}
logger.debug("item data completed");
return new ItemItemBuildContext(items, itemRatings, userItems);
}
/**
* Transpose the user matrix so we have a matrix of item ids to ratings. Accumulate user item vectors into
* the candidate sets for each item
*
* @param itemRatings mapping from item ids to (userId: rating) maps (to be filled)
* @param userItems mapping of user IDs to rated item sets to be filled.
*/
private void buildItemRatings(Long2ObjectMap<ScoredIdListBuilder> itemRatings,
Long2ObjectMap<LongSortedSet> userItems) {
// initialize the transposed array to collect item vector data
Cursor<UserHistory<Event>> users = userEventDAO.streamEventsByUser();
try {
for (UserHistory<Event> user : users) {
long uid = user.getUserId();
SparseVector summary = userSummarizer.summarize(user);
MutableSparseVector normed = summary.mutableCopy();
normalizer.normalize(uid, summary, normed);
for (VectorEntry rating : normed) {
final long item = rating.getKey();
// get the item's rating accumulator
ScoredIdListBuilder ivect = itemRatings.get(item);
if (ivect == null) {
ivect = ScoredIds.newListBuilder(100);
itemRatings.put(item, ivect);
}
ivect.add(uid, rating.getValue());
}
// get the item's candidate set
userItems.put(uid, LongUtils.packedSet(summary.keySet()));
}
} finally {
users.close();
}
}
}