@Override
public void predict(long uid, @Nonnull MutableSparseVector predictions) {
logger.debug("predicting {} items for {}", predictions.keyDomain().size(), uid);
OrdRecModel params = new OrdRecModel(quantizer);
SparseVector ratings = makeUserVector(uid, userEventDao);
LongSet keySet = LongUtils.setUnion(ratings.keySet(), predictions.keyDomain());
MutableSparseVector scores = MutableSparseVector.create(keySet);
itemScorer.score(uid, scores);
params.train(ratings, scores);
logger.debug("trained parameters for {}: {}", uid, params);
Vector probabilities = Vector.createLength(params.getLevelCount());
Long2ObjectMap<IVector> distChannel = null;
if (reportDistribution) {
distChannel = predictions.addChannel(RATING_PROBABILITY_CHANNEL);
}
for (VectorEntry e : predictions.fast(VectorEntry.State.EITHER)) {
long iid = e.getKey();
double score = scores.get(iid);
params.getProbDistribution(score, probabilities);
int mlIdx = probabilities.maxElementIndex();
predictions.set(e, quantizer.getIndexValue(mlIdx));
if (distChannel != null) {
distChannel.put(e.getKey(), probabilities.immutable());
}
}
}
/**
* Build a rating matrix from the rating data. Each user's ratings are first normalized by
* subtracting a baseline score (usually a mean).
*
* @param userMapping The index mapping of user IDs to column numbers.
* @param itemMapping The index mapping of item IDs to row numbers.
* @return A matrix storing the <i>normalized</i> user ratings.
*/
private RealMatrix createRatingMatrix(IdIndexMapping userMapping, IdIndexMapping itemMapping) {
final int nusers = userMapping.size();
final int nitems = itemMapping.size();
// Create a matrix with users on rows and items on columns
logger.info("creating {} by {} rating matrix", nusers, nitems);
RealMatrix matrix = MatrixUtils.createRealMatrix(nusers, nitems);
// populate it with data
Cursor<UserHistory<Event>> users = userEventDAO.streamEventsByUser();
try {
for (UserHistory<Event> user : users) {
// Get the row number for this user
int u = userMapping.getIndex(user.getUserId());
MutableSparseVector ratings = Ratings.userRatingVector(user.filter(Rating.class));
MutableSparseVector baselines = MutableSparseVector.create(ratings.keySet());
baselineScorer.score(user.getUserId(), baselines);
// TODO Populate this user's row with their ratings, minus the baseline scores
for (VectorEntry entry : ratings.fast(State.SET)) {
long itemid = entry.getKey();
int i = itemMapping.getIndex(itemid);
double rating = entry.getValue();
double baseline = baselines.get(itemid);
matrix.setEntry(u, i, rating - baseline);
}
}
} finally {
users.close();
}
return matrix;
}
/**
* Score items in a vector. The key domain of the provided vector is the items to score, and the
* score method sets the values for each item to its score (or unsets it, if no score can be
* provided). The previous values are discarded.
*
* @param user The user ID.
* @param scores The score vector.
*/
@Override
public void score(long user, @Nonnull MutableSparseVector scores) {
// TODO Score the items in the key domain of scores
for (VectorEntry e : scores.fast(VectorEntry.State.EITHER)) {
long item = e.getKey();
// TODO Set the scores
double score = prediction(user, item);
scores.set(e, score);
}
}
@Override
@SuppressWarnings({"rawtypes", "unchecked"})
public void execute() throws IOException, RecommenderBuildException {
LenskitRecommenderEngine engine = loadEngine();
long user = options.getLong("user");
List<Long> items = options.get("items");
LenskitRecommender rec = engine.createRecommender();
RatingPredictor pred = rec.getRatingPredictor();
if (pred == null) {
logger.error("recommender has no rating predictor");
throw new UnsupportedOperationException("no rating predictor");
}
logger.info("predicting {} items", items.size());
Symbol pchan = getPrintChannel();
Stopwatch timer = Stopwatch.createStarted();
SparseVector preds = pred.predict(user, items);
Long2ObjectMap channel = null;
if (pchan != null) {
for (TypedSymbol sym : preds.getChannelSymbols()) {
if (sym.getRawSymbol().equals(pchan)) {
channel = preds.getChannel(sym);
}
}
}
for (VectorEntry e : preds) {
System.out.format(" %d: %.3f", e.getKey(), e.getValue());
if (channel != null) {
System.out.format(" (%s)", channel.get(e.getKey()));
}
System.out.println();
}
timer.stop();
logger.info("predicted for {} items in {}", items.size(), timer);
}
/** The train function of OrdRec. Get all parameters after learning process. */
@SuppressWarnings("ConstantConditions")
private void train(SparseVector ratings, MutableSparseVector scores) {
Vector dbeta = Vector.createLength(beta.length());
double dt1;
// n is the number of iteration;
for (int j = 0; j < iterationCount; j++) {
for (VectorEntry rating : ratings.fast()) {
long iid = rating.getKey();
double score = scores.get(iid);
int r = quantizer.index(rating.getValue());
double probEqualR = getProbEQ(score, r);
double probLessR = getProbLE(score, r);
double probLessR_1 = getProbLE(score, r - 1);
dt1 =
learningRate
/ probEqualR
* (probLessR * (1 - probLessR) * derivateOfBeta(r, 0, t1)
- probLessR_1 * (1 - probLessR_1) * derivateOfBeta(r - 1, 0, t1)
- regTerm * t1);
double dbetaK;
for (int k = 0; k < beta.length(); k++) {
dbetaK =
learningRate
/ probEqualR
* (probLessR * (1 - probLessR) * derivateOfBeta(r, k + 1, beta.get(k))
- probLessR_1
* (1 - probLessR_1)
* derivateOfBeta(r - 1, k + 1, beta.get(k))
- regTerm * beta.get(k));
dbeta.set(k, dbetaK);
}
t1 = t1 + dt1;
beta.add(dbeta);
}
}
}
/**
* This method is where the model should actually be computed.
*
* @return The TF-IDF model (a model of item tag vectors).
*/
@Override
public TFIDFModel get() {
// Build a map of tags to numeric IDs. This lets you convert tags (which are strings)
// into long IDs that you can use as keys in a tag vector.
Map<String, Long> tagIds = buildTagIdMap();
// Create a vector to accumulate document frequencies for the IDF computation
MutableSparseVector docFreq = MutableSparseVector.create(tagIds.values());
docFreq.fill(0);
// We now proceed in 2 stages. First, we build a TF vector for each item.
// While we do this, we also build the DF vector.
// We will then apply the IDF to each TF vector and normalize it to a unit vector.
// Create a map to store the item TF vectors.
Map<Long, MutableSparseVector> itemVectors = Maps.newHashMap();
// Create a work vector to accumulate each item's tag vector.
// This vector will be re-used for each item.
MutableSparseVector work = MutableSparseVector.create(tagIds.values());
// Iterate over the items to compute each item's vector.
LongSet items = dao.getItemIds();
for (long item : items) {
// Reset the work vector for this item's tags.
work.clear();
// Now the vector is empty (all keys are 'unset').
List<String> hashtag = new ArrayList<String>();
for (String tag : dao.getItemTags(item)) {
Long id = tagIds.get(tag);
try {
// if id is not in the key set, throw the Exception.
work.set(id, work.get(id) + 1);
} catch (Exception e) {
// if you catch the Exception, which means that id has not been set yet.
work.set(id, 1.0); // use set method to "set" the Key
}
if (!hashtag.contains(tag)) {
docFreq.set(id, docFreq.get(id) + 1);
hashtag.add(tag);
}
}
// Save a shrunk copy of the vector (only storing tags that apply to this item) in
// our map, we'll add IDF and normalize later.
itemVectors.put(item, work.shrinkDomain());
// work is ready to be reset and re-used for the next item
}
// Now we've seen all the items, so we have each item's TF vector and a global vector
// of document frequencies.
// Invert and log the document frequency. We can do this in-place.
for (VectorEntry e : docFreq.fast()) {
docFreq.set(e.getKey(), Math.log(items.size() / e.getValue()));
}
// Now docFreq is a log-IDF vector.
// So we can use it to apply IDF to each item vector to put it in the final model.
// Create a map to store the final model data.
Map<Long, SparseVector> modelData = Maps.newHashMap();
for (Map.Entry<Long, MutableSparseVector> entry : itemVectors.entrySet()) {
MutableSparseVector tv = entry.getValue();
// DA FARE Convert this vector to a TF-IDF vector
for (VectorEntry e : tv.fast()) {
tv.set(e.getKey(), ((e.getValue() * docFreq.get(e.getKey()))));
}
// DA FARE Normalize the TF-IDF vector to be a unit vector
// HINT The method tv.norm() will give you the Euclidian length of the vector
tv.multiply(1 / tv.norm());
// Store a frozen (immutable) version of the vector in the model data.
modelData.put(entry.getKey(), tv.freeze());
}
// we technically don't need the IDF vector anymore, so long as we have no new tags
return new TFIDFModel(tagIds, modelData);
}