org.grouplens.lenskit.basic

Class TopNGlobalItemRecommender

java.lang.Object

org.grouplens.lenskit.basic.AbstractGlobalItemRecommender

org.grouplens.lenskit.basic.TopNGlobalItemRecommender

All Implemented Interfaces:

GlobalItemRecommender

public class TopNGlobalItemRecommender
extends AbstractGlobalItemRecommender

A global item recommender that recommends the top N items from a scorer.

Since:

1.1

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	TopNGlobalItemRecommender.Provider An intelligent provider for Top-N global recommenders.

Field Summary

Fields

Modifier and Type	Field and Description
protected ItemDAO	itemDAO
protected GlobalItemScorer	scorer

Constructor Summary

Constructors

Constructor and Description
TopNGlobalItemRecommender(ItemDAO idao, GlobalItemScorer scorer)

Method Summary

Modifier and Type	Method and Description
protected LongSet	getDefaultExcludes(LongSet items) Get the default exclude set for a item in the global recommendation.
protected List<ScoredId>	globalRecommend(LongSet items, int n, LongSet candidates, LongSet exclude) Implement the ID-based recommendation in terms of the scorer.
protected List<ScoredId>	recommend(int n, SparseVector scores) Pick the top n items from a score vector.

Methods inherited from class org.grouplens.lenskit.basic.AbstractGlobalItemRecommender

globalRecommend, globalRecommend, globalRecommend, globalRecommend

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

itemDAO

protected final ItemDAO itemDAO

scorer

protected final GlobalItemScorer scorer

Constructor Detail

TopNGlobalItemRecommender

public TopNGlobalItemRecommender(ItemDAO idao,
                                 GlobalItemScorer scorer)

Method Detail

globalRecommend

protected List<ScoredId> globalRecommend(LongSet items,
                                         int n,
                                         LongSet candidates,
                                         LongSet exclude)

Implement the ID-based recommendation in terms of the scorer. This method uses getDefaultExcludes(LongSet) to supply a missing exclude set.

Specified by:

globalRecommend in class AbstractGlobalItemRecommender

Parameters:

items - The items ID.

n - The number of items to return, or negative to return all possible items.

candidates - The candidate set.

exclude - The set of excluded items, or null to use the default exclude set.

Returns:

A scored list of item IDs.

See Also:

GlobalItemRecommender.globalRecommend(Set, int, Set, Set)

getDefaultExcludes

protected LongSet getDefaultExcludes(LongSet items)

Get the default exclude set for a item in the global recommendation. The base implementation returns the input set.

Parameters:

items - The items for which we are recommending.

Returns:

The set of items to exclude.

recommend

protected List<ScoredId> recommend(int n,
                                   SparseVector scores)

Pick the top n items from a score vector.

Parameters:

n - The number of items to recommend.

scores - The scored item vector.

Returns:

The top n items from scores, in descending order of score.