public void TestMostSimilar()
{
ItemBasedRecommender recommender = buildRecommender();
IList <RecommendedItem> similar = recommender.MostSimilarItems("0", 2);
Assert.IsNotNull(similar);
Assert.AreEqual(2, similar.Count);
RecommendedItem first = similar[0];
RecommendedItem second = similar[1];
Assert.AreEqual("1", first.Item.ID);
Assert.AreEqual(1.0, first.Value, EPSILON);
Assert.AreEqual("2", second.Item.ID);
Assert.AreEqual(0.5, second.Value, EPSILON);
}
public void testRecommendedBecause()
{
ItemBasedRecommender recommender = buildRecommender2();
IList <RecommendedItem> recommendedBecause = recommender.RecommendedBecause("test1", "4", 3);
Assert.IsNotNull(recommendedBecause);
Assert.AreEqual(3, recommendedBecause.Count);
RecommendedItem first = recommendedBecause[0];
RecommendedItem second = recommendedBecause[1];
RecommendedItem third = recommendedBecause[2];
Assert.AreEqual("2", first.Item.ID);
Assert.AreEqual(0.99, first.Value, EPSILON);
Assert.AreEqual("3", second.Item.ID);
Assert.AreEqual(0.4, second.Value, EPSILON);
Assert.AreEqual("0", third.Item.ID);
Assert.AreEqual(0.2, third.Value, EPSILON);
}
public List <MovieViewModel> GetSuggestions(string userId, int numSuggestions, UserMovieRatingsTable table)
{
int userIndex = table.UserIndexToId.IndexOf(userId);
UserMoviesRatings user = table.Users[userIndex];
List <Suggestion> suggestions = new List <Suggestion>();
List <UserMoviesRatings> neighbors = GetNearestNeighbors(userId, user, 5, table);
if (neighbors.ToList()[0].Score <= 0.5)
{
ItemBasedRecommender itemBasedRecommender = new ItemBasedRecommender(_mapper, _movieRepository);
return(itemBasedRecommender.GetSuggestions(userId, 10, table));
}
for (int movieIndex = 0; movieIndex < table.MovieIndexToId.Count; movieIndex++)
{
if (user.MovieRatings[movieIndex] != 0)
{
double score = 0.0;
int count = 0;
for (var u = 0; u < neighbors.Count; u++)
{
if (neighbors[u].MovieRatings[movieIndex] != 0)
{
score += neighbors[u].MovieRatings[movieIndex] - ((u + 1.0) / 100.0);
count++;
}
}
if (count > 0)
{
score /= count;
}
suggestions.Add(new Suggestion(userId, table.MovieIndexToId[movieIndex], score));
}
}
suggestions.Sort((c, n) => n.Rating.CompareTo(c.Rating));
List <Suggestion> suggestionsList = suggestions.Take(numSuggestions).ToList();
List <MovieViewModel> movieViewModels = new List <MovieViewModel>();
foreach (var suggestion in suggestionsList)
{
Movie movie = _movieRepository.GetById(suggestion.MovieId);
movieViewModels.Add(_mapper.Map <MovieViewModel>(movie));
}
return(movieViewModels);
}
public void TestMostSimilarToMultiple()
{
ItemBasedRecommender recommender = buildRecommender2();
List <Object> itemIDs = new List <Object>(2);
itemIDs.Add("0");
itemIDs.Add("1");
IList <RecommendedItem> similar = recommender.MostSimilarItems(itemIDs, 2);
Assert.IsNotNull(similar);
Assert.AreEqual(2, similar.Count);
RecommendedItem first = similar[0];
RecommendedItem second = similar[1];
Assert.AreEqual("2", first.Item.ID);
Assert.AreEqual(0.85, first.Value, EPSILON);
Assert.AreEqual("3", second.Item.ID);
Assert.AreEqual(-0.3, second.Value, EPSILON);
}
protected BatchItemSimilarities(ItemBasedRecommender recommender, int similarItemsPerItem)
{
this.recommender = recommender;
this.similarItemsPerItem = similarItemsPerItem;
}
/// @param recommender recommender to use
/// @param similarItemsPerItem number of similar items to compute per item
/// @param batchSize size of item batches sent to worker threads
public MultithreadedBatchItemSimilarities(ItemBasedRecommender recommender, int similarItemsPerItem, int batchSize) :
base(recommender, similarItemsPerItem) {
this.batchSize = batchSize;
}
/// @param recommender recommender to use
/// @param similarItemsPerItem number of similar items to compute per item
public MultithreadedBatchItemSimilarities(ItemBasedRecommender recommender, int similarItemsPerItem) :
this(recommender, similarItemsPerItem, DEFAULT_BATCH_SIZE) {
}