/// <summary>
/// Finds related users for every user in a instance source.
/// The subset of users who will be returned as related for a particular user is restricted:
/// it is guaranteed that all the related users have rated at least <paramref name="minCommonRatingCount"/> items in common with the query user
/// in the dataset.
/// </summary>
/// <typeparam name="TFeatureSource">The type of a feature source used by the recommendation engine.</typeparam>
/// <param name="recommender">The recommendation engine.</param>
/// <param name="instanceSource">The instance source.</param>
/// <param name="maxRelatedUserCount">Maximum number of related users to return.</param>
/// <param name="minCommonRatingCount">Minimum number of items that the query user and the related user should have rated in common.</param>
/// <param name="minRelatedUserPoolSize">
/// If a user has less than <paramref name="minRelatedUserPoolSize"/> possible related users,
/// it will be skipped.
/// </param>
/// <param name="featureSource">The source of features.</param>
/// <returns>The list of related users for every user in <paramref name="instanceSource"/>.</returns>
public IDictionary <TUser, IEnumerable <TUser> > FindRelatedUsersWhoRatedSameItems <TFeatureSource>(
IRecommender <TInstanceSource, TUser, TItem, TPredictedRating, TPredictedRatingDist, TFeatureSource> recommender,
TInstanceSource instanceSource,
int maxRelatedUserCount,
int minCommonRatingCount,
int minRelatedUserPoolSize,
TFeatureSource featureSource = default(TFeatureSource))
{
if (recommender == null)
{
throw new ArgumentNullException("recommender");
}
if (maxRelatedUserCount <= 0)
{
throw new ArgumentOutOfRangeException("maxRelatedUserCount", "The maximum number of related users should be positive.");
}
if (minCommonRatingCount <= 0)
{
throw new ArgumentOutOfRangeException("minCommonRatingCount", "The minimum number of common ratings should be positive.");
}
if (minRelatedUserPoolSize <= 0)
{
throw new ArgumentOutOfRangeException("minRelatedUserPoolSize", "The minimum size of the related users pool should be positive.");
}
return(FindRelatedEntitiesWhichRatedTheSame(
this.mapping.GetUsers(instanceSource),
user => this.mapping.GetUsersWhoRatedSameItems(instanceSource, user),
(user, userSubset) =>
{
recommender.UserSubset = userSubset;
return recommender.GetRelatedUsers(user, maxRelatedUserCount, featureSource);
},
minCommonRatingCount,
minRelatedUserPoolSize));
}
