/// <summary>
/// Scores the users in <see cref="usageEvents"/> who are also present in <see cref="evaluationUsageEvents"/>
/// </summary>
/// <param name="model">Model to be used for scoring</param>
/// <param name="usageEvents">List of usage events</param>
/// <param name="evaluationUsageEvents">List of evaluation events</param>
/// <returns></returns>
private IList <SarScoreResult> ScoreTestUsers(ITrainedModel model, IList <SarUsageEvent> usageEvents,
IList <SarUsageEvent> evaluationUsageEvents)
{
// Score the test users
var evaluationRecommender = new Recommender(model, null, _tracer);
// extract the user ids from the evaluation usage events
HashSet <uint> evaluationUsers = new HashSet <uint>(evaluationUsageEvents.Select(usageEvent => usageEvent.UserId));
// filter out usage events of users not found in the evaluation set
IEnumerable <SarUsageEvent> usageEventsFiltered =
usageEvents.Where(usageEvent => evaluationUsers.Contains(usageEvent.UserId));
// group usage event by user, and calculate score
List <SarScoreResult> scores =
usageEventsFiltered.GroupBy(usageEvent => usageEvent.UserId)
.SelectMany(group => evaluationRecommender.ScoreUsageEvents(group.ToList(), RecommendationCount))
.ToList();
return(scores);
}