public override bool Equals(Object o)
{
if (!(o is GenericRecommendedItem))
{
return(false);
}
GenericRecommendedItem other = (GenericRecommendedItem)o;
return(item.Equals(other.item) && value == other.value);
}
public static IList <RecommendedItem> GetTopItems(int howMany,
IEnumerable <Item> allItems,
Rescorer <Item> rescorer,
Estimator <Item> estimator)
{
if (allItems == null || rescorer == null || estimator == null)
{
throw new ArgumentNullException("argument is null");
}
LinkedList <RecommendedItem> topItems = new LinkedList <RecommendedItem>();
bool full = false;
foreach (Item item in allItems)
{
if (item.IsRecommendable && !rescorer.IsFiltered(item))
{
double preference = estimator.Estimate(item);
double rescoredPref = rescorer.Rescore(item, preference);
LinkedListNode <RecommendedItem> node = topItems.Last;
if (!Double.IsNaN(rescoredPref) &&
(!full || rescoredPref > node.Value.Value))
{
// I think this is faster than Collections.binarySearch() over a LinkedList since our
// comparisons are cheap, which binarySearch() economizes at the expense of more traversals.
// We also know that the right position tends to be at the end of the list.
while (node != null && node.Previous != null)
{
node = node.Previous;
if (rescoredPref <= node.Value.Value)
{
node = node.Next;
break;
}
if (node == topItems.First)
{
break;
}
}
RecommendedItem newItem = new GenericRecommendedItem(item, rescoredPref);
if (node == null)
{
topItems.AddFirst(newItem);
}
else if (topItems.Count == 1)
{
// special handling in this case is to avoid problems
// with negative preferences. Imagine -0.3 being added
// first followed by -0.6. If we simply did AddAfter,
// those items would be out of sequence - cc
if (rescoredPref > node.Value.Value)
{
topItems.AddAfter(node, newItem);
}
else
{
topItems.AddBefore(node, newItem);
}
}
else
{
topItems.AddAfter(node, newItem);
}
if (full)
{
topItems.RemoveLast();
}
else if (topItems.Count > howMany)
{
full = true;
topItems.RemoveLast();
}
}
}
}
List <RecommendedItem> result = new List <RecommendedItem>(topItems.Count);
foreach (RecommendedItem item in topItems)
{
result.Add(item);
}
return(result);
}