private static IPreferenceArray cloneAndMergeInto(IPreferenceArray delegatePrefs,
long itemID,
long newUserID,
float value)
{
int length = delegatePrefs == null ? 0 : delegatePrefs.Length();
int newLength = length + 1;
IPreferenceArray newPreferenceArray = new GenericItemPreferenceArray(newLength);
// Set item ID once
newPreferenceArray.SetItemID(0, itemID);
int positionToInsert = 0;
while (positionToInsert < length && newUserID > delegatePrefs.GetUserID(positionToInsert))
{
positionToInsert++;
}
for (int i = 0; i < positionToInsert; i++)
{
newPreferenceArray.SetUserID(i, delegatePrefs.GetUserID(i));
newPreferenceArray.SetValue(i, delegatePrefs.GetValue(i));
}
newPreferenceArray.SetUserID(positionToInsert, newUserID);
newPreferenceArray.SetValue(positionToInsert, value);
for (int i = positionToInsert + 1; i < newLength; i++)
{
newPreferenceArray.SetUserID(i, delegatePrefs.GetUserID(i - 1));
newPreferenceArray.SetValue(i, delegatePrefs.GetValue(i - 1));
}
return(newPreferenceArray);
}
public override int GetNumUsersWithPreferenceFor(long itemID1, long itemID2)
{
IPreferenceArray prefs1 = preferenceForItems.Get(itemID1);
if (prefs1 == null)
{
return(0);
}
IPreferenceArray prefs2 = preferenceForItems.Get(itemID2);
if (prefs2 == null)
{
return(0);
}
int size1 = prefs1.Length();
int size2 = prefs2.Length();
int count = 0;
int i = 0;
int j = 0;
long userID1 = prefs1.GetUserID(0);
long userID2 = prefs2.GetUserID(0);
while (true)
{
if (userID1 < userID2)
{
if (++i == size1)
{
break;
}
userID1 = prefs1.GetUserID(i);
}
else if (userID1 > userID2)
{
if (++j == size2)
{
break;
}
userID2 = prefs2.GetUserID(j);
}
else
{
count++;
if (++i == size1 || ++j == size2)
{
break;
}
userID1 = prefs1.GetUserID(i);
userID2 = prefs2.GetUserID(j);
}
}
return(count);
}
public virtual IPreferenceArray GetPreferencesForItem(long itemID)
{
if (tempPrefs == null)
{
return(_delegate.GetPreferencesForItem(itemID));
}
IPreferenceArray delegatePrefs = null;
try {
delegatePrefs = _delegate.GetPreferencesForItem(itemID);
} catch (NoSuchItemException nsie) {
// OK. Probably an item that only the anonymous user has
//if (log.isDebugEnabled()) {
log.Debug("Item {} unknown", itemID);
//}
}
for (int i = 0; i < tempPrefs.Length(); i++)
{
if (tempPrefs.GetItemID(i) == itemID)
{
return(cloneAndMergeInto(delegatePrefs, itemID, tempPrefs.GetUserID(i), tempPrefs.GetValue(i)));
}
}
if (delegatePrefs == null)
{
// No, didn't find it among the anonymous user prefs
throw new NoSuchItemException(itemID);
}
return(delegatePrefs);
}
protected override FastIDSet doGetCandidateItems(long[] preferredItemIDs, IDataModel dataModel)
{
FastIDSet possibleItemsIDs = new FastIDSet();
foreach (long itemID in preferredItemIDs)
{
IPreferenceArray itemPreferences = dataModel.GetPreferencesForItem(itemID);
int numUsersPreferringItem = itemPreferences.Length();
for (int index = 0; index < numUsersPreferringItem; index++)
{
possibleItemsIDs.AddAll(dataModel.GetItemIDsFromUser(itemPreferences.GetUserID(index)));
}
}
possibleItemsIDs.RemoveAll(preferredItemIDs);
return(possibleItemsIDs);
}
protected override FastIDSet doGetCandidateItems(long[] preferredItemIDs, IDataModel dataModel)
{
var preferredItemIDsIterator = ((IEnumerable <long>)preferredItemIDs).GetEnumerator();
if (preferredItemIDs.Length > maxItems)
{
double samplingRate = (double)maxItems / preferredItemIDs.Length;
log.Info("preferredItemIDs.Length {0}, samplingRate {1}", preferredItemIDs.Length, samplingRate);
preferredItemIDsIterator =
new SamplinglongPrimitiveIterator(preferredItemIDsIterator, samplingRate);
}
FastIDSet possibleItemsIDs = new FastIDSet();
while (preferredItemIDsIterator.MoveNext())
{
long itemID = preferredItemIDsIterator.Current;
IPreferenceArray prefs = dataModel.GetPreferencesForItem(itemID);
int prefsLength = prefs.Length();
if (prefsLength > maxUsersPerItem)
{
var sampledPrefs =
new FixedSizeSamplingIterator <IPreference>(maxUsersPerItem, prefs.GetEnumerator());
while (sampledPrefs.MoveNext())
{
addSomeOf(possibleItemsIDs, dataModel.GetItemIDsFromUser(sampledPrefs.Current.GetUserID()));
}
}
else
{
for (int i = 0; i < prefsLength; i++)
{
addSomeOf(possibleItemsIDs, dataModel.GetItemIDsFromUser(prefs.GetUserID(i)));
}
}
}
possibleItemsIDs.RemoveAll(preferredItemIDs);
return(possibleItemsIDs);
}
public override double ItemSimilarity(long itemID1, long itemID2)
{
IDataModel dataModel = getDataModel();
IPreferenceArray xPrefs = dataModel.GetPreferencesForItem(itemID1);
IPreferenceArray yPrefs = dataModel.GetPreferencesForItem(itemID2);
int xLength = xPrefs.Length();
int yLength = yPrefs.Length();
if (xLength == 0 || yLength == 0)
{
return(Double.NaN);
}
long xIndex = xPrefs.GetUserID(0);
long yIndex = yPrefs.GetUserID(0);
int xPrefIndex = 0;
int yPrefIndex = 0;
double sumX = 0.0;
double sumX2 = 0.0;
double sumY = 0.0;
double sumY2 = 0.0;
double sumXY = 0.0;
double sumXYdiff2 = 0.0;
int count = 0;
// No, pref inferrers and transforms don't apply here. I think.
while (true)
{
int compare = xIndex <yIndex ? -1 : xIndex> yIndex ? 1 : 0;
if (compare == 0)
{
// Both users expressed a preference for the item
double x = xPrefs.GetValue(xPrefIndex);
double y = yPrefs.GetValue(yPrefIndex);
sumXY += x * y;
sumX += x;
sumX2 += x * x;
sumY += y;
sumY2 += y * y;
double diff = x - y;
sumXYdiff2 += diff * diff;
count++;
}
if (compare <= 0)
{
if (++xPrefIndex == xLength)
{
break;
}
xIndex = xPrefs.GetUserID(xPrefIndex);
}
if (compare >= 0)
{
if (++yPrefIndex == yLength)
{
break;
}
yIndex = yPrefs.GetUserID(yPrefIndex);
}
}
double result;
if (centerData)
{
// See comments above on these computations
double n = (double)count;
double meanX = sumX / n;
double meanY = sumY / n;
// double centeredSumXY = sumXY - meanY * sumX - meanX * sumY + n * meanX * meanY;
double centeredSumXY = sumXY - meanY * sumX;
// double centeredSumX2 = sumX2 - 2.0 * meanX * sumX + n * meanX * meanX;
double centeredSumX2 = sumX2 - meanX * sumX;
// double centeredSumY2 = sumY2 - 2.0 * meanY * sumY + n * meanY * meanY;
double centeredSumY2 = sumY2 - meanY * sumY;
result = computeResult(count, centeredSumXY, centeredSumX2, centeredSumY2, sumXYdiff2);
}
else
{
result = computeResult(count, sumXY, sumX2, sumY2, sumXYdiff2);
}
if (!Double.IsNaN(result))
{
result = normalizeWeightResult(result, count, cachedNumUsers);
}
return(result);
}
private static IPreferenceArray cloneAndMergeInto(IPreferenceArray delegatePrefs,
long itemID,
long newUserID,
float value) {
int length = delegatePrefs == null ? 0 : delegatePrefs.Length();
int newLength = length + 1;
IPreferenceArray newPreferenceArray = new GenericItemPreferenceArray(newLength);
// Set item ID once
newPreferenceArray.SetItemID(0, itemID);
int positionToInsert = 0;
while (positionToInsert < length && newUserID > delegatePrefs.GetUserID(positionToInsert)) {
positionToInsert++;
}
for (int i = 0; i < positionToInsert; i++) {
newPreferenceArray.SetUserID(i, delegatePrefs.GetUserID(i));
newPreferenceArray.SetValue(i, delegatePrefs.GetValue(i));
}
newPreferenceArray.SetUserID(positionToInsert, newUserID);
newPreferenceArray.SetValue(positionToInsert, value);
for (int i = positionToInsert + 1; i < newLength; i++) {
newPreferenceArray.SetUserID(i, delegatePrefs.GetUserID(i - 1));
newPreferenceArray.SetValue(i, delegatePrefs.GetValue(i - 1));
}
return newPreferenceArray;
}
