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[Mahout-1958] Change the variable type to long to avoid overflow #444

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[Mahout-1958] Change the variable type to long to avoid overflow #444

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16 changes: 8 additions & 8 deletions ...t-mr/mr/src/main/java/org/apache/mahout/cf/taste/impl/similarity/CityBlockSimilarity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -53,20 +53,20 @@ public void refresh(Collection<Refreshable> alreadyRefreshed) {
@Override
public double itemSimilarity(long itemID1, long itemID2) throws TasteException {
DataModel dataModel = getDataModel();
int preferring1 = dataModel.getNumUsersWithPreferenceFor(itemID1);
int preferring2 = dataModel.getNumUsersWithPreferenceFor(itemID2);
int intersection = dataModel.getNumUsersWithPreferenceFor(itemID1, itemID2);
long preferring1 = dataModel.getNumUsersWithPreferenceFor(itemID1);
long preferring2 = dataModel.getNumUsersWithPreferenceFor(itemID2);
long intersection = dataModel.getNumUsersWithPreferenceFor(itemID1, itemID2);
return doSimilarity(preferring1, preferring2, intersection);
}

@Override
public double[] itemSimilarities(long itemID1, long[] itemID2s) throws TasteException {
DataModel dataModel = getDataModel();
int preferring1 = dataModel.getNumUsersWithPreferenceFor(itemID1);
long preferring1 = dataModel.getNumUsersWithPreferenceFor(itemID1);
double[] distance = new double[itemID2s.length];
for (int i = 0; i < itemID2s.length; ++i) {
int preferring2 = dataModel.getNumUsersWithPreferenceFor(itemID2s[i]);
int intersection = dataModel.getNumUsersWithPreferenceFor(itemID1, itemID2s[i]);
long preferring2 = dataModel.getNumUsersWithPreferenceFor(itemID2s[i]);
long intersection = dataModel.getNumUsersWithPreferenceFor(itemID1, itemID2s[i]);
distance[i] = doSimilarity(preferring1, preferring2, intersection);
}
return distance;
Expand All @@ -90,8 +90,8 @@ public double userSimilarity(long userID1, long userID2) throws TasteException {
* @param pref2 number of non-zero values in right vector
* @param intersection number of overlapping non-zero values
*/
private static double doSimilarity(int pref1, int pref2, int intersection) {
int distance = pref1 + pref2 - 2 * intersection;
private static double doSimilarity(long pref1, long pref2, long intersection) {
long distance = pref1 + pref2 - 2 * intersection;
return 1.0 / (1.0 + distance);
}

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