/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.mahout.cf.taste.impl.model;
import org.apache.mahout.cf.taste.common.NoSuchItemException;
import org.apache.mahout.cf.taste.common.NoSuchUserException;
import org.apache.mahout.cf.taste.common.Refreshable;
import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastByIDMap;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.impl.common.LongPrimitiveArrayIterator;
import org.apache.mahout.cf.taste.impl.common.LongPrimitiveIterator;
import org.apache.mahout.cf.taste.model.DataModel;
import org.apache.mahout.cf.taste.model.PreferenceArray;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;
import java.util.List;
import java.util.Map;
/**
* <p>A simple {@link DataModel} which uses a given {@link List} of users as its data source. This
* implementation is mostly useful for small experiments and is not recommended for contexts where performance is
* important.</p>
*/
public final class GenericBooleanPrefDataModel implements DataModel, Serializable {
private final long[] userIDs;
private final FastByIDMap<FastIDSet> preferenceFromUsers;
private final long[] itemIDs;
private final FastByIDMap<FastIDSet> preferenceForItems;
/**
* <p>Creates a new {@link GenericDataModel} from the given users (and their preferences). This {@link
* DataModel} retains all this information in memory and is effectively immutable.</p>
*
* @param userData users to include
*/
@SuppressWarnings("unchecked")
public GenericBooleanPrefDataModel(FastByIDMap<FastIDSet> userData) {
if (userData == null) {
throw new IllegalArgumentException("userData is null");
}
this.preferenceFromUsers = userData;
this.preferenceForItems = new FastByIDMap<FastIDSet>();
FastIDSet itemIDSet = new FastIDSet();
for (Map.Entry<Long, FastIDSet> entry : preferenceFromUsers.entrySet()) {
long userID = entry.getKey();
FastIDSet itemIDs = entry.getValue();
itemIDSet.addAll(itemIDs);
LongPrimitiveIterator it = itemIDs.iterator();
while (it.hasNext()) {
long itemID = it.next();
FastIDSet userIDs = preferenceForItems.get(itemID);
if (userIDs == null) {
userIDs = new FastIDSet(2);
preferenceForItems.put(itemID, userIDs);
}
userIDs.add(userID);
}
}
this.itemIDs = itemIDSet.toArray();
itemIDSet = null; // Might help GC -- this is big
Arrays.sort(itemIDs);
this.userIDs = new long[userData.size()];
int i = 0;
LongPrimitiveIterator it = userData.keySetIterator();
while (it.hasNext()) {
userIDs[i++] = it.next();
}
Arrays.sort(userIDs);
}
/**
* <p>Creates a new {@link GenericDataModel} containing an immutable copy of the data from another given {@link
* DataModel}.</p>
*
* @param dataModel {@link DataModel} to copy
* @throws TasteException if an error occurs while retrieving the other {@link DataModel}'s users
*/
public GenericBooleanPrefDataModel(DataModel dataModel) throws TasteException {
this(toDataMap(dataModel));
}
private static FastByIDMap<FastIDSet> toDataMap(DataModel dataModel) throws TasteException {
FastByIDMap<FastIDSet> data = new FastByIDMap<FastIDSet>(dataModel.getNumUsers());
LongPrimitiveIterator it = dataModel.getUserIDs();
while (it.hasNext()) {
long userID = it.nextLong();
data.put(userID, dataModel.getItemIDsFromUser(userID));
}
return data;
}
public static FastByIDMap<FastIDSet> toDataMap(FastByIDMap<PreferenceArray> data) {
for (Map.Entry<Long, Object> entry : ((FastByIDMap<Object>) (FastByIDMap<?>) data).entrySet()) {
PreferenceArray prefArray = (PreferenceArray) entry.getValue();
int size = prefArray.length();
FastIDSet itemIDs = new FastIDSet(size);
for (int i = 0; i < size; i++) {
itemIDs.add(prefArray.getItemID(i));
}
entry.setValue(itemIDs);
}
return (FastByIDMap<FastIDSet>) (FastByIDMap<?>) data;
}
@Override
public LongPrimitiveArrayIterator getUserIDs() {
return new LongPrimitiveArrayIterator(userIDs);
}
/** @throws NoSuchUserException if there is no such user */
@Override
public PreferenceArray getPreferencesFromUser(long userID) throws NoSuchUserException {
FastIDSet itemIDs = preferenceFromUsers.get(userID);
if (itemIDs == null) {
throw new NoSuchUserException();
}
PreferenceArray prefArray = new BooleanUserPreferenceArray(itemIDs.size());
int i = 0;
LongPrimitiveIterator it = itemIDs.iterator();
while (it.hasNext()) {
prefArray.setUserID(i, userID);
prefArray.setItemID(i, it.next());
i++;
}
return prefArray;
}
@Override
public FastIDSet getItemIDsFromUser(long userID) throws TasteException {
FastIDSet itemIDs = preferenceFromUsers.get(userID);
if (itemIDs == null) {
throw new NoSuchUserException();
}
return itemIDs;
}
@Override
public LongPrimitiveArrayIterator getItemIDs() {
return new LongPrimitiveArrayIterator(itemIDs);
}
@Override
public PreferenceArray getPreferencesForItem(long itemID) throws NoSuchItemException {
FastIDSet userIDs = preferenceForItems.get(itemID);
if (userIDs == null) {
throw new NoSuchItemException();
}
PreferenceArray prefArray = new BooleanItemPreferenceArray(userIDs.size());
int i = 0;
LongPrimitiveIterator it = userIDs.iterator();
while (it.hasNext()) {
prefArray.setUserID(i, it.next());
prefArray.setItemID(i, itemID);
i++;
}
return prefArray;
}
@Override
public Float getPreferenceValue(long userID, long itemID) throws NoSuchUserException {
FastIDSet itemIDs = preferenceFromUsers.get(userID);
if (itemIDs == null) {
throw new NoSuchUserException();
}
if (itemIDs.contains(itemID)) {
return 1.0f;
}
return null;
}
@Override
public int getNumItems() {
return itemIDs.length;
}
@Override
public int getNumUsers() {
return userIDs.length;
}
@Override
public int getNumUsersWithPreferenceFor(long... itemIDs) throws NoSuchItemException {
if (itemIDs.length == 0) {
return 0;
}
FastIDSet userIDs = preferenceForItems.get(itemIDs[0]);
if (userIDs == null) {
throw new NoSuchItemException();
}
FastIDSet intersection = new FastIDSet(userIDs.size());
intersection.addAll(userIDs);
int i = 1;
while (!intersection.isEmpty() && i < itemIDs.length) {
userIDs = preferenceForItems.get(itemIDs[i]);
if (userIDs == null) {
throw new NoSuchItemException();
}
intersection.retainAll(userIDs);
i++;
}
return intersection.size();
}
@Override
public void removePreference(long userID, long itemID) {
throw new UnsupportedOperationException();
}
@Override
public void setPreference(long userID, long itemID, float value) {
throw new UnsupportedOperationException();
}
@Override
public void refresh(Collection<Refreshable> alreadyRefreshed) {
// Does nothing
}
@Override
public String toString() {
StringBuilder result = new StringBuilder(200);
result.append("GenericBooleanPrefDataModel[users:");
for (int i = 0; i < Math.min(3, userIDs.length); i++) {
if (i > 0) {
result.append(',');
}
result.append(userIDs[i]);
}
if (result.length() > 3) {
result.append("...");
}
result.append(']');
return result.toString();
}
}