org.codelibs.elasticsearch.taste.model.GenericUserPreferenceArray Maven / Gradle / Ivy
/**
* 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.codelibs.elasticsearch.taste.model;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import org.codelibs.elasticsearch.taste.common.iterator.CountingIterator;
import com.google.common.base.Function;
import com.google.common.collect.Iterators;
/**
*
* Like {@link GenericItemPreferenceArray} but stores preferences for one user (all user IDs the same) rather
* than one item.
*
*
*
* This implementation maintains two parallel arrays, of item IDs and values. The idea is to save allocating
* {@link Preference} objects themselves. This saves the overhead of {@link Preference} objects but also
* duplicating the user ID value.
*
*
* @see BooleanUserPreferenceArray
* @see GenericItemPreferenceArray
* @see GenericPreference
*/
public final class GenericUserPreferenceArray implements PreferenceArray {
/**
*
*/
private static final long serialVersionUID = 1L;
private static final int ITEM = 1;
private static final int VALUE = 2;
private static final int VALUE_REVERSED = 3;
private final long[] ids;
private long id;
private final float[] values;
public GenericUserPreferenceArray(final int size) {
ids = new long[size];
values = new float[size];
id = Long.MIN_VALUE; // as a sort of 'unspecified' value
}
public GenericUserPreferenceArray(final List prefs) {
this(prefs.size());
final int size = prefs.size();
long userID = Long.MIN_VALUE;
for (int i = 0; i < size; i++) {
final Preference pref = prefs.get(i);
if (i == 0) {
userID = pref.getUserID();
} else {
if (userID != pref.getUserID()) {
throw new IllegalArgumentException(
"Not all user IDs are the same");
}
}
ids[i] = pref.getItemID();
values[i] = pref.getValue();
}
id = userID;
}
/**
* This is a private copy constructor for clone().
*/
private GenericUserPreferenceArray(final long[] ids, final long id,
final float[] values) {
this.ids = ids;
this.id = id;
this.values = values;
}
@Override
public int length() {
return ids.length;
}
@Override
public Preference get(final int i) {
return new PreferenceView(i);
}
@Override
public void set(final int i, final Preference pref) {
id = pref.getUserID();
ids[i] = pref.getItemID();
values[i] = pref.getValue();
}
@Override
public long getUserID(final int i) {
return id;
}
/**
* {@inheritDoc}
*
* Note that this method will actually set the user ID for all preferences.
*/
@Override
public void setUserID(final int i, final long userID) {
id = userID;
}
@Override
public long getItemID(final int i) {
return ids[i];
}
@Override
public void setItemID(final int i, final long itemID) {
ids[i] = itemID;
}
/**
* @return all item IDs
*/
@Override
public long[] getIDs() {
return ids;
}
@Override
public float getValue(final int i) {
return values[i];
}
@Override
public void setValue(final int i, final float value) {
values[i] = value;
}
@Override
public void sortByUser() {
}
@Override
public void sortByItem() {
lateralSort(ITEM);
}
@Override
public void sortByValue() {
lateralSort(VALUE);
}
@Override
public void sortByValueReversed() {
lateralSort(VALUE_REVERSED);
}
@Override
public boolean hasPrefWithUserID(final long userID) {
return id == userID;
}
@Override
public boolean hasPrefWithItemID(final long itemID) {
for (final long id : ids) {
if (itemID == id) {
return true;
}
}
return false;
}
private void lateralSort(final int type) {
//Comb sort: http://en.wikipedia.org/wiki/Comb_sort
final int length = length();
int gap = length;
boolean swapped = false;
while (gap > 1 || swapped) {
if (gap > 1) {
gap /= 1.247330950103979; // = 1 / (1 - 1/e^phi)
}
swapped = false;
final int max = length - gap;
for (int i = 0; i < max; i++) {
final int other = i + gap;
if (isLess(other, i, type)) {
swap(i, other);
swapped = true;
}
}
}
}
private boolean isLess(final int i, final int j, final int type) {
switch (type) {
case ITEM:
return ids[i] < ids[j];
case VALUE:
return values[i] < values[j];
case VALUE_REVERSED:
return values[i] > values[j];
default:
throw new IllegalStateException();
}
}
private void swap(final int i, final int j) {
final long temp1 = ids[i];
final float temp2 = values[i];
ids[i] = ids[j];
values[i] = values[j];
ids[j] = temp1;
values[j] = temp2;
}
@Override
public GenericUserPreferenceArray clone() {
return new GenericUserPreferenceArray(ids.clone(), id, values.clone());
}
@Override
public int hashCode() {
return (int) (id >> 32) ^ (int) id ^ Arrays.hashCode(ids)
^ Arrays.hashCode(values);
}
@Override
public boolean equals(final Object other) {
if (!(other instanceof GenericUserPreferenceArray)) {
return false;
}
final GenericUserPreferenceArray otherArray = (GenericUserPreferenceArray) other;
return id == otherArray.id && Arrays.equals(ids, otherArray.ids)
&& Arrays.equals(values, otherArray.values);
}
@Override
public Iterator iterator() {
return Iterators.transform(new CountingIterator(length()),
new Function() {
@Override
public Preference apply(final Integer from) {
return new PreferenceView(from);
}
});
}
@Override
public String toString() {
if (ids == null || ids.length == 0) {
return "GenericUserPreferenceArray[{}]";
}
final StringBuilder result = new StringBuilder(20 * ids.length);
result.append("GenericUserPreferenceArray[userID:");
result.append(id);
result.append(",{");
for (int i = 0; i < ids.length; i++) {
if (i > 0) {
result.append(',');
}
result.append(ids[i]);
result.append('=');
result.append(values[i]);
}
result.append("}]");
return result.toString();
}
private final class PreferenceView implements Preference {
private final int i;
private PreferenceView(final int i) {
this.i = i;
}
@Override
public long getUserID() {
return GenericUserPreferenceArray.this.getUserID(i);
}
@Override
public long getItemID() {
return GenericUserPreferenceArray.this.getItemID(i);
}
@Override
public float getValue() {
return values[i];
}
@Override
public void setValue(final float value) {
values[i] = value;
}
}
}