/*
* Copyright (c) 2014, Cloudera and Intel, Inc. All Rights Reserved.
*
* Cloudera, Inc. 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
*
* This software 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 com.cloudera.oryx.ml.serving.als;
import java.util.List;
import javax.ws.rs.DefaultValue;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;
import com.carrotsearch.hppc.ObjectIntMap;
import com.carrotsearch.hppc.cursors.ObjectIntCursor;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.collect.Ordering;
import com.cloudera.oryx.common.collection.Pair;
import com.cloudera.oryx.common.collection.PairComparators;
import com.cloudera.oryx.ml.serving.CSVMessageBodyWriter;
import com.cloudera.oryx.ml.serving.IDCount;
import com.cloudera.oryx.ml.serving.als.model.ALSServingModel;
/**
* <p>Responds to a GET request to {@code /mostPopularItems(?howMany=n)(&offset=o)}
*
* <p>Results are items that the most users have interacted with, as item and count pairs.</p>
*
* <p>{@code howMany} and {@code offset} behavior are as in {@link Recommend}. Output
* is also the same, except that item IDs are returned with integer counts rather than
* scores.</p>
*/
@Path("/mostPopularItems")
public final class MostPopularItems extends AbstractALSResource {
@GET
@Produces({CSVMessageBodyWriter.TEXT_CSV, MediaType.APPLICATION_JSON})
public List<IDCount> get(@DefaultValue("10") @QueryParam("howMany") int howMany,
@DefaultValue("0") @QueryParam("offset") int offset) {
ALSServingModel model = getALSServingModel();
ObjectIntMap<String> itemCounts = model.getItemCounts();
Iterable<Pair<String,Integer>> countPairs =
Iterables.transform(itemCounts,
new Function<ObjectIntCursor<String>, Pair<String,Integer>>() {
@Override
public Pair<String,Integer> apply(ObjectIntCursor<String> input) {
return new Pair<>(input.key, input.value);
}
});
List<Pair<String,Integer>> allTopCountPairs =
Ordering.from(PairComparators.<Integer>bySecond()).greatestOf(countPairs, howMany + offset);
List<Pair<String,Integer>> topCountPairs =
selectedSublist(allTopCountPairs, howMany, offset);
return Lists.transform(topCountPairs,
new Function<Pair<String, Integer>, IDCount>() {
@Override
public IDCount apply(Pair<String,Integer> idCount) {
return new IDCount(idCount.getFirst(), idCount.getSecond());
}
});
}
}