org.apache.mahout.cf.taste.impl.recommender.AllUnknownItemsCandidateItemsStrategy 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.apache.mahout.cf.taste.impl.recommender;

import org.apache.mahout.cf.taste.common.TasteException;
import org.apache.mahout.cf.taste.impl.common.FastIDSet;
import org.apache.mahout.cf.taste.impl.common.LongPrimitiveIterator;
import org.apache.mahout.cf.taste.model.DataModel;

public final class AllUnknownItemsCandidateItemsStrategy extends AbstractCandidateItemsStrategy {

  /** return all items the user has not yet seen */
  @Override
  protected FastIDSet doGetCandidateItems(long[] preferredItemIDs, DataModel dataModel, boolean includeKnownItems)
    throws TasteException {
    FastIDSet possibleItemIDs = new FastIDSet(dataModel.getNumItems());
    LongPrimitiveIterator allItemIDs = dataModel.getItemIDs();
    while (allItemIDs.hasNext()) {
      possibleItemIDs.add(allItemIDs.nextLong());
    }
    if (!includeKnownItems) {
      possibleItemIDs.removeAll(preferredItemIDs);
    }
    return possibleItemIDs;
  }
}