protected FastIDSet doGetCandidateItems(long[] preferredItemIDs, DataModel dataModel) throws TasteException {
		int maxPrefsPerItemConsidered = (int) Math.min(defaultMaxPrefsPerItemConsidered, userItemCountMultiplier * Math.log(Math.max(dataModel.getNumUsers(), dataModel.getNumItems())));
		FastIDSet possibleItemsIDs = new FastIDSet();

		for (long itemID : preferredItemIDs) {
			
			PreferenceArray prefs = dataModel.getPreferencesForItem(itemID);
			int prefsConsidered = Math.min(prefs.length(), maxPrefsPerItemConsidered);
			Iterator<Preference> sampledPrefs = new FixedSizeSamplingIterator<Preference>(prefsConsidered, prefs.iterator());
			while (sampledPrefs.hasNext()) {
				possibleItemsIDs.addAll(dataModel.getItemIDsFromUser(sampledPrefs.next().getUserID()));
			}
		} 
		possibleItemsIDs.removeAll(preferredItemIDs);
	    
		//
		if (this.maxSampledItems > 0) {
			FastIDSet finalPossibleItemsIDs = new FastIDSet();
			Iterator<Long> sampledPossibleIDs = new FixedSizeSamplingIterator<Long>(this.maxSampledItems, possibleItemsIDs.iterator());
			while (sampledPossibleIDs.hasNext()) {
				finalPossibleItemsIDs.add(sampledPossibleIDs.next().longValue());
			}
			
			logger.debug("finalPossibleItemsIDs size:" + finalPossibleItemsIDs.size());
			
			return finalPossibleItemsIDs;
		}
		
		logger.debug("possibleItemsIDs size:" + possibleItemsIDs.size());
		return possibleItemsIDs;