gistfile1.java

@Override
public SimpleItemItemModel get() {
    // Get the transposed rating matrix
    // This gives us a map of item IDs to those items' rating vectors
    Map<Long, ImmutableSparseVector> itemVectors = getItemVectors();

    // Get all items - you might find this useful
    LongSortedSet items = LongUtils.packedSet(itemVectors.keySet());

    // Map items to vectors of item similarities
//        Map<Long,MutableSparseVector> itemSimilarities = new HashMap<Long, MutableSparseVector>();
    Map<Long,List<ScoredId>> neighbours = new HashMap<Long, List<ScoredId>>();

    // TODO FIXED Compute the similarities between each pair of items

    CosineVectorSimilarity similarityObject = new CosineVectorSimilarity();

    for(long itemId: items) {
        TopNScoredItemAccumulator accumulator = new TopNScoredItemAccumulator(items.size() - 1);
        for(long otherItemId: items) {
            if(itemId != otherItemId) {
                double sim = similarityObject.similarity(itemVectors.get(itemId), itemVectors.get(otherItemId));
                if(sim >= 0) {
                    accumulator.put(otherItemId, sim);
                }
            }
        }
        List<ScoredId> similarities = accumulator.finish();
        neighbours.put(itemId, similarities);

    }

    // It will need to be in a map of longs to lists of Scored IDs to store in the model
//        return new SimpleItemItemModel(Collections.EMPTY_MAP);
    return new SimpleItemItemModel(neighbours);
}