net.myrrix.common

Class TopN

java.lang.Object

net.myrrix.common.TopN

public final class TopN
extends Object

Utility methods for finding the top N things from a stream.

Author:

Sean Owen, Mahout

Method Summary

Methods

Modifier and Type	Method and Description
static Queue<MutableRecommendedItem>	initialQueue(int n)
static List<org.apache.mahout.cf.taste.recommender.RecommendedItem>	selectTopN(Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values, int n)
static List<org.apache.mahout.cf.taste.recommender.RecommendedItem>	selectTopNFromQueue(Queue<MutableRecommendedItem> topN, int n)
static void	selectTopNIntoQueue(Queue<MutableRecommendedItem> topN, Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values, int n) Computes top N values for a stream and puts them into a Queue.
static void	selectTopNIntoQueueMultithreaded(Queue<MutableRecommendedItem> topN, float[] queueLeastValue, Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values, int n) Computes top N values for a stream and puts them into a Queue.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

initialQueue

public static Queue<MutableRecommendedItem> initialQueue(int n)

Parameters:

n - how many top values to choose

Returns:

Initialized Queue suitable for use in this class

selectTopNIntoQueue

public static void selectTopNIntoQueue(Queue<MutableRecommendedItem> topN,
                       Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values,
                       int n)

Computes top N values for a stream and puts them into a Queue.

Parameters:

topN - Queue to add to

values - stream of values from which to choose

n - how many top values to choose

selectTopNIntoQueueMultithreaded

public static void selectTopNIntoQueueMultithreaded(Queue<MutableRecommendedItem> topN,
                                    float[] queueLeastValue,
                                    Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values,
                                    int n)

Computes top N values for a stream and puts them into a Queue. Used in the context of multiple threads.

Parameters:

topN - Queue to add to

queueLeastValue - in/out parameter caching the queue's least value

values - stream of values from which to choose

n - how many top values to choose

selectTopNFromQueue

public static List<org.apache.mahout.cf.taste.recommender.RecommendedItem> selectTopNFromQueue(Queue<MutableRecommendedItem> topN,
                                                                               int n)

Parameters:

topN - Queue of items from which to take top n

n - how many top values to choose

Returns:

order list of top results

selectTopN

public static List<org.apache.mahout.cf.taste.recommender.RecommendedItem> selectTopN(Iterator<org.apache.mahout.cf.taste.recommender.RecommendedItem> values,
                                                                      int n)

Parameters:

values - stream of values from which to choose

n - how many top values to choose

Returns:

the top N values (at most), ordered by value descending.