[jira] Commented: (MAHOUT-186) Classifier PriorityQueue returns erroneous results

[Ted Dunning (JIRA)]

    [ 
https://issues.apache.org/jira/browse/MAHOUT-186?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12763172#action_12763172
 ] 

Ted Dunning commented on MAHOUT-186:
------------------------------------

You are right that I should code up an example before speaking.  But it does 
seem that, against all odds, that what I was suggesting works.

Here is a test case that illustrates what I meant.  I am still not sure what 
everybody is saying:

{noformat}
package com.infovell.logging.test;

import junit.framework.TestCase;

import java.util.PriorityQueue;
import java.util.Random;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;

public class FooTest extends TestCase {
    public void testQueue() {
        PriorityQueue<Double> pq = new PriorityQueue<Double>(10);
        Random gen = new Random(123L);
        for (int i = 0; i < 1000; i++) {
            double x = gen.nextDouble();
            if (pq.size() < 10 || x > pq.peek()) {
                pq.add(x);
                while (pq.size() > 10) {
                    pq.remove();
                }
            }
        }

        List<Double> r = new ArrayList<Double>(pq);
        Collections.reverse(r);
        System.out.printf("%s\n", r);
        assertEquals(0.994991252160446, r.get(0), 1e-7);
        assertEquals(0.9881699208527764, r.get(9), 1e-7);
    }
}
{noformat}

> Classifier PriorityQueue returns erroneous results
> --------------------------------------------------
>
>                 Key: MAHOUT-186
>                 URL: https://issues.apache.org/jira/browse/MAHOUT-186
>             Project: Mahout
>          Issue Type: Bug
>    Affects Versions: 0.1, 0.2
>            Reporter: Robin Anil
>            Assignee: Robin Anil
>             Fix For: 0.2
>
>         Attachments: MAHOUT-186.patch
>
>
> A simple test fails 
> import org.apache.hadoop.util.PriorityQueue;
> PriorityQueue<ClassifierResult> queue = new ClassifierResultPriorityQueue(3);
>     queue.insert(new ClassifierResult("label1", 5));
>     queue.insert(new ClassifierResult("label2", 4));
>     queue.insert(new ClassifierResult("label3", 3));
>     queue.insert(new ClassifierResult("label4", 2));
>     queue.insert(new ClassifierResult("label5", 1));
>     
>     assertEquals("Incorrect Size", 3, queue.size());
>     log.info(queue.pop().toString());
>     log.info(queue.pop().toString());
>     log.info(queue.pop().toString());
> 09/10/07 16:58:39 INFO common.ClassifierResultPriorityQueueTest: 
> ClassifierResult{category='label3', score=3.0}
> 09/10/07 16:58:39 INFO common.ClassifierResultPriorityQueueTest: 
> ClassifierResult{category='label4', score=2.0}
> 09/10/07 16:58:39 INFO common.ClassifierResultPriorityQueueTest: 
> ClassifierResult{category='label5', score=1.0}
> Expected label1 and label2 at the top

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.