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From "Yonik Seeley (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-693) ConjunctionScorer - more tuneup
Date Tue, 24 Oct 2006 14:18:17 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-693?page=comments#action_12444319 ] 
            
Yonik Seeley commented on LUCENE-693:
-------------------------------------

Thanks for trying it out Peter.
Odd it could fail after passing all the Lucene unit tests... I assume this was the lucene
trunk you were trying?
So the query was just a boolean query with three required term queries?

> ConjunctionScorer - more tuneup
> -------------------------------
>
>                 Key: LUCENE-693
>                 URL: http://issues.apache.org/jira/browse/LUCENE-693
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Search
>    Affects Versions: 2.1
>         Environment: Windows Server 2003 x64, Java 1.6, pretty large index
>            Reporter: Peter Keegan
>         Attachments: conjunction.patch
>
>
> (See also: #LUCENE-443)
> I did some profile testing with the new ConjuctionScorer in 2.1 and discovered a new
bottleneck in ConjunctionScorer.sortScorers. The java.utils.Arrays.sort method is cloning
the Scorers array on every sort, which is quite expensive on large indexes because of the
size of the 'norms' array within, and isn't necessary. 
> Here is one possible solution:
>   private void sortScorers() {
> // squeeze the array down for the sort
> //    if (length != scorers.length) {
> //      Scorer[] temps = new Scorer[length];
> //      System.arraycopy(scorers, 0, temps, 0, length);
> //      scorers = temps;
> //    }
>     insertionSort( scorers,length );
>     // note that this comparator is not consistent with equals!
> //    Arrays.sort(scorers, new Comparator() {         // sort the array
> //        public int compare(Object o1, Object o2) {
> //          return ((Scorer)o1).doc() - ((Scorer)o2).doc();
> //        }
> //      });
>   
>     first = 0;
>     last = length - 1;
>   }
>   private void insertionSort( Scorer[] scores, int len)
>   {
>       for (int i=0; i<len; i++) {
>           for (int j=i; j>0 && scores[j-1].doc() > scores[j].doc();j--
) {
>               swap (scores, j, j-1);
>           }
>       }
>       return;
>   }
>   private void swap(Object[] x, int a, int b) {
>     Object t = x[a];
>     x[a] = x[b];
>     x[b] = t;
>   }
>  
> The squeezing of the array is no longer needed. 
> We also initialized the Scorers array to 8 (instead of 2) to avoid having to grow the
array for common queries, although this probably has less performance impact.
> This change added about 3% to query throughput in my testing.
> Peter

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