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https://issues.apache.org/jira/browse/LUCENE-584?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12487594
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Yonik Seeley commented on LUCENE-584:
-------------------------------------
> When you rerun, you may want to use my alg - to compare the two approaches in
> one run.
This is more dangerous though. GC from one method's garbage can penalize the
2nd methods performance.
Also, hotspot effects are hard to account for (if method1 and method2 use
common methods, method2 will often execute faster than method one because more
optimization has been done on those common methods).
The hotspot effect can be minimized by running the test multiple times in the
same JVM instance and discarding the first runs, but it's not so easy for GC.
> Decouple Filter from BitSet
> ---------------------------
>
> Key: LUCENE-584
> URL: https://issues.apache.org/jira/browse/LUCENE-584
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Search
> Affects Versions: 2.0.1
> Reporter: Peter Schäfer
> Priority: Minor
> Attachments: bench-diff.txt, bench-diff.txt, BitsMatcher.java,
> Filter-20060628.patch, HitCollector-20060628.patch,
> IndexSearcher-20060628.patch, MatchCollector.java, Matcher.java,
> Matcher20070226.patch, Scorer-20060628.patch, Searchable-20060628.patch,
> Searcher-20060628.patch, Some Matchers.zip, SortedVIntList.java,
> TestSortedVIntList.java
>
>
> {code}
> package org.apache.lucene.search;
> public abstract class Filter implements java.io.Serializable
> {
> public abstract AbstractBitSet bits(IndexReader reader) throws IOException;
> }
> public interface AbstractBitSet
> {
> public boolean get(int index);
> }
> {code}
> It would be useful if the method =Filter.bits()= returned an abstract
> interface, instead of =java.util.BitSet=.
> Use case: there is a very large index, and, depending on the user's
> privileges, only a small portion of the index is actually visible.
> Sparsely populated =java.util.BitSet=s are not efficient and waste lots of
> memory. It would be desirable to have an alternative BitSet implementation
> with smaller memory footprint.
> Though it _is_ possibly to derive classes from =java.util.BitSet=, it was
> obviously not designed for that purpose.
> That's why I propose to use an interface instead. The default implementation
> could still delegate to =java.util.BitSet=.
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