[jira] [Commented] (COLLECTIONS-413) Performance problem in DualHashBidiMap

["Hudson (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/COLLECTIONS-413?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13399932#comment-13399932 ] 

Hudson commented on COLLECTIONS-413:
------------------------------------

Integrated in commons-collections #30 (See [https://builds.apache.org/job/commons-collections/30/])
    [COLLECTIONS-413] Improve performance of DualBidiMap#removeAll. Thanks to Adrian Nistor for report and patch. (Revision 1353115)

     Result = SUCCESS
tn : http://svn.apache.org/viewvc/?view=rev&rev=1353115
Files : 
* /commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/bidimap/AbstractDualBidiMap.java

                
> Performance problem in DualHashBidiMap
> --------------------------------------
>
>                 Key: COLLECTIONS-413
>                 URL: https://issues.apache.org/jira/browse/COLLECTIONS-413
>             Project: Commons Collections
>          Issue Type: Bug
>    Affects Versions: 3.2.1
>         Environment: java 1.6.0_24
> Ubuntu 11.10
>            Reporter: Adrian Nistor
>             Fix For: 4.0
>
>         Attachments: Test.java, removeAll.diff
>
>
> Hi,
> I am encountering a performance problem in DualHashBidiMap.  It
> appears in version 3.2.1 and also in revision 1352574 (21 June 2012).
> I attached a test that exposes this problem and a patch that fixes it.
> On my machine, for this test, the patch provides a 173X speedup.
> To run the test, just do:
> $ java Test
> The output for the un-patched version is:
> Time is 5029
> The output for the patched version is:
> Time is 29
> The attached test shows that, for a "DualHashBidiMap bidi" object, the
> following operation is very slow:
> bidi.entrySet().removeAll(toRemove);
> DualHashBidiMap.entrySet() returns a
> "DualHashBidiMap.EntrySet" object, which inherits 
> removeAll(Collection<?> coll) from "DualHashBidiMap.View".  
> As the patch shows, the problem is that
> "DualHashBidiMap.View.removeAll(Collection<?> coll)" performs
> "coll.contains(it.next())" for each element in the View.
> "coll.contains(it.next())" can be very slow, e.g., if "coll" is a
> list.
> The patch avoids this cost by using remove(Object obj) (defined in
> "EntrySet<K, V>", "KeySet<K>", and "Values<V>"), which is fast because
> it uses only operations on sets.
> Is this a bug, or am I misunderstanding something? If so, can you
> please confirm that the patch is correct?
> Thanks,
> Adrian

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