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

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

     [ https://issues.apache.org/jira/browse/COLLECTIONS-413?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Thomas Neidhart resolved COLLECTIONS-413.
-----------------------------------------

       Resolution: Fixed
    Fix Version/s: 4.0

Applied patch in r1353115.

Thanks for reporting and providing a patch!
                
> 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

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators: https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira