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From: Stefan Bodewig <bodewig@apache.org>
To: dev@ant.apache.org
Subject: Re: Bug 50200, VectorSet kills the performance of DirectoryScanner
References: <4D056C68.3060705@gmx.de>
Date: Mon, 13 Dec 2010 10:15:43 +0100
In-Reply-To: <4D056C68.3060705@gmx.de> (Antoine Levy-Lambert's message of
	"Sun, 12 Dec 2010 19:44:24 -0500")
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On 2010-12-13, Antoine Levy-Lambert wrote:

> Hi,

> I got a private email asking me to apply the patch suggested by
> *Bug 50200* <https://issues.apache.org/bugzilla/show_bug.cgi?id=50200> - [1]
>       VectorSet kills the performance of DirectoryScanner

> The code looks good and I am wondering why we have the current implementation.

> Stefan ?

I remember I looked at the patch a few weeks ago but ran out of time
back then.

The reason I didn't commit it right away is that at first glance it
seems to make assumptions about the base class's implementation that may
or may not be true.  At first first I thought that if Vector#add(Object)
delegates to Vector#add(int,Object) the suggested implementation would
lead to an infinite loop.  Now I see this is not true because the set
will contain the object on the second invocation of doAdd - but this
also means if the base class's add does indeed delegate the way I
described then the object is not going to be added to the Vector at all.

So all in all I still feel the patch relies on undocumented details of
Vector's implementation and am not I sure when I'll find time to verify
or falsify that feeling.  It may be easier to avoid the arraycopy for
the index==size() case without invoking any base methods anyway.

I'll comment on the bug report directly so you don't have to relay
between the bug reporter and this list.

Stefan

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