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Date: Fri, 18 Apr 2008 11:55:48 -0500
From: "Nathan Beyer" <ndbeyer@apache.org>
Sender: nbeyer@gmail.com
To: dev@harmony.apache.org
Subject: Re: [classlib][luni][performance] Improvements in Collections
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I know that people will notice; I have personal experience with systems that
included custom Map implementations were written because HashMaps grew too
large for small data sets (less than 2000, actually) and wasted a lot of
memory for the unnecessary capacity. Even the use of the capacity and load
factor didn't provide enough compensation in these cases.

-Nathan

On Fri, Apr 18, 2008 at 11:46 AM, Sergey Salishev <
sergey.i.salishev@gmail.com> wrote:

> Nathan,
>
> I don't think anyone will notice the hash map size rounding. It can lead
> to
> some memory overhead in very rare cases the user creates hash map with the
> exact size. But in the most common case where the map is created with
> default size the rounding will not change the behavior at all as it's in
> agreement with the standard 2x growth policy. On the other hand size
> rounding gives substantial performance boost on all gets.
>
> Thanks.
> Sergey.
>
>
> On Fri, Apr 18, 2008 at 8:13 PM, Nathan Beyer <ndbeyer@apache.org<https://mail.google.com/mail?view=cm&tf=0&to=ndbeyer@apache.org>>
> wrote:
>
> > https://issues.apache.org/jira/browse/HARMONY-5718
> >
> > Again, I don't agree with the capacity rounding in the patch attached to
> > this issue. I do like the change to the internal data structure; use two
> > arrays for key/value instead a single array. It makes the code easier to
> > read.
> >
> > -Nathan
> >
> > On Fri, Apr 18, 2008 at 1:50 AM, Aleksey Shipilev <
> > aleksey.shipilev@gmail.com<https://mail.google.com/mail?view=cm&tf=0&to=aleksey.shipilev@gmail.com>>
> wrote:
> >
> >  > Colleagues,
> > >
> > > I had recently filed two JIRAs with improvements in Collections,
> > > giving up to +30-40% to serialization benchmarks. Presumably they will
> > > boost the performance across the all users since the optimization is
> > > pretty general:
> > > https://issues.apache.org/jira/browse/HARMONY-5761
> > > https://issues.apache.org/jira/browse/HARMONY-5718
> > >
> > > Would some classlib guru (Tim, Nathan, Tony?) review and commit them?
> > >
> > > Thanks,
> > > Aleksey.
> > >
> >
>

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