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From "Simone Tripodi (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SANDBOX-341) [functor] New components: summarize and aggregate
Date Mon, 12 Sep 2011 06:47:08 GMT

    [ https://issues.apache.org/jira/browse/SANDBOX-341?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13102461#comment-13102461
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Simone Tripodi commented on SANDBOX-341:
----------------------------------------

I had a look at the new patch, few more minor comments:

 * since {{Aggregator<T>}} now extends {{Function<T>}}, there's no need to redeclare
the {{T evaluate()}} method;
 * in abstract implementations, Class members access has to be done via getters/setters instead
of making fields protected (checkstyle would complain about it)

Moreover, a favor: can you please create a documentation page under {{src/site/xdoc/}}? That
would be useful to put users aware of such feature (and yes, the rest of documentation is
still a TODO :P)

Many thanks in advance for your hard work!

> [functor] New components: summarize and aggregate
> -------------------------------------------------
>
>                 Key: SANDBOX-341
>                 URL: https://issues.apache.org/jira/browse/SANDBOX-341
>             Project: Commons Sandbox
>          Issue Type: Improvement
>          Components: Functor
>         Environment: JDK 1.6.0_25 but should work with any JDK 5+ (possibly 1.4 though
I haven't tested).
>            Reporter: Liviu Tudor
>            Priority: Minor
>              Labels: features
>         Attachments: commons-functor-aggregate+summarizer.zip, commons-functor.patch.bz2
>
>
> This is the next step from https://issues.apache.org/jira/browse/SANDBOX-340 -- as instructed
I'm finally hoping to get the code in the right place and hopefully this is something that
the functor component could do with.
> Whereas initially I just started with the summarizer component, I have added now the
second one, the "aggregator" as they are somehow related. If this code proves to be useful
to functor in any way, it would actually be good to get some feedback on these 2 to see if
the class hierarchy can in fact be changed to share some common functionality as I feel (probably
due to the similar needs that lead to writing/using these components) that somehow they should
share a common base.
> In brief, the 2 components:
> * aggregator: this just allows for data to be aggregated in a user defined way (e.g.
stored in a list for the purpose of averaging, computing the arithmetic median etc). The classes
provided actually offer the implementation for storing data in a list and computing the above-mentioned
values or summing up everything.
> * timed summarizer: this is another variation of the aggreator, however, it adds the
idea of regular "flushes", so based on a timer it will reset the value and start summing/aggregating
the data again. Rather than using an aggregator which would store the whole data series (possibly
for applying more complex formulas), this component just computes on the fly on each request
the formula and stores the result of it. (Which does mean things like computing arithmetic
mean, median etc would be difficult to compute without knowing upfront how many calls will
be received -- i.e. how many elements we will be required to summarize/aggregate.) So the
memory footprint of running this is much smaller -- even though, as I said, it achieves similar
results. I have only provided a summarizer which operates on integers, but obviously others
for float, double etc can be created if we go ahead with this design.
> Hopefully the above make sense; this code has resulted from finding myself writing similar
components to these a few times and because it's always been either one type (e.g. aggregator)
or another (summarizer) I haven't given quite possibly enough thought to the class design
to join these 2. Also, unfortunately, the time I sat down to make these components a bit more
general and submitted issue 340 was nearly 3 months ago so I'm trying to remember myself all
the ideas I had at a time so bear with me please if these are still  a bit fuzzy :) However,
if you can make use of these I'm quite happy to elaborate on areas that are unclear and obviously
put some effort into getting these components to the standards required to put these into
a release.

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