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List: kde-panel-devel
Subject: Re: Review Request 108992: Simple optimizations in SignalPlotter
From: "Aaron J. Seigo" <aseigo () kde ! org>
Date: 2013-02-26 12:50:20
Message-ID: 20130226125020.27505.85710 () vidsolbach ! de
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> On Feb. 22, 2013, 1:32 a.m., Aaron J. Seigo wrote:
> > plasma/widgets/signalplotter.cpp, line 230
> > <http://git.reviewboard.kde.org/r/108992/diff/1/?file=114209#file114209line230>
> >
> > no point in taking PODs out of the loop
>
> Raul Fernandes wrote:
> Actually, the benefit exists in PODs too (the compiler has to adjust the stack each \
> iteration) but is minor. I agree. I don't agree that it uglifies the code or make \
> it less readable. To me, it doesn't make any difference to readability and has the \
> (little) gain in performance. My opinion.
So we have a difference in opinion when it comes to readability, and that's what it \
is: an opinion. As the maintainer, my opinion wins in a tie :) My reason for this is \
that we end up with more variables outside the scope they are used which means to \
understand the loop one needs to read more outside the loop, and should other \
variables of similar name appear later on .....
PODs have very, very little overhead and we value the readability over such \
micro-optimizations. to confirm this with actual numbers i wrote a small test program \
that interates 10 million times performing simple math on 6 ints that are declared in \
the loop or out of it. result? neither exceeded 1ms. so in this case, it is not worth \
it.
Conclusion: PODs will remain in the loops. Thanks :)
- Aaron J.
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/108992/#review27877
-----------------------------------------------------------
On Feb. 22, 2013, 7:17 p.m., Raul Fernandes wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://git.reviewboard.kde.org/r/108992/
> -----------------------------------------------------------
>
> (Updated Feb. 22, 2013, 7:17 p.m.)
>
>
> Review request for Plasma.
>
>
> Description
> -------
>
> - create variables and classes outside the loops
> - reserve space in QList if we know already how many items will be added (avoid \
> unnecessary reallocations)
> - use const_iterator when possible
> - remove a useless call (p->setPen(Qt::NoPen) - it will be set latter before be \
> used)
> - avoid multiplications (x3, x2, x1 and x0)
>
>
> Diffs
> -----
>
> plasma/widgets/signalplotter.cpp 8e9e294
>
> Diff: http://git.reviewboard.kde.org/r/108992/diff/
>
>
> Testing
> -------
>
> I have tested with KDE 4.10 with no problems.
> I have seen a improvement of about 5% in drawPlots() function, the most expensive \
> function in painting.
>
> Thanks,
>
> Raul Fernandes
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="http://git.reviewboard.kde.org/r/108992/">http://git.reviewboard.kde.org/r/108992/</a>
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<br />
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On February 22nd, 2013, 1:32 a.m. UTC, <b>Aaron J. \
Seigo</b> wrote:</p> <blockquote style="margin-left: 1em; border-left: 2px solid \
#d0d0d0; padding-left: 10px;">
<table width="100%" border="0" bgcolor="white" style="border: 1px solid #C0C0C0; \
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<tr>
<th colspan="4" bgcolor="#F0F0F0" style="border-bottom: 1px solid #C0C0C0; \
font-size: 9pt; padding: 4px 8px; text-align: left;"> <a \
href="http://git.reviewboard.kde.org/r/108992/diff/1/?file=114209#file114209line230" \
style="color: black; font-weight: bold; text-decoration: \
underline;">plasma/widgets/signalplotter.cpp</a> <span style="font-weight: normal;">
(Diff revision 1)
</span>
</th>
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</thead>
<tbody style="background-color: #e4d9cb; padding: 4px 8px; text-align: center;">
<tr>
<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">void \
SignalPlotter::reorderPlots(const QList<uint>& newOrder)</pre></td>
</tr>
</tbody>
<tbody>
<tr>
<th bgcolor="#b1ebb0" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2"></font></th> <td bgcolor="#c5ffc4" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "></pre></td> <th \
bgcolor="#b1ebb0" style="border-left: 1px solid #C0C0C0; border-right: 1px solid \
#C0C0C0;" align="right"><font size="2">230</font></th> <td bgcolor="#c5ffc4" \
width="50%"><pre style="font-size: 8pt; line-height: 140%; margin: 0; "> <span \
class="kt">int</span> <span class="n">newIndex</span><span \
class="p">;</span></pre></td> </tr>
</tbody>
</table>
<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">no point in taking PODs \
out of the loop</pre> </blockquote>
<p>On February 22nd, 2013, 7:15 p.m. UTC, <b>Raul Fernandes</b> wrote:</p>
<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">Actually, the benefit \
exists in PODs too (the compiler has to adjust the stack each iteration) but is \
minor. I agree. I don't agree that it uglifies the code or make it less readable.
To me, it doesn't make any difference to readability and has the (little) gain in \
performance. My opinion. </pre>
</blockquote>
</blockquote>
<pre style="margin-left: 1em; white-space: pre-wrap; white-space: -moz-pre-wrap; \
white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">So we have \
a difference in opinion when it comes to readability, and that's what it is: an \
opinion. As the maintainer, my opinion wins in a tie :) My reason for this is that we \
end up with more variables outside the scope they are used which means to understand \
the loop one needs to read more outside the loop, and should other variables of \
similar name appear later on .....
PODs have very, very little overhead and we value the readability over such \
micro-optimizations. to confirm this with actual numbers i wrote a small test program \
that interates 10 million times performing simple math on 6 ints that are declared in \
the loop or out of it. result? neither exceeded 1ms. so in this case, it is not worth \
it.
Conclusion: PODs will remain in the loops. Thanks :)</pre>
<br />
<p>- Aaron J.</p>
<br />
<p>On February 22nd, 2013, 7:17 p.m. UTC, Raul Fernandes wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" \
style="background-image: \
url('http://git.reviewboard.kde.org/static/rb/images/review_request_box_top_bg.ab6f3b1072c9.png'); \
background-position: left top; background-repeat: repeat-x; border: 1px black \
solid;"> <tr>
<td>
<div>Review request for Plasma.</div>
<div>By Raul Fernandes.</div>
<p style="color: grey;"><i>Updated Feb. 22, 2013, 7:17 p.m.</i></p>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Description </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" \
style="border: 1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">- create variables and classes outside the loops
- reserve space in QList if we know already how many items will be added (avoid \
unnecessary reallocations)
- use const_iterator when possible
- remove a useless call (p->setPen(Qt::NoPen) - it will be set latter before be \
used)
- avoid multiplications (x3, x2, x1 and x0)</pre>
</td>
</tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Testing </h1>
<table width="100%" bgcolor="#ffffff" cellspacing="0" cellpadding="10" style="border: \
1px solid #b8b5a0"> <tr>
<td>
<pre style="margin: 0; padding: 0; white-space: pre-wrap; white-space: \
-moz-pre-wrap; white-space: -pre-wrap; white-space: -o-pre-wrap; word-wrap: \
break-word;">I have tested with KDE 4.10 with no problems. I have seen a improvement \
of about 5% in drawPlots() function, the most expensive function in painting.</pre> \
</td> </tr>
</table>
<h1 style="color: #575012; font-size: 10pt; margin-top: 1.5em;">Diffs</b> </h1>
<ul style="margin-left: 3em; padding-left: 0;">
<li>plasma/widgets/signalplotter.cpp <span style="color: grey">(8e9e294)</span></li>
</ul>
<p><a href="http://git.reviewboard.kde.org/r/108992/diff/" style="margin-left: \
3em;">View Diff</a></p>
</td>
</tr>
</table>
</div>
</body>
</html>
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