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List: kfm-devel
Subject: Re: Review Request 111398: Fix O(N^2) complexity issue in KItemListView::slotItemsRemoved
From: "Mark Gaiser" <markg85 () gmail ! com>
Date: 2013-07-05 9:43:43
Message-ID: 20130705094343.26116.9490 () vidsolbach ! de
[Download RAW message or body]
> On July 5, 2013, 7:10 a.m., Mark Gaiser wrote:
> > dolphin/src/kitemviews/kitemlistview.cpp, line 1095
> > <http://git.reviewboard.kde.org/r/111398/diff/1/?file=168518#file168518line1095>
> >
> > This if doesn't seem to do anything, only the elseif.. Perhaps just remove it and \
> > end up with:
> > if (i > lastRemovedIndex) {
> > itemsToMove.append(i);
> > continue;
> > }
>
> Frank Reininghaus wrote:
> This 'if' check prevents that items which are *before* the removed range are \
> removed from the view.
No issue then. Although that's only the case if the order of i (thus the order of \
m_visibleItems) can be "random". You probably know best if it is or isn't :)
- Mark
-----------------------------------------------------------
This is an automatically generated e-mail. To reply, visit:
http://git.reviewboard.kde.org/r/111398/#review35613
-----------------------------------------------------------
On July 4, 2013, 10:10 p.m., Frank Reininghaus wrote:
>
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://git.reviewboard.kde.org/r/111398/
> -----------------------------------------------------------
>
> (Updated July 4, 2013, 10:10 p.m.)
>
>
> Review request for Dolphin.
>
>
> Description
> -------
>
> In a directory which is shown in Dolphin, try the following (where N is a large \
> number > 100000):
> touch {1..N}.png
> touch {1..N}.jpg
>
> (wait until all files are shown in the view)
>
> rm *.jpg
>
> This will freeze Dolphin for quite some time (if not, try to increase the number of \
> files). This is because KItemListView::slotItemsRemoved() has a loop over all \
> removed item ranges (100000 in this case), and in each loop, it has another loop \
> that iterates through all items and tries to find visible ones. This is bad because \
> there is always only a small number of visible items, so we better just iterate \
> over those (similar to the approach in KItemListView::slotItemsInserted).
>
> Diffs
> -----
>
> dolphin/src/kitemviews/kitemlistview.cpp 2ea6657
>
> Diff: http://git.reviewboard.kde.org/r/111398/diff/
>
>
> Testing
> -------
>
> Dolphin takes a lot less time to remove many item ranges.
>
>
> Thanks,
>
> Frank Reininghaus
>
>
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This is an automatically generated e-mail. To reply, visit:
<a href="http://git.reviewboard.kde.org/r/111398/">http://git.reviewboard.kde.org/r/111398/</a>
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<blockquote style="margin-left: 1em; border-left: 2px solid #d0d0d0; padding-left: \
10px;"> <p style="margin-top: 0;">On July 5th, 2013, 7:10 a.m. UTC, <b>Mark \
Gaiser</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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<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/111398/diff/1/?file=168518#file168518line1095" \
style="color: black; font-weight: bold; text-decoration: \
underline;">dolphin/src/kitemviews/kitemlistview.cpp</a> <span style="font-weight: \
normal;">
(Diff revision 1)
</span>
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<td colspan="4"><pre style="font-size: 8pt; line-height: 140%; margin: 0; ">void \
KItemListView::slotItemsRemoved(const KItemRangeList& itemRanges)</pre></td>
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<th bgcolor="#e9eaa8" style="border-right: 1px solid #C0C0C0;" \
align="right"><font size="2">1090</font></th> <td bgcolor="#fdfebc" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "> <span \
class="k">if</span> <span class="p">(</span><span class="o"><span \
class="hl">!</span></span><span class="n"><span class="hl">widget</span></span><span \
class="p">)</span> <span class="p">{</span></pre></td> <th bgcolor="#e9eaa8" \
style="border-left: 1px solid #C0C0C0; border-right: 1px solid #C0C0C0;" \
align="right"><font size="2">1088</font></th> <td bgcolor="#fdfebc" width="50%"><pre \
style="font-size: 8pt; line-height: 140%; margin: 0; "> <span \
class="k">if</span> <span class="p">(</span><span class="n"><span \
class="hl">i</span></span><span class="hl"> </span><span class="o"><span \
class="hl"><</span></span><span class="hl"> </span><span class="n"><span \
class="hl">firstRemovedIndex</span></span><span class="p">)</span> <span \
class="p">{</span></pre></td> </tr>
</tbody>
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<pre style="white-space: pre-wrap; white-space: -moz-pre-wrap; white-space: \
-pre-wrap; white-space: -o-pre-wrap; word-wrap: break-word;">This if doesn't seem \
to do anything, only the elseif.. Perhaps just remove it and end up with:
if (i > lastRemovedIndex) {
itemsToMove.append(i);
continue;
}</pre>
</blockquote>
<p>On July 5th, 2013, 9:15 a.m. UTC, <b>Frank Reininghaus</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;">This 'if' check \
prevents that items which are *before* the removed range are removed from the \
view.</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;">No issue \
then. Although that's only the case if the order of i (thus the order of \
m_visibleItems) can be "random". You probably know best if it is or \
isn't :)</pre> <br />
<p>- Mark</p>
<br />
<p>On July 4th, 2013, 10:10 p.m. UTC, Frank Reininghaus wrote:</p>
<table bgcolor="#fefadf" width="100%" cellspacing="0" cellpadding="8" \
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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 Dolphin.</div>
<div>By Frank Reininghaus.</div>
<p style="color: grey;"><i>Updated July 4, 2013, 10:10 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;">In a directory which is shown in Dolphin, try the following (where N is \
a large number > 100000):
touch {1..N}.png
touch {1..N}.jpg
(wait until all files are shown in the view)
rm *.jpg
This will freeze Dolphin for quite some time (if not, try to increase the number of \
files). This is because KItemListView::slotItemsRemoved() has a loop over all removed \
item ranges (100000 in this case), and in each loop, it has another loop that \
iterates through all items and tries to find visible ones. This is bad because there \
is always only a small number of visible items, so we better just iterate over those \
(similar to the approach in KItemListView::slotItemsInserted).</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;">Dolphin takes a lot less time to remove many item ranges.</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>dolphin/src/kitemviews/kitemlistview.cpp <span style="color: \
grey">(2ea6657)</span></li>
</ul>
<p><a href="http://git.reviewboard.kde.org/r/111398/diff/" style="margin-left: \
3em;">View Diff</a></p>
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