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Thanks, David. I will try if this will bring some significant
performance boost ...<br>
Tobi<br>
<br>
===<br>
Am 28.07.10 16:09, schrieb Fawcett, David (MPCA):
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<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">I
don’t know anything about your work flow, but if
possible, you could add a pre-processing step where you use a script to
read
your text file and pre-classify the data. You would end up with
integers representing
each class as ‘cell’ values. <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Instead
of :<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">EXPRESSION</span>([pixel]
>= -4 AND [pixel] < -3)<span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">You
could have: EXPRESSION “2” <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Or
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">EXPRESSION
/2/<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">Matching
a single string should be the fastest expression to
evaluate.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);">David.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size: 11pt; font-family: "Calibri","sans-serif"; color: rgb(31, 73, 125);"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">From:</span></b><span
style="font-size: 10pt; font-family: "Tahoma","sans-serif"; color: windowtext;">
<a class="moz-txt-link-abbreviated" href="mailto:mapserver-users-bounces@lists.osgeo.org">mapserver-users-bounces@lists.osgeo.org</a>
[<a class="moz-txt-link-freetext" href="mailto:mapserver-users-bounces@lists.osgeo.org">mailto:mapserver-users-bounces@lists.osgeo.org</a>] <b>On Behalf Of </b>Tobias
Weiß<br>
<b>Sent:</b> Wednesday, July 28, 2010 8:25 AM<br>
<b>To:</b> <a class="moz-txt-link-abbreviated" href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><br>
<b>Subject:</b> Re: [mapserver-users] Raster data performance<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hi Alex,<br>
<br>
I tried some of the performance tips you mentioned, e.g. converted the
.txt to
a tiled TIFF to optimize performance. I can not see significant
changes
in rendering speed.<br>
<br>
gdal_translate -co TILED=YES input.txt output.tif<br>
<br>
The major brake still is the expression stuff. I really wonder what
makes this
task so time-consuming, it should not be more than a simple comparison.<br>
<br>
Do you have experiences with this issue? Or do I have to live with this
constraint?<br>
<br>
Best, Tobi<br>
<br>
===<br>
Am 28.07.10 14:27, schrieb Alexandre Dube: <o:p></o:p></p>
<p class="MsoNormal">Hi Tobi,<br>
<br>
The following documentation topics about raster might help :<br>
<br>
<a moz-do-not-send="true"
href="http://mapserver.org/input/raster.html#rasters-and-tile-indexing">http://mapserver.org/input/raster.html#rasters-and-tile-indexing</a><br>
<a moz-do-not-send="true"
href="http://mapserver.org/input/raster.html#raster-display-performance-tips">http://mapserver.org/input/raster.html#raster-display-performance-tips</a><br>
<br>
and about expressions :<br>
<br>
<a moz-do-not-send="true"
href="http://mapserver.org/mapfile/expressions.html">http://mapserver.org/mapfile/expressions.html</a><br>
<br>
The string comparison type is the fastest, so you could try define
more
classes but using string comparison to see if it gets faster. Also, a
good performance tip is to put your most frequent classes types on top
first. For example, if 80% of your data has "pixel = -3" then
put it on top.<br>
<br>
Kind regards,<br>
<br>
Alexandre<br>
<br>
<br>
On 10-07-28 04:54 AM, Tobias Weiß wrote: <o:p></o:p></p>
<p class="MsoNormal"><span style="font-family: "Tahoma","sans-serif";">Hello
list,<br>
<br>
this is my first email to this list. I am working with MapServer,
OpenLayers
& TileCache for almost 1 year now and the tools are really working
great
together, when everything is configured correctly ;-)<br>
<br>
At the moment I´m facing a performance problem with raster data that
serves as
input data to render my map tiles. The spatial resolution of this
raster data
is 720 (rows) x 360 (cols) and it is stored in a simple .txt file (The
size of
the file is around 2 MB). I use TileCache to prerender maptiles for
different
zoom levels that are later displayed in a web application using
OpenLayers.<br>
<br>
I discovered, that the rendering speed of MapServer seems to mainly
depend on
how many different classes I define within my mapfile, meaning how many
expressions MapServer has to evaluate during the rendering process.
Without any
classes MapServer the rendering speed is really fast, the more classes
I use the
slower it gets. With e.g. 10 different classes defining 10 different
styles /
pixel colors the rendering time for one tile can increase up to 60 sec.<br>
<br>
<br>
</span><o:p></o:p></p>
<pre>CLASS<span class="moz-txt-citetags"><o:p></o:p></span></pre>
<pre><span class="moz-txt-citetags"> </span>EXPRESSION ([pixel] >= -4 AND [pixel] < -3)<span
class="moz-txt-citetags"><o:p></o:p></span></pre>
<pre><span class="moz-txt-citetags"> </span>STYLE<o:p></o:p></pre>
<pre> COLOR 69 117 180<o:p></o:p></pre>
<pre> END<o:p></o:p></pre>
<pre>END<o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<p class="MsoNormal"><br>
<span style="font-family: "Tahoma","sans-serif";">While working with
shape files
I haven´t had this problems and prerendering map tiles was really fast.
With
raster data the rendering time for one map and 5 different zoom levels
can take
up to several hours and almost overburdens my CPU.<br>
<br>
Can anybody give me a hint how I could improve this?<br>
<br>
Best, Tobi<br>
<br>
</span><o:p></o:p></p>
<pre><o:p> </o:p></pre>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>mapserver-users mailing list<o:p></o:p></pre>
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<pre> <o:p></o:p></pre>
<p class="MsoNormal"><br>
<br>
<br>
<o:p></o:p></p>
<pre>-- <o:p></o:p></pre>
<pre>Alexandre Dubé<o:p></o:p></pre>
<pre>Mapgears<o:p></o:p></pre>
<pre><a moz-do-not-send="true" href="http://www.mapgears.com">www.mapgears.com</a><o:p></o:p></pre>
<pre> <o:p></o:p></pre>
<pre><o:p> </o:p></pre>
<pre><o:p> </o:p></pre>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>mapserver-users mailing list<o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="mailto:mapserver-users@lists.osgeo.org">mapserver-users@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a moz-do-not-send="true"
href="http://lists.osgeo.org/mailman/listinfo/mapserver-users">http://lists.osgeo.org/mailman/listinfo/mapserver-users</a><o:p></o:p></pre>
<pre> <o:p></o:p></pre>
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<br>
<br>
<pre class="moz-signature" cols="72">--
Dipl.-Ing. Tobias Weiß
Potsdam Institute for Climate Impact Research
Pappelallee 20, Room 316
14469 Potsdam
Germany
Phone: +49 / (0)331 / 288-2490
Location: <a class="moz-txt-link-freetext" href="http://bit.ly/1gOr64">http://bit.ly/1gOr64</a></pre>
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