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<div class="moz-cite-prefix">Le 23/07/2024 à 21:08, Meyer, Jesse R.
(GSFC-618.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] a écrit :<br>
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<p class="MsoNormal">Excellent, thanks Even! Do you recall what
the runtime was before these changes on your test system?
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I killed the process at about half an hour. Don't recall the
progress it reached, maybe 40%-50%.<br>
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<p class="MsoNormal"><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span
style="color:black">From:
</span></b><span style="color:black">Even Rouault
<a class="moz-txt-link-rfc2396E" href="mailto:even.rouault@spatialys.com"><even.rouault@spatialys.com></a><br>
<b>Date: </b>Tuesday, July 23, 2024 at 3:00</span><span
style="font-family:"Arial",sans-serif;color:black"> </span><span
style="color:black">PM<br>
<b>To: </b>Meyer, Jesse R. (GSFC-618.0)[SCIENCE
SYSTEMS AND APPLICATIONS INC]
<a class="moz-txt-link-rfc2396E" href="mailto:jesse.r.meyer@nasa.gov"><jesse.r.meyer@nasa.gov></a>, Meyer, Jesse R.
(GSFC-618.0)[SCIENCE SYSTEMS AND APPLICATIONS INC] via
gdal-dev <a class="moz-txt-link-rfc2396E" href="mailto:gdal-dev@lists.osgeo.org"><gdal-dev@lists.osgeo.org></a><br>
<b>Subject: </b>[EXTERNAL] Re: [gdal-dev] Expected
runtime of polygonize (GDAL 3.9.0) for few very large
features.</span><span
style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
<br>
<o:p></o:p></p>
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<p>Hi,<o:p></o:p></p>
<p>I've got a chance to have a look at your test dataset.
In <a href="https://github.com/OSGeo/gdal/pull/10477"
moz-do-not-send="true" class="moz-txt-link-freetext">
https://github.com/OSGeo/gdal/pull/10477</a>, I've
reduced the runtime to 8 minutes (with GeoParquet
output, without spatial sorting), by optimizing some
implementation details. I believe this could be further
reduced as most of the time is still spent in
malloc/free of temporary objects (the output is 90
million polygons!) and some objects could be reused, but
that would be more extensive changes<o:p></o:p></p>
<p>Even<o:p></o:p></p>
<div>
<p class="MsoNormal">Le 01/07/2024 à 18:40, Meyer, Jesse
R. (GSFC-618.0)[SCIENCE SYSTEMS AND APPLICATIONS INC]
via gdal-dev a écrit :<o:p></o:p></p>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We’ve encountered a few images
with what seems like pathological performance
problems with polygonise. The details below are a
report from another developer that I haven’t yet
independently verified.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We threshold a raster image to a
binary mask in a memory dataset, use that as its own
mask to mask out the background.<o:p></o:p></p>
<p class="MsoNormal">gdal.Polygonize(nn_mem_band,
nn_mem_band, ogr_mem_lyr, -1)<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">We have a number of 32k x 32k
raster images that feature number of very large
same-valued regions (some as large as 80% of the
entire raster). We’re seeing ~10hrs on a modern
workstation to complete the line of code above.
OpenCV can apparently construct a connected
components list in mere seconds, on the same
workstation and image, so we’re considering
constructing the OGR geometries directly from those
as a temporary work around.<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">Is this situation a known pitfall
with the current algorithm / data structures behind
Polygonize?<o:p></o:p></p>
<p class="MsoNormal"> <o:p></o:p></p>
<p class="MsoNormal">I’m able to share the problematic
tile(s) if of interest,<o:p></o:p></p>
<p class="MsoNormal">Best<o:p></o:p></p>
<p class="MsoNormal">Jesse<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:12.0pt"><br>
<br>
<o:p></o:p></span></p>
<pre>_______________________________________________<o:p></o:p></pre>
<pre>gdal-dev mailing list<o:p></o:p></pre>
<pre><a href="mailto:gdal-dev@lists.osgeo.org"
moz-do-not-send="true" class="moz-txt-link-freetext">gdal-dev@lists.osgeo.org</a><o:p></o:p></pre>
<pre><a
href="https://lists.osgeo.org/mailman/listinfo/gdal-dev"
moz-do-not-send="true" class="moz-txt-link-freetext">https://lists.osgeo.org/mailman/listinfo/gdal-dev</a><o:p></o:p></pre>
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<pre>-- <o:p></o:p></pre>
<pre><a href="http://www.spatialys.com/"
moz-do-not-send="true" class="moz-txt-link-freetext">http://www.spatialys.com</a><o:p></o:p></pre>
<pre>My software is free, but my time generally not.<o:p></o:p></pre>
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<pre class="moz-signature" cols="72">--
<a class="moz-txt-link-freetext" href="http://www.spatialys.com">http://www.spatialys.com</a>
My software is free, but my time generally not.</pre>
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