[Mapserver-users] classification performance

[Bart van den Eijnden]

Hi Steve,

thanks for your answer. I am gonna do a little investigation with the 
pointers you gave me.

Are there any tools out there for this kind of analysis?

Or should I just put my data in PostGIS and write queries (and a procedure 
to create the classification ahead)?

Best regards,
Bart

On Thu, 22 Jul 2004 11:17:20 -0500, Steve Lime 
<steve.lime at dnr.state.mn.us> wrote:

> I don't know if it's expected but it's not all that suprising. I'd be
> curious for a bit
> more detail. For example:
>
>  - how many features are in the bbox
>  - how many features in the shapefile
>  - average feature complexity (nverts)
>  - distribution of classes in the bbox
>  - the actual listing of expressions (layer definition)
>
> The order that classes are defined may have a siginificant impact on
> performance,
> especially in a case like yours. For example, let's say that the bulk
> of the features
> match class 27. That means that the first 26 expression tests all
> failed. So it's not
> just a case of one feature means one expression test, it can be much
> worse.
>
> Pre-classifying your date, either splitting into seperate shapefiles,
> or applying the
> expressions AHEAD of time (so you can use string expressions) can
> really help.
>
> Steve
>
>>>> <bartvde at xs4all.nl> 7/22/2004 6:51:32 AM >>>
> Hi list,
>
> I have been doing some performance tests this morning on a shapefile
> and a
> tiled version of the same shapefile. The most astonishing outcome for
> me
> was however the amount of time a classifcation takes. I have a pretty
> complex classification for my dataset with 28 classes, mostly using
> regular expressions.
>
> Here are the results of the test (Intel Xeon 2,4 Ghz, 1,5 Gb memory,
> Windows 2000 Server), tests performed with Microsoft Web Application
> Stress Tool on the same server, during 1 minute of continuous
> requests:
>
> 1 Shapefile (1,6 Gb) "without" classification (1 class): 1.4 sec
> Tiled shapefiles in 10x10 (=100) tiles without classification: 0.7 sec
> 1 Shapefile (1,6 Gb) with classification: 2.4 sec
> Tiled shapefiles in 10x10 (=100) tiles with classification: 1.9 sec
>
> So executing the classification on the dataset costs approximately
> 1-1.2
> seconds, which is a more than reading the data in the case of a tiled
> dataset. *** Is this to be expected? ***
>
> bbox used: 160000,445000,170000,455000 (10.000 x 10.000 m)
> image dimensions: 750x750 pixels
> WMS protocol
>
> Best regards,
> Bart
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