[mapserver-users] Display performance

[Rahkonen Jukka]

Hi,
 
I took some numbers to compare with.
 
Material and methods
 
Polygon layer, rather simple polygons with few vertises, Feature Count: 117383
DEBUG 5 in mapfile
WMS client asks for the whole layer
Mapserver 5.2.1 (CGI) on not so fast Windows computer

Results
First request: rendering time taken from the log file are between 3.5 and 4.5 seconds
Following request, BBOX is changing but all the polygons are drawn though:  rendering times 1.5 - 2.5 seconds
 
Conclusions and discussion
At first one might think that my server is faster.  But this test is not controlled at all because we are not using the same shapefiles and we can't say so. What we can say that a couple of hundred of thousand polygons can be drawn faster.  
 
However, it does not really make sense to render an image this way if it should be fast.  If the screen has 1000 by 1000 pixels it makes a million pixels together.  For 200000 polygons it makes 5 pixels per polygon.  You can simplify your polygon geometries pretty much before anybody can see the differense.  If the polygons are spread evenly nobody can even see the difference if there are 20000 or 200000 polygons on the screen.
 
We have one polygon layer with about million polygons and for that I made two simplified layers which contain only 1 percent and 10 percent of all the polygons.  Those and the original shapefile are put into the same scale dependent WMS GROUP layer. This group is pretty fast at any scale.  The 1 percent layer is perhaps a bit too sparse but I have been too lazy to have a try with 2 or 5 percent samples.
 
-Jukka Rahkonen-
 
________________________________

Lähettäjä: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] Puolesta Chris Jackson
Lähetetty: 2. syyskuuta 2010 23:03
Vastaanottaja: Lime, Steve D (DNR)
Kopio: mapserver-users at lists.osgeo.org
Aihe: Re: [mapserver-users] Display performance



	Steve
	
	That saves some work, but how long would you expect one that size to load?  I have just realised (admittedly not looked at the data for a couple of years) that it is actually 170,000 records - takes about 20 secs to load - sound reasonable?
	
	Chris
	
	
	On 2 September 2010 20:50, Lime, Steve D (DNR) <Steve.Lime at state.mn.us> wrote:
	

		That's not that big a dataset. Probably faster from a local shapefile.

		 

		Steve

		 

		From: mapserver-users-bounces at lists.osgeo.org [mailto:mapserver-users-bounces at lists.osgeo.org] On Behalf Of Chris Jackson
		Sent: Thursday, September 02, 2010 2:29 PM
		To: mapserver-users at lists.osgeo.org
		Subject: [mapserver-users] Display performance

		 

		Hi
		
		I wondered if anyone knew if displaying a 50,000 polygon dataset would be significantly faster if called from a database rather than a spatially indexed shapefile, or is it a similar overhead for both. 
		Thanks
		Chris


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