Mapfile Tuning

[Fawcett, David]

I started a Mapfile Tuning HowTo on the MapServer site.  It is 'public',
but the effective date is set into the future, so it is only visible by
hitting the URL directly. 

http://mapserver.gis.umn.edu/docs/howto/mapfiletuning

I didn't have time to write much this morning, once we have some real
content, it I will make is visible.  

Add your suggestions/contributions for content as comments and I will
compile them.  

David. 

-----Original Message-----
From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
Behalf Of Paul Ramsey
Sent: Tuesday, September 19, 2006 10:31 AM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: Re: [UMN_MAPSERVER-USERS] Mapfile Tuning


We know from experience that the answer is "very expensive".  We had a 
large number of "init=epsg:" references in a mapfile and when we 
converted them to straight proj4 strings realized almost a second in 
speed improvements.

Frank Warmerdam wrote:
> Ed McNierney wrote:
>> I have not found that unnecessary projection definitions are 
>> expensive, but I certainly agree that minimalist mapfiles will save 
>> you a lot of time.
> 
> Ed, others,
> 
> I think a projection block that provides all the parameters should be 
> very "cheap" in processing time, but any time you refer to projection 
> details by EPSG code number, there is a whole file lookup involved.  
> As far as I know cost is paid for each EPSG reference, even if many 
> places refer to the same code.  I would definately like to make some 
> improvements in this regard, likely within PROJ itself.
> 
> It would be interesting to prepare some timetests on this issue to see

> just how significant it is.
> 
> Best regards,