[mapserver-users] Corrupt image output

[Mike Leahy]

Hello list,

I'm wondering if anyone can help me figure out a problem I'm having with 
corrupted output from from a tiled geotiff dataset I'm using in a ka-Map 
environment.  You can see what's happening to the imagery here: 
http://img527.imageshack.us/my.php?image=corrupthd1.png

This generally happens when I'm zoomed in fairly close, and usually with 
this high-resolution image dataset.  However, I can get corrupted output 
for other raster datasets (all geotiff, but not always tiled).  It seems 
to happen when the machine is processing most intensively (i.e., usually 
when the imagery is being rendered by ka-Map).  It also seems to be 
limited to the laptop I am using, which is running F7-x86_64.  In 
contrast, I have an actual server (F8-x86_64), which has a virtually 
identical setup (with respect to MapServer and its various 
dependencies), but with lots more cpu cores and ram, and it's having no 
trouble at all (as far as I have noticed).

The corruption in the output from the same application my laptop is not 
always the same - if I clear the cache for ka-Map and re-render the 
images, I'll get similar artifacts appearing in the output (red, green, 
blue and/or black rectangles), but they will vary in size and location. 
  It happens for both GD/AGG drivers, and JPEG/PNG output formats.

Until now, I figured it was just a problem with limited memory on my 
laptop (it was always around 100% when rendering this imagery on the web 
service + viewing the application in a browser), but now I've upgraded 
the ram - there's plenty of spare room and I'm still getting the same 
problem.  I just finished upgrading Gdal from 1.5.0 to 1.5.2, and that 
didn't help any.

Basically, the only real differences I can think of between my laptop 
and my server are the number of cpu cores (1 on my laptop vs. 8 on the 
server), and possibly the versions of some of the underlying libraries 
in the system.  Does anyone know where I should start looking to find 
the cause of this?  Or perhaps somebody recognizes this problem, and 
knows what I might be doing wrong...

Thanks for any suggestions,
Mike